Q.1 Which of the following cells is primarily responsible for producing antibodies?
T helper cells
B cells
Macrophages
Natural Killer cells
Explanation - B cells differentiate into plasma cells, which produce antibodies specific to antigens.
Correct answer is: B cells
Q.2 Which class of antibody is mainly found in mucosal surfaces like the gut and respiratory tract?
IgG
IgA
IgM
IgE
Explanation - IgA is the predominant antibody in mucosal areas and secretions, providing local immunity.
Correct answer is: IgA
Q.3 During a primary immune response, the first antibody produced is usually:
IgG
IgA
IgM
IgE
Explanation - IgM is the first antibody produced during initial exposure to an antigen before class switching occurs.
Correct answer is: IgM
Q.4 Which molecule on B cells recognizes specific antigens?
T cell receptor
Major Histocompatibility Complex
B cell receptor
Complement receptor
Explanation - B cell receptors (BCRs) are membrane-bound antibodies on B cells that specifically recognize antigens.
Correct answer is: B cell receptor
Q.5 Which type of immunity is primarily mediated by antibodies?
Cell-mediated immunity
Humoral immunity
Innate immunity
Autophagy
Explanation - Humoral immunity involves B cells and antibody production to neutralize extracellular pathogens.
Correct answer is: Humoral immunity
Q.6 Which cytokine is most important for B cell activation?
IL-2
IL-4
IL-12
IFN-gamma
Explanation - IL-4 is secreted by T helper cells and promotes B cell proliferation and class switching.
Correct answer is: IL-4
Q.7 Affinity maturation in B cells occurs in:
Bone marrow
Thymus
Germinal centers of lymph nodes
Spleen red pulp
Explanation - Affinity maturation occurs in germinal centers where B cells undergo somatic hypermutation to produce high-affinity antibodies.
Correct answer is: Germinal centers of lymph nodes
Q.8 Which antibody class is involved in allergic reactions?
IgG
IgA
IgE
IgM
Explanation - IgE binds to allergens and triggers mast cells and basophils to release histamine, causing allergic symptoms.
Correct answer is: IgE
Q.9 The process by which B cells switch from producing one class of antibody to another is called:
Somatic hypermutation
Class switching
Clonal selection
Opsonization
Explanation - Class switching allows B cells to produce different antibody isotypes (e.g., IgM to IgG) without changing antigen specificity.
Correct answer is: Class switching
Q.10 Which of the following is NOT a function of antibodies?
Neutralization of toxins
Activation of complement
Directly killing infected cells
Opsonization
Explanation - Antibodies neutralize pathogens and enhance phagocytosis but do not directly kill cells; that is mediated by cytotoxic T cells.
Correct answer is: Directly killing infected cells
Q.11 Plasma cells are derived from:
T cells
B cells
Macrophages
Dendritic cells
Explanation - Upon activation by antigen and helper T cells, B cells differentiate into plasma cells, which secrete large amounts of antibodies.
Correct answer is: B cells
Q.12 Which of the following antibodies is the most abundant in serum?
IgM
IgA
IgG
IgE
Explanation - IgG is the most abundant antibody in blood and extracellular fluid, providing long-term immunity.
Correct answer is: IgG
Q.13 Opsonization is the process by which:
Antibodies neutralize toxins
Pathogens are marked for phagocytosis
Complement destroys cells directly
T cells kill infected cells
Explanation - Antibodies coat pathogens, enhancing their recognition and ingestion by phagocytes.
Correct answer is: Pathogens are marked for phagocytosis
Q.14 Which immunoglobulin can cross the placenta to provide passive immunity to the fetus?
IgM
IgG
IgA
IgE
Explanation - IgG antibodies are transported across the placenta, providing the newborn with temporary immunity.
Correct answer is: IgG
Q.15 Memory B cells are important because they:
Produce antibodies immediately upon first exposure
Remember antigens for faster response upon re-exposure
Activate T cells
Kill infected cells directly
Explanation - Memory B cells persist after primary infection and provide rapid, robust antibody responses upon subsequent exposures.
Correct answer is: Remember antigens for faster response upon re-exposure
Q.16 Which part of the antibody binds to the antigen?
Fc region
Variable region
Constant region
Hinge region
Explanation - The variable region of the antibody binds specifically to the antigen, determining its specificity.
Correct answer is: Variable region
Q.17 Which of the following antibodies is primarily responsible for early defense against blood-borne infections?
IgG
IgA
IgM
IgE
Explanation - IgM is the first antibody produced and is effective in controlling infections in the early stages.
Correct answer is: IgM
Q.18 Which type of hypersensitivity reaction is mainly mediated by IgE?
Type I
Type II
Type III
Type IV
Explanation - Type I hypersensitivity is immediate and involves IgE binding to allergens and triggering mast cell degranulation.
Correct answer is: Type I
Q.19 Which organ is the primary site of B cell maturation in humans?
Thymus
Bone marrow
Spleen
Lymph nodes
Explanation - B cells mature in the bone marrow where they undergo selection to prevent self-reactivity.
Correct answer is: Bone marrow
Q.20 Which of the following best describes the role of helper T cells in humoral immunity?
Directly produce antibodies
Activate B cells and promote antibody production
Phagocytose pathogens
Secrete complement proteins
Explanation - Helper T cells secrete cytokines that stimulate B cells to proliferate and differentiate into antibody-secreting plasma cells.
Correct answer is: Activate B cells and promote antibody production
Q.21 Which antibody class is predominantly found in tears, saliva, and breast milk?
IgG
IgA
IgM
IgE
Explanation - IgA provides mucosal immunity and is secreted in various bodily fluids to prevent pathogen entry.
Correct answer is: IgA
Q.22 Somatic hypermutation in B cells results in:
Production of IgE
Increased antibody affinity
Class switching
Memory T cell formation
Explanation - Somatic hypermutation introduces point mutations in the variable region of BCR genes, leading to higher affinity antibodies.
Correct answer is: Increased antibody affinity
Q.23 Which of the following is a primary lymphoid organ involved in humoral immunity?
Lymph node
Bone marrow
Spleen
Tonsils
Explanation - Primary lymphoid organs, like bone marrow, are sites where B cells develop and mature before entering peripheral tissues.
Correct answer is: Bone marrow
Q.24 Which antibody class is mainly involved in defense against parasitic worms?
IgG
IgA
IgM
IgE
Explanation - IgE binds to parasites and activates eosinophils and mast cells to mediate the immune response.
Correct answer is: IgE