Immunology and Serology MCQs with Answer and Explanations | Chapter 8

Answer: IgE

Reaginic antibodies are a type of antibody known as immunoglobulin E (IgE). These antibodies play a key role in allergic reactions by binding to mast cells and basophils, which then release histamine and other chemicals that trigger allergy symptoms like runny nose, itchy eyes, and wheezing.

The other options are incorrect:

• IgG: IgG is the most common antibody in the blood, but it is not involved in allergic reactions.
• IgA: IgA is another type of antibody found in mucous membranes and saliva. It helps defend against infections but is not associated with allergies.
• IgM: IgM is the first antibody produced in response to an infection. It is not typically involved in allergies.

Answer: Isospecific

Blood group antigens are isospecific, meaning they are specific to individuals within the same species. These antigens are found on the surface of red blood cells and determine an individual’s blood group, such as A, B, AB, or O.

The other options are incorrect:

• Species specific: While some antigens may show some degree of species specificity, blood group antigens are primarily relevant within a species, allowing for compatible blood transfusions between individuals of the same species.
• Autospecific: Autospecific refers to antigens that react with antibodies from the same individual, which would cause an autoimmune reaction. Blood group antigens are not self-reactive and do not trigger such responses in a healthy individual.
• Organ specific: While some antigens are specific to certain organs, blood group antigens are present on red blood cells throughout the body, not confined to a particular organ.

Answer: Precipitation

The reaction of a soluble antigen with its specific antibody leading to the formation of an insoluble complex that can precipitate out of solution is known as precipitation. This occurs when the antigen and antibody are in optimal proportions, forming a lattice that results in visible precipitates.

The other options are incorrect:

• Flocculation: Flocculation is similar to precipitation but refers to the formation of loose, clumpy aggregates. While it can occur in antigen-antibody reactions, it’s not as specific as precipitation.
• Agglutination: Agglutination involves the clumping of particles like bacteria or red blood cells when they are coated with antibodies. This reaction is used in blood typing and other diagnostic tests, but it’s not the term used for soluble antigen-antibody interaction.
• Complement fixation: Complement fixation is another type of antigen-antibody reaction where a group of blood proteins (complement system) gets activated and attaches to the immune complex. This can lead to various outcomes like cell lysis (destruction), but it’s not the primary mechanism involved in precipitation.

Answer: Glycoprotein

Interferons are a group of glycoproteins, meaning they are proteins with attached sugar molecules (glycans). These sugar chains play a role in the stability, folding, and function of interferons, allowing them to interact with their target receptors on cells.

The other options are incorrect:

• Lipids: Lipids are a class of fatty acid-based molecules that do not contain protein structures and are not involved in interferon composition.
• Lipoprotein: Lipoproteins are complexes of lipids and proteins, but the protein component in these molecules serves mainly for transport, not cellular signaling like interferons.
• Nucleic Acid: Nucleic acids (DNA and RNA) are the genetic material of cells. Interferons are not genetic material but rather signaling molecules produced by cells.

Answer: IgM

Agglutination reactions are strongest with IgM because IgM has a pentameric structure, giving it ten antigen-binding sites, which greatly enhances its ability to cross-link antigens and form visible clumps, making it highly effective in agglutination.

The other options are incorrect:

• IgG: IgG is the most abundant antibody but exists as a monomer (single unit). While it can participate in agglutination, its smaller size and fewer binding sites limit its strength compared to IgM.
• IgA: IgA exists in various forms, including a dimer (two units) in mucosal secretions. While it can agglutinate pathogens, its structure is not as efficient for this process compared to IgM.
• IgD: IgD is present in very low amounts and primarily functions as a B cell receptor, not participating significantly in agglutination reactions.

Answer: Immunotherapy

Monoclonal antibodies are used in immunotherapy, which involves using these antibodies to target specific antigens found on the surface of pathogens or cancer cells. This helps the immune system recognize and destroy these cells more effectively.

The other options are incorrect:

• Gene therapy: Gene therapy involves modifying a patient’s genes to treat a disease. Monoclonal antibodies do not alter genes, they target specific molecules.
• Blood transfusion: Blood transfusions involve introducing blood from a compatible donor into a recipient’s circulation. Monoclonal antibodies are not whole blood but isolated proteins.
• Organ transfusion: Organ transplants involve transferring a healthy organ from a donor to a recipient. Monoclonal antibodies are not entire organs but laboratory-produced proteins.

