Q.1 Which type of T cell is primarily responsible for killing virus-infected cells?
Helper T cells (CD4+)
Cytotoxic T cells (CD8+)
Regulatory T cells
B cells
Explanation - Cytotoxic T cells (CD8+) recognize and directly kill virus-infected cells by inducing apoptosis.
Correct answer is: Cytotoxic T cells (CD8+)
Q.2 Which molecule on antigen-presenting cells presents antigen to CD4+ T cells?
MHC Class I
MHC Class II
TCR
CD8
Explanation - MHC Class II molecules present processed antigens to CD4+ helper T cells, initiating their activation.
Correct answer is: MHC Class II
Q.3 Which cytokine is crucial for the activation of macrophages by T helper cells?
IL-2
IFN-γ
IL-4
TNF-α
Explanation - Interferon-gamma (IFN-γ) secreted by Th1 cells activates macrophages to enhance their microbicidal activity.
Correct answer is: IFN-γ
Q.4 Delayed-type hypersensitivity is mainly mediated by:
B cells
CD8+ T cells
CD4+ T cells (Th1)
Neutrophils
Explanation - Th1 cells mediate delayed-type hypersensitivity by releasing cytokines that recruit and activate macrophages at the site of antigen exposure.
Correct answer is: CD4+ T cells (Th1)
Q.5 Which of the following is NOT a function of cytotoxic T cells?
Killing infected cells
Releasing perforin
Secreting antibodies
Inducing apoptosis
Explanation - Cytotoxic T cells kill infected or abnormal cells but do not secrete antibodies; antibody production is the function of B cells.
Correct answer is: Secreting antibodies
Q.6 Which receptor on T cells recognizes antigen presented by MHC molecules?
BCR
TCR
CD28
Fc receptor
Explanation - The T cell receptor (TCR) specifically recognizes antigens presented by MHC molecules on antigen-presenting cells.
Correct answer is: TCR
Q.7 Activation of naive T cells requires:
Antigen recognition only
Co-stimulatory signals only
Antigen recognition and co-stimulation
Cytokine signaling only
Explanation - Naive T cells require both TCR recognition of antigen-MHC complex and co-stimulatory signals (e.g., CD28 binding B7) for full activation.
Correct answer is: Antigen recognition and co-stimulation
Q.8 Which subset of T cells helps B cells in antibody production?
Th1
Th2
Th17
Cytotoxic T cells
Explanation - Th2 cells secrete cytokines like IL-4 and IL-5 that help B cells proliferate and differentiate into plasma cells producing antibodies.
Correct answer is: Th2
Q.9 Granzyme and perforin are associated with:
Helper T cells
Cytotoxic T cells
Regulatory T cells
Macrophages
Explanation - Cytotoxic T cells use perforin to form pores in target cells and granzymes to induce apoptosis.
Correct answer is: Cytotoxic T cells
Q.10 Which of the following cells can present antigen via MHC Class I?
All nucleated cells
Red blood cells only
B cells only
Macrophages only
Explanation - All nucleated cells express MHC Class I, allowing cytotoxic T cells to recognize infected or abnormal cells.
Correct answer is: All nucleated cells
Q.11 Th17 cells are mainly involved in:
Autoimmunity and inflammation
Viral clearance
Allergic responses
B cell help
Explanation - Th17 cells secrete IL-17 and are implicated in inflammation and autoimmune disease pathogenesis.
Correct answer is: Autoimmunity and inflammation
Q.12 Which transcription factor is crucial for cytotoxic T cell differentiation?
GATA3
T-bet
RORγt
Foxp3
Explanation - T-bet directs the differentiation of CD8+ cytotoxic T cells and Th1 cells by regulating gene expression.
Correct answer is: T-bet
Q.13 Which molecule is a co-inhibitory receptor on T cells?
CD28
CTLA-4
CD3
CD8
Explanation - CTLA-4 is an inhibitory receptor that downregulates T cell activation to maintain immune tolerance.
Correct answer is: CTLA-4
Q.14 The main function of regulatory T cells (Tregs) is to:
Enhance cytotoxicity
Suppress immune responses
Activate B cells
Promote inflammation
Explanation - Tregs maintain immune homeostasis by suppressing excessive immune responses and preventing autoimmunity.
Correct answer is: Suppress immune responses
Q.15 Which cytokine is primarily responsible for T cell proliferation after activation?
IL-2
IL-4
IL-10
IFN-γ
Explanation - IL-2 is secreted by activated T cells and drives clonal expansion of T cells.
Correct answer is: IL-2
Q.16 Which pathway is mainly responsible for antigen processing for MHC Class I presentation?
Endocytic pathway
Cytosolic pathway
Exocytotic pathway
Phagocytic pathway
Explanation - Endogenous antigens from the cytosol are processed by the proteasome and presented on MHC Class I molecules.
Correct answer is: Cytosolic pathway
Q.17 Which type of hypersensitivity involves cell-mediated immunity without antibodies?
Type I
Type II
Type III
Type IV
Explanation - Type IV hypersensitivity is mediated by T cells and macrophages rather than antibodies, as seen in contact dermatitis.
Correct answer is: Type IV
Q.18 Which T cell subset produces IL-4, IL-5, and IL-13?
Th1
Th2
Th17
Treg
Explanation - Th2 cells produce cytokines that promote humoral immunity and are involved in allergic responses.
Correct answer is: Th2
Q.19 Which molecule stabilizes the interaction between TCR and MHC on T cells?
CD28
CD4/CD8
CD3
CTLA-4
Explanation - CD4 binds MHC Class II and CD8 binds MHC Class I, stabilizing TCR