Q.1 Which cells are primarily responsible for antibody production in adaptive immunity?
T helper cells
Plasma cells
Cytotoxic T cells
Macrophages
Explanation - Plasma cells, derived from B lymphocytes, are the main producers of antibodies in adaptive immunity.
Correct answer is: Plasma cells
Q.2 Which type of T cell directly kills virus-infected cells?
T helper cells
Cytotoxic T cells
Regulatory T cells
Memory B cells
Explanation - Cytotoxic T cells (CD8+) recognize and destroy virus-infected or abnormal cells.
Correct answer is: Cytotoxic T cells
Q.3 Which molecule presents antigen to T cells in adaptive immunity?
Immunoglobulin
MHC
Complement protein
Cytokine
Explanation - Major Histocompatibility Complex (MHC) molecules present antigens to T cells for recognition.
Correct answer is: MHC
Q.4 What type of immunity develops after recovering from an infection?
Passive natural immunity
Active natural immunity
Passive artificial immunity
Active artificial immunity
Explanation - Exposure to a pathogen during infection leads to active natural immunity via memory cell formation.
Correct answer is: Active natural immunity
Q.5 Which immunoglobulin is the first to appear during a primary immune response?
IgA
IgE
IgM
IgG
Explanation - IgM is the first antibody produced during primary exposure to an antigen.
Correct answer is: IgM
Q.6 Which T cells help activate B cells?
Cytotoxic T cells
T helper cells
Regulatory T cells
NK cells
Explanation - T helper cells (CD4+) secrete cytokines that activate B cells for antibody production.
Correct answer is: T helper cells
Q.7 Which is a feature unique to adaptive immunity?
Phagocytosis
Specificity
Inflammation
Fever
Explanation - Adaptive immunity is characterized by antigen-specific recognition and memory.
Correct answer is: Specificity
Q.8 Which type of cell is responsible for long-term immune memory?
Macrophages
Memory lymphocytes
Neutrophils
NK cells
Explanation - Memory B and T cells provide long-term protection against previously encountered antigens.
Correct answer is: Memory lymphocytes
Q.9 Vaccination is an example of which type of immunity?
Passive artificial immunity
Active artificial immunity
Passive natural immunity
Active natural immunity
Explanation - Vaccination introduces antigens artificially, leading to active immune response and memory formation.
Correct answer is: Active artificial immunity
Q.10 Which antibody can cross the placenta to protect the fetus?
IgA
IgM
IgE
IgG
Explanation - IgG is the only immunoglobulin that crosses the placenta to provide passive immunity to the fetus.
Correct answer is: IgG
Q.11 Which cytokine is crucial for T helper cell differentiation?
IL-2
IL-4
IL-12
TNF-alpha
Explanation - IL-12 promotes differentiation of naïve T helper cells into Th1 subtype, important in cell-mediated immunity.
Correct answer is: IL-12
Q.12 Which immunoglobulin is most abundant in mucosal secretions?
IgE
IgG
IgA
IgM
Explanation - IgA is the dominant antibody in mucosal surfaces, providing protection against pathogens at entry sites.
Correct answer is: IgA
Q.13 Which process generates antibody diversity?
Somatic hypermutation
Complement activation
Opsonization
Phagocytosis
Explanation - Somatic hypermutation introduces mutations in antibody genes, increasing diversity and affinity.
Correct answer is: Somatic hypermutation
Q.14 Which co-receptor is expressed on helper T cells?
CD8
CD4
CD19
CD56
Explanation - Helper T cells express CD4, which interacts with MHC class II molecules.
Correct answer is: CD4
Q.15 Which cells suppress overactive immune responses?
Cytotoxic T cells
Regulatory T cells
NK cells
B cells
Explanation - Regulatory T cells (Tregs) help maintain immune tolerance and prevent autoimmunity.
Correct answer is: Regulatory T cells
Q.16 Which region of an antibody binds to antigens?
Fc region
Fab region
Constant region
Light chain hinge
Explanation - The Fab region contains variable domains responsible for antigen recognition.
Correct answer is: Fab region
Q.17 Which MHC class presents antigens to cytotoxic T cells?
MHC I
MHC II
MHC III
Both I and II
Explanation - MHC class I presents endogenous antigens to CD8+ cytotoxic T cells.
Correct answer is: MHC I
Q.18 Which immunoglobulin is associated with allergic reactions?
IgG
IgA
IgE
IgM
Explanation - IgE binds to mast cells and basophils, playing a central role in allergic reactions.
Correct answer is: IgE
Q.19 Which cells act as professional antigen-presenting cells?
Neutrophils
Dendritic cells
Eosinophils
Basophils
Explanation - Dendritic cells are the most efficient antigen-presenting cells, initiating T cell responses.
Correct answer is: Dendritic cells
Q.20 Which immune cells undergo positive and negative selection in the thymus?
B cells
Macrophages
T cells
NK cells
Explanation - T cells mature in the thymus, where selection ensures self-tolerance and proper antigen recognition.
Correct answer is: T cells
Q.21 Which process enables cytotoxic T cells to induce apoptosis?
Perforin-granzyme pathway
Phagocytosis
Opsonization
Neutralization
Explanation - Cytotoxic T cells release perforin and granzymes to induce apoptosis in target cells.
Correct answer is: Perforin-granzyme pathway
Q.22 Which antibody is found in breast milk providing passive immunity to infants?
IgM
IgG
IgA
IgE
Explanation - Secretory IgA in breast milk provides mucosal protection to infants.
Correct answer is: IgA
Q.23 Which immune response is faster: primary or secondary?
Primary response
Secondary response
Both equal
Neither
Explanation - Secondary immune response is faster and stronger due to memory cell activation.
Correct answer is: Secondary response
Q.24 Which enzyme is crucial for V(D)J recombination in adaptive immunity?
DNA polymerase
RAG1/2
Reverse transcriptase
Topoisomerase
Explanation - RAG1/2 enzymes mediate V(D)J recombination, essential for antigen receptor diversity.
Correct answer is: RAG1/2
Q.25 Which immunoglobulin is pentameric in its secreted form?
IgG
IgM
IgE
IgA
Explanation - Secreted IgM forms a pentamer, making it effective in complement activation.
Correct answer is: IgM