Answer: Monoclonal antibodies

The hybridoma technique is specifically designed to produce monoclonal antibodies. This technique involves fusing an antibody-producing B cell with a myeloma cancer cell. The resulting hybridoma cell line can continuously produce large quantities of a single, identical antibody (monoclonal) specific to the antigen the B cell was originally exposed to.

The other options are incorrect:

• Polyclonal antibodies: Polyclonal antibodies are produced by a variety of B cell lines in response to an antigen. They are not derived from a single hybridoma cell line.
• Both a and b: As explained above, hybridoma technique is specific for monoclonal antibody production.
• None of these: The hybridoma technique is a well-established method for creating monoclonal antibodies.

Answer: ELISA

ELISA is a versatile immunoassay technique commonly used to detect HIV infection. It can identify HIV antibodies or viral antigens in a blood sample. ELISA offers high sensitivity and specificity, making it a reliable tool for HIV diagnosis.

The other options are incorrect:

• Widal test: The Widal test is used to diagnose typhoid fever by detecting specific antibodies against Salmonella typhi bacteria. It’s not used for HIV.
• Agglutination: Agglutination is a general term for clumping of particles like cells or bacteria caused by antibodies. While agglutination reactions are used in some immunoassays, it’s not specific to HIV testing.
• CFT (Complement Fixation Test): CFT is an older serological test used for various infections, but it’s not commonly used for modern HIV diagnosis due to the availability of more specific and sensitive tests like ELISA.

Answer: IgM

IgM has the highest valency among antibodies. Valency refers to the number of antigen-binding sites. IgM is a pentamer, meaning it has five subunits, each with two antigen-binding sites, giving it a total of ten binding sites.

The other options are incorrect:

• IgG: IgG is the most abundant antibody but exists as a monomer (single unit) with two antigen-binding sites.
• IgA: IgA can exist as a monomer or dimer (two units) with two or four antigen-binding sites, respectively. While it can participate in some agglutination reactions, its valency is lower than IgM.
• IgD: IgD is present in very low amounts and primarily functions as a B cell receptor, not having a significant role in antigen binding or agglutination. It has only one antigen-binding site.

Answer: Affiniy

Affinity refers to the strength of the individual interaction between a single antigen-binding site on an antibody and its specific epitope (the complementary region) on an antigen molecule. It reflects the inherent attraction between these two structures. A higher affinity signifies a stronger and more specific binding interaction.

The other options are incorrect:

• Avidity: Avidity describes the overall strength of an antibody-antigen complex, considering the combined effect of affinity and the number of binding sites involved. For example, an antibody with multiple binding sites (like IgM) can have high avidity even if the individual affinity of each site is moderate.
• Reaction: Reaction is a broader term encompassing the interaction between molecules, not specific to the strength of the binding.
• None of these: Affinity is a well-established concept in immunology specifically referring to the strength of an individual antigen-antibody interaction.

Answer: Infection

Active immunity is induced by exposure to a pathogen, either through infection or vaccination. Infection triggers the body’s immune response, leading to the production of antibodies and memory cells that provide long-lasting immunity against the specific pathogen.

The other options are incorrect:

• Placental transfer of antibodies: This is an example of passive immunity, where antibodies from the mother are transferred to the baby through the placenta. This provides temporary protection for the newborn but doesn’t stimulate the baby’s own immune system to develop long-term immunity.
• Injection of antibodies: Injecting pre-made antibodies (e.g., immune globulin) can provide short-term passive immunity but doesn’t trigger the immune system to develop its own memory and long-term protection.
• Injection of gamma-globulins: Gamma globulin is a blood product containing various antibodies. Similar to injecting antibodies, it offers temporary passive immunity but doesn’t induce active immunity.

Answer: Contact dermatitis

Delayed-type hypersensitivity (DTH) is a type of immune response that typically develops several hours to days after exposure to an antigen. Contact dermatitis, such as poison ivy rash, is a classic example of a DTH reaction where skin inflammation occurs hours after contact with the offending substance.

The other options are incorrect:

• Penicillin allergy: Penicillin allergy is an example of an immediate hypersensitivity reaction (type I). It involves IgE antibodies and mast cell activation, leading to rapid symptoms like rash, wheezing, or anaphylaxis within minutes of exposure.
• Arthus reaction: This is another type of hypersensitivity reaction (type III) involving immune complexes and inflammation. It can occur a few hours after exposure and is less common than DTH.
• Anaphylaxis: Anaphylaxis is a severe, potentially life-threatening allergic reaction that can involve multiple organ systems and rapid onset of symptoms. It’s a type I hypersensitivity reaction similar to penicillin allergy.

Answer: All of the above

Antibody formation is a complex process influenced by several factors:

• Age: Newborns have limited antibody production due to an immature immune system. As a person ages, their immune response becomes more robust, but it can also decline in the elderly.
• Amount of antigen: The quantity of antigen exposure affects antibody production. A higher dose generally leads to a stronger and faster antibody response.
• Well being of the person: Overall health and nutritional status can significantly impact the immune system’s ability to generate antibodies. Factors like malnutrition, fatigue, or underlying illnesses can weaken the response.

Answer: All of these

Local immunity plays a crucial role in defending against various conditions at the initial site of exposure:

• Influenza: The respiratory tract is the primary entry point for the influenza virus. Local mucosal immunity, including secretory IgA antibodies and immune cells in the respiratory tract lining, help prevent the virus from establishing itself and spreading throughout the body.
• Allergy: Allergens often enter the body through the respiratory tract or skin. Local immune responses, including mast cells and IgE antibodies, can trigger allergic reactions at these sites (runny nose, itchy eyes, skin inflammation).
• Polio: The poliovirus typically enters through the mouth. Local immune responses in the gut can help prevent the virus from establishing itself and spreading to the nervous system.

Answer: Thymus

T-cells, also known as T lymphocytes, are produced from precursor cells in the bone marrow but undergo maturation and differentiation in the thymus gland. The thymus is where T-cells undergo selection and education to develop into functional immune cells capable of recognizing foreign antigens.

The other options are incorrect:

• Bone marrow: While T-cell precursors originate from the bone marrow, their maturation and differentiation occur primarily in the thymus gland. The bone marrow produces hematopoietic stem cells, which can give rise to both T-cells and B-cells.
• Spleen: The spleen is an important organ in the immune system, primarily involved in filtering blood and removing old or damaged red blood cells. However, T-cell production does not occur in the spleen

Answer: B-cells

Antibodies, also known as immunoglobulins, are specialized proteins produced by B-cells (B lymphocytes) of the immune system. When a B cell encounters a specific antigen (foreign molecule), it becomes activated and differentiates into plasma cells. These plasma cells are factories that churn out large quantities of antibodies tailored to that specific antigen.

The other options are incorrect:

• T-cells: T-cells are another type of lymphocyte but play a different role in immunity. They are involved in cell-mediated immunity, directly attacking infected cells or regulating the immune response.
• γ-cells (Gamma cells): There’s no cell type commonly referred to as “gamma cells” in the immune system. Perhaps you meant NK cells?
• NK cells (Natural Killer cells): NK cells are immune system defenders that can directly kill virus-infected cells or tumor cells. They don’t produce antibodies.
• Eosinophils: Eosinophils are white blood cells involved in allergic reactions and defense against parasitic infections. They don’t produce antibodies.

Answer: Haptens

Haptens are incomplete antigens. They are typically small molecules that can bind to specific receptors (antibodies) but lack the size or structure necessary to trigger an immune response by themselves. For a complete immune response, haptens need to be coupled to a larger carrier molecule (often a protein) that can be recognized by the immune system.

The other options are incorrect:

• Immunogens: Immunogens are complete antigens that can stimulate the immune system to produce antibodies. They possess the necessary size and structure to be recognized and elicit an immune response.
• Epitopes: Epitopes are specific regions on an antigen molecule that antibodies bind to. They are part of a complete antigen, not an incomplete one.
• Paratope: The paratope is the complementary region on an antibody molecule that specifically binds to an epitope on an antigen. It’s not a type of antigen itself.

Answer: Both a and b

For a molecule to be an antigen, it generally needs to have both high molecular weight and chemical complexity. High molecular weight ensures that the molecule is large enough to be recognized by the immune system, while chemical complexity provides multiple epitopes for binding to antibodies or T-cell receptors.

The other options are incorrect:

• High molecular weight: While high molecular weight is important for an antigen, it alone is not sufficient. Antigens also require chemical complexity, which provides the diverse structures necessary for immune recognition.
• Chemical complexity: Chemical complexity is crucial for an antigen’s ability to elicit an immune response. However, it alone may not be enough if the molecule is too small or lacks sufficient molecular weight to be recognized effectively by the immune system.
• None of these: This option is incorrect as both high molecular weight and chemical complexity are essential characteristics for a molecule to be an antigen.

Answer: Lymph nodes

Lymph nodes are the primary structures responsible for filtering lymph fluid. They are stationed strategically throughout the lymphatic system and contain immune cells that trap and destroy pathogens (viruses, bacteria, etc.) carried in the lymph.

The other options are incorrect:

• Spleen: The spleen is an immune organ that plays a role in filtering blood, not lymph. It removes old or damaged red blood cells, stores blood platelets, and helps activate the immune response.
• Thymus: The thymus is an essential organ for T cell development and maturation, but it’s not involved in lymph filtration.
• Bone marrow: Bone marrow is the site of blood cell production, including lymphocytes. While it contributes to the immune system, it doesn’t directly filter lymph fluid.

Answer: Lymphocytes

Lymphocytes are the primary cells involved in the immune response. They include B-cells, T-cells, and natural killer (NK) cells. B-cells are responsible for producing antibodies, while T-cells play various roles, including directly killing infected cells and regulating immune responses. NK cells are involved in recognizing and destroying abnormal cells, such as virus-infected cells and tumor cells.

The other options are incorrect:

• NK-cells (Natural Killer cells): NK cells are immune system defenders that can directly kill virus-infected cells or tumor cells. However, they are not part of the adaptive immune response and don’t involve the high degree of antigen specificity seen in lymphocytes.
• K-cells (Killer cells): There’s no distinct cell type commonly referred to as “K-cells” in the immune system. Perhaps you meant NK cells?
• None of these: Lymphocytes are widely recognized as the cornerstone of the adaptive immune response.

Answer: B-cells.

Plasma cells are the terminally differentiated (end stage) form of B-cells. When a B cell encounters a specific antigen (foreign molecule) and becomes activated, it undergoes further differentiation and matures into a plasma cell.

The other options are incorrect:

• T-cells: T-cells are another type of lymphocyte but follow a different maturation pathway and don’t become plasma cells. They are involved in cell-mediated immunity, directly attacking infected cells or regulating the immune response.
• Killer cells: This term can refer to cytotoxic T cells, a type of T cell that directly kills infected cells. They are not plasma cells.
• NK-cells (Natural Killer cells): NK cells are immune system defenders that can directly kill virus-infected cells or tumor cells. They are not related to plasma cells and don’t produce antibodies.

Answer: IgE

Basophils are immune cells that play a role in allergic reactions. They have high-affinity receptors for IgE (immunoglobulin E) antibodies on their surface. When IgE binds to an antigen (allergen), it triggers the release of inflammatory mediators from basophils, including histamine. Histamine causes the symptoms commonly associated with allergies, such as runny nose, itchy eyes, and swelling.

The other options are incorrect:

• IgG: IgG is the most common antibody in the blood but is not involved in activating basophils.
• IgA: IgA is another type of antibody found in mucous membranes and saliva. It is not typically associated with basophil activation.
• IgM: IgM is the first antibody produced in response to an infection. It is not involved in basophil activation related to allergies.

Answer: Hidden epitopes

Denaturation disrupts the three-dimensional structure of a protein antigen. This can expose previously hidden regions of the antigen molecule, making them accessible to the immune system. These newly exposed regions are called hidden epitopes.

The other options are incorrect:

• Cross-reactive antigens: These are antigens from different sources that share similar structural features and can be recognized by the same antibodies. Denaturation doesn’t necessarily create cross-reactive antigens.
• Epitopes: Epitopes are the specific regions on an antigen molecule that antibodies bind to. They can be hidden or exposed depending on the antigen’s conformation, but denaturation can expose hidden ones.
• Forssman antigens: These are a specific type of antigen found in some bacteria that can cross-react with antibodies against human red blood cells. Denaturation wouldn’t necessarily convert an antigen into a Forssman antigen.

Answer: Steric configuration

Antigenic specificity, the ability of an antigen to bind specifically to an antibody or T-cell receptor, is primarily due to the steric configuration or three-dimensional shape of the antigen. The unique arrangement of atoms and functional groups on the antigen’s surface determines its ability to interact with complementary binding sites on antibodies or T-cell receptors.

The other options are incorrect:

• Chemical complexity: Chemical complexity can contribute to the diversity of epitopes on an antigen, but it is not the primary determinant of antigenic specificity. Even simple molecules can have specific steric configurations that confer antigenic specificity.
• Solubility: Solubility refers to the ability of a substance to dissolve in a solvent. While solubility can influence the accessibility of antigens to the immune system, it does not directly determine antigenic specificity.
• All of these: While chemical complexity and solubility may contribute to the overall characteristics of an antigen, antigenic specificity is primarily due to steric configuration. Therefore, selecting “All of these” is incorrect as it overgeneralizes the factors influencing antigenic specificity.

Answer: Glycoproteins

Antibodies, also known as immunoglobulins (Ig), are proteins produced by B-cells of the immune system in response to the presence of foreign substances called antigens. They are glycoproteins, meaning they consist of both protein and carbohydrate moieties.

The other options are incorrect:

• Proteins: While antibodies are primarily composed of protein chains, the presence of glycans makes them glycoproteins.
• Phospholipids: Phospholipids are a different class of biomolecules that form the major component of cell membranes. They are not involved in antibody structure.
• None of these: Antibodies are well-established to be glycoproteins.

Answer: IgG

IgG antibodies are considered general-purpose antibodies because they are the most abundant type of antibody in the bloodstream and provide long-term immunity against bacterial and viral infections. They can cross the placenta, providing passive immunity to newborns, and are involved in various immune functions such as neutralization, opsonization, and complement activation.

The other options are incorrect:

• IgA: IgA antibodies are primarily found in mucosal secretions, such as saliva, tears, and breast milk. While they play a crucial role in mucosal immunity, they are not considered general-purpose antibodies like IgG.
• IgM: IgM antibodies are the first antibodies produced during the primary immune response to an infection. They are efficient at agglutination and complement activation but are not as versatile as IgG antibodies in terms of long-term immunity and immune functions.
• IgD: IgD antibodies are found on the surface of mature B-cells and play a role in the activation of B-cells. They are not secreted in large quantities like IgG and are not considered general-purpose antibodies.

Answer: IgA

Colostrum, the first milk produced by mothers after childbirth, is rich in antibodies to protect the newborn baby’s developing immune system. Among all the antibody types, IgA is the predominant immunoglobulin present in colostrum.

The other options are incorrect:

• IgG: IgG is the most abundant antibody type in the blood but is not the primary antibody found in colostrum.
• IgM: IgM is the first antibody produced during an immune response but is not efficiently transferred through breast milk.
• IgE: IgE antibodies are involved in allergic reactions and are not present in significant amounts in colostrum.

Answer: IgM

IgM is often referred to as the “millionaire molecule” because it is the largest antibody in terms of molecular size. It exists mainly as a pentamer structure, consisting of five antibody units linked together by a protein chain called the J chain. This large molecular size gives IgM its unique properties, including efficient agglutination and complement activation.

The other options are incorrect:

• IgA: IgA antibodies are mainly found in mucosal secretions and exist as monomers or dimers. They are not typically referred to as the “millionaire molecule.”
• IgG: IgG antibodies are smaller than IgM and are the most abundant antibody in the bloodstream. While they play crucial roles in immunity, they are not called the “millionaire molecule.”
• IgD: IgD antibodies are found on the surface of mature B-cells and are involved in B-cell activation. They are not referred to as the “millionaire molecule.”

Answer:

Kimishige Ishizaka and his wife Teruko Ishizaka are credited with discovering immunoglobulin E (IgE) in 1966. Their work played a crucial role in understanding the mechanisms of allergic reactions and the role of IgE in these processes.

The other options are incorrect:

• Porter: Rodney R. Porter was a British biochemist who shared the 1972 Nobel Prize in Physiology or Medicine with Gerald M. Edelman for their work on the structure of antibodies. However, he is not associated with the discovery of IgE.
• Richet: Charles Richet was a French physiologist who shared the 1913 Nobel Prize in Physiology or Medicine with Jules Bordet for their work on anaphylaxis. While Richet’s research contributed to the understanding of allergic reactions, he did not discover IgE itself.
• None of these: The combined work of Kimishige and Teruko Ishizaka is widely recognized as the discovery of IgE.

Answer: Both a and c

Antigen-antibody reactions are:

• Reversible: The bonds between antigens and antibodies are non-covalent interactions (like hydrogen bonds, ionic bonds, van der Waals forces). These bonds can form and break under certain conditions. For example, the strength of the interaction can be influenced by factors like temperature, pH, and the concentration of reactants.
• Specific: Antibodies bind only to their specific antigen (or closely related antigens) due to the unique complementary shape (epitope) of the antigen-binding site on the antibody. This specificity allows the immune system to target specific pathogens or foreign molecules.

The other options are incorrect:

Irreversible: Antigen-antibody reactions are not typically irreversible. While some interactions may be long-lasting, they are not permanently fixed and can be disrupted under appropriate conditions.

Answer: Both a and b

Serological reactions are a cornerstone of diagnostic techniques in immunology. They are used for:

• Detection of antigens: By using known antibodies specific to a particular antigen, serological tests can identify the presence of that antigen in a patient’s sample (blood, tissue, etc.). This can be helpful in diagnosing infectious diseases where specific pathogens are targeted.
• Detection of antibodies: Conversely, serological tests can also be designed to detect the presence of antibodies in a patient’s sample.pen_spark

Answer: Immunoelectrophoresis

Immunoelectrophoresis is a method used for the separation and identification of antigens based on their electrophoretic mobility and immunoprecipitation. In this technique, a mixture containing antigens is electrophoresed through a gel, followed by immunodiffusion to detect specific antigens. It allows for the characterization and quantification of antigens present in a sample.

The other options are incorrect:

• Flocculation: Flocculation is a serological reaction in which antigen-antibody complexes form visible clumps or aggregates. It is not a method used for the separation of antigens but rather a qualitative test for the presence of specific antibodies or antigens.
• Agglutination: Agglutination is a serological reaction in which antigen-antibody complexes cause the clumping together of particulate antigens, such as bacteria or red blood cells. It is not a method used for the separation of antigens but rather a qualitative test for the presence of specific antibodies or antigens.

Answer: One antigen/antibody

Counter immunoelectrophoresis (CIE) is a technique designed to detect a specific antigen-antibody complex. It applies an electric current to migrate the antigen and antibody in opposite directions within a gel medium. If a specific antigen-antibody complex is present, a precipitate forms at the zone where they meet in equal concentrations, creating a visible precipitin line.

The other options are incorrect:

• Two antigens/antibody: CIE is not suitable for detecting multiple antigens reacting with a single antibody. It’s specific for one antigen-antibody interaction.
• More than two: Similar to the above, CIE can only identify a single antigen-antibody interaction.
• None of these: CIE is a well-established and reliable method for detecting antigen-antibody complexes.

Answer: Agglutination

Agglutination refers to the clumping of particles, typically cells or bacteria, caused by antibodies specifically binding to antigens on their surfaces. When these antibodies bridge multiple particles, they create a visible lattice structure, resulting in clumping.

The other options are incorrect:

• Precipitation: Precipitation occurs when soluble antigens (dissolved in solution) react with antibodies to form insoluble complexes that precipitate out of the solution.
• Electrophoresis: Electrophoresis is a technique used to separate molecules based on their size and charge in an electric field. It’s not directly involved in antigen-antibody reactions.
• CIE (Counter Immunoelectrophoresis): While CIE also involves antigen-antibody interaction, it’s a specific technique used to detect a single antigen-antibody complex formation in a gel medium. Agglutination is a broader phenomenon observable in various types of antigen-antibody reactions.

Answer: Neutralisation

Neutralization involves rendering a toxin or virus inactive by specific antibodies binding to it, preventing its harmful effects.

The other options are incorrect:

• Precipitation: While precipitation can be used in some antigen-antibody tests, it’s not generally used for detecting toxins or viruses directly.
• Agglutination: Agglutination is typically used for clumping cells or bacteria, not directly applicable to detecting toxins or viruses.

Answer: Exotoxins

Exotoxins are highly antigenic proteins secreted by certain bacteria, often leading to strong immune responses when introduced into the body.

The other options are incorrect:

• Endotoxins: While endotoxins are part of the outer membrane of certain bacteria and can elicit immune responses, they are less antigenic compared to exotoxins.
• Viruses: Viruses can indeed elicit immune responses, but their antigenicity varies depending on factors such as the type of virus and its surface proteins. They are not inherently more antigenic than exotoxins.
• All of these: This option is incorrect because exotoxins are typically more antigenic compared to endotoxins and viruses.

Answer: Both a and b

The secondary functions of complements include aiding in haemolysis (destruction of red blood cells) and enhancing phagocytosis (engulfment and digestion of pathogens by phagocytes).

The other options are incorrect:

• Haemolysis: This is one of the secondary functions of complements, but it is not the only one.
• Phagocytosis: This is also a secondary function of complements, but it is not the only one.
• None of these: This option is incorrect as both haemolysis and phagocytosis are secondary functions of the complement system.

Answer: Humoral immunity

B-cells are the key players in humoral immunity, which involves the production of antibodies that target pathogens in the body fluids (humors).

The other options are incorrect:

• Cell-mediated immunity: This involves T-cells directly attacking infected cells or pathogens, not B-cells and antibody production.
• Active immunity: This refers to the development of immunity by exposure to an antigen and generating your own immune response. B-cells can be involved in both active and humoral immunity, but the question asks specifically about the cell type.
• Passive immunity: This involves receiving antibodies from another source, for example, through vaccination or breast milk. B-cells are not directly involved in passive immunity.

Answer: Non-specific

Innate immunity is the body’s first line of defense and acts in a general way against any foreign invader. It doesn’t distinguish between specific pathogens.

The other options are incorrect:

• Specific: This refers to the adaptive immune system, which develops targeted responses against specific antigens.
• Active: Immunity can be active (developed through exposure) or passive (received from another source). Innate immunity is neither, it’s always present.
• Passive: Similar to active immunity, passive immunity is not a characteristic of innate immunity itself.

Answer: Both a and b

Innate immunity is present at birth and doesn’t require prior exposure. It relies on a combination of:

• Mechanical barriers: Physical structures like skin, mucous membranes, and cilia prevent pathogens from entering the body.
• Chemical barriers: Substances like enzymes, lysozyme in tears, and stomach acid can directly kill or inactivate pathogens.

Answer: All of these

Acquired immunity develops throughout your life in response to exposure to antigens. It can be.

• Natural: Acquired through encountering a pathogen and developing an immune response (e.g., getting sick and recovering).
• Artificial: Acquired through vaccination, where a weakened or inactive form of a pathogen is introduced to stimulate the immune system without causing illness.
• Active: Involves your own immune system actively producing antibodies in response to an antigen.
• Passive: Involves receiving antibodies from another source, like breast milk from a mother or immune globulin injections.

Answer: Both a and b

Acquired immunity develops throughout your life in two main ways:

• Natural means: This occurs when you’re exposed to a pathogen through an infection and your body builds immunity in response.
• Artificial means: This involves vaccination, where a weakened or inactive form of a pathogen is introduced to stimulate the immune system without causing illness.

Answer: Type-I

There are four main types of hypersensitivity reactions. Immediate type hypersensitivity reactions are specifically classified as Type-I.

The other options are incorrect:

• Type-II: This refers to cytotoxic hypersensitivity reactions involving antibody-mediated cell destruction.
• Type-III: This refers to immune complex hypersensitivity reactions involving antigen-antibody complexes causing tissue damage.
• All: Not all types of hypersensitivity reactions are immediate. Type-II and Type-III have different mechanisms and timelines.

Answer: Mast cells

Immediate hypersensitivity reactions involve the release of histamine and other inflammatory mediators from mast cells upon exposure to allergens.

The other options are incorrect:

• T-cells: While T-cells play a role in the immune response, they are not directly involved in the release of mediators during immediate hypersensitivity reactions.
• B-cells: Similar to T-cells, B-cells are involved in antibody production, not the immediate release of inflammatory mediators.
• Macrophages: Macrophages are phagocytic cells that engulf and destroy pathogens. They are not the primary mediators in immediate hypersensitivity reactions.

Answer: All of these

ell-mediated immunity involves the activation of T-cells and other immune cells to directly attack infected cells or pathogens.

• Tuberculin skin test: This test measures cell-mediated immunity against tuberculosis bacteria. If you’ve been exposed, T-cells will react to the injected tuberculin (purified protein derivative), causing a delayed inflammatory response (swelling).
• Contact dermatitis: This reaction, for example, to poison ivy oil, involves T-cells recognizing and targeting skin cells affected by the allergen.
• Granulomatous inflammation: This is a type of chronic inflammation where T-cells orchestrate the formation of compact structures (granulomas) to wall off certain pathogens, like in tuberculosis infections.

Answer: T.B.

The Mantoux test, also called the tuberculin skin test (TST) or Montoux reaction, is used to detect latent tuberculosis infection (LTBI). It checks if your body has ever been exposed to the bacteria that causes tuberculosis (TB).

The other options are incorrect:

• Diphtheria: A different skin test using diphtheria toxin is used to diagnose diphtheria.
• Cholera: Cholera diagnosis typically involves stool tests to identify the specific bacteria causing the infection.
• None of these: The Mantoux test is a well-established tool for identifying potential TB exposure.

Answer: Similar specificity

B-cells are activated by a specific antigen. Once activated, a single B-cell differentiates into plasma cells that all produce identical antibodies with the same antigen-binding site. This ensures a highly targeted immune response against the specific antigen encountered.

The other options are incorrect:

• Different specificities: Antibodies produced by a single B-cell lineage will have the same specificity, targeting the same antigen.
• Similar size: Antibody size can vary slightly depending on the specific antibody class (IgG, IgM, etc.), but all antibodies produced by a single B-cell will be the same size.
• None of these: Both specificity and size are relatively consistent within the antibodies produced by a single B-cell.

Answer: Spleen cell – Myeloma cell

Hybridoma formation in the hybridoma technique involves fusing antibody-producing spleen cells with myeloma cells to create immortalized cells capable of producing monoclonal antibodies.

The other options are incorrect:

• Spleen cell – Spleen cell: This combination would not result in immortalized cells, as spleen cells alone cannot replicate indefinitely like myeloma cells.
• Myeloma cell – Myeloma cell: Fusing two myeloma cells would not produce hybridoma cells capable of producing antibodies with specificities of interest.
• None of these: This option is incorrect because hybridoma formation specifically involves the fusion of spleen cells with myeloma cells to create immortalized cells capable of producing monoclonal antibodies.

Answer: Salk

This is the inactivated poliovirus vaccine (IPV), developed by Jonas Salk. It uses killed (inactivated) poliovirus strains, making it incapable of causing illness but still stimulating the immune system to produce antibodies.

The other options are incorrect:

• Sabin vaccine: This is the oral polio vaccine (OPV), developed by Albert Sabin. It uses weakened (attenuated) live poliovirus strains that can replicate slightly but not enough to cause illness in most people. However, in rare cases, the weakened virus can mutate and regain its ability to cause polio (vaccine-associated paralytic poliomyelitis).
• BCG: This vaccine protects against tuberculosis (TB) and is not related to polio.
• TAB: This vaccine protects against typhoid fever (T), paratyphoid A (A), and paratyphoid B (B) and is not related to polio.

Answer: Antibody producing cells. Memory B cell

The primary immune response is the body’s first encounter with a foreign substance, called an antigen. During this initial response, the immune system takes time to learn about the antigen and develop a specific defense. Here’s why the other options are incorrect.

The other options are incorrect:

• Involves IgG: While IgG is the most abundant antibody class produced during a mature immune response, the primary response may involve a variety of antibody classes, including IgM, as the B cells undergo selection for the most effective ones.
• No lag period: There’s usually a lag period in the primary response as the immune system identifies and tailors its attack against the new antigen.
• Slow and sluggish: The primary response can be slower compared to the secondary response, but it’s still crucial for initiating the immune defense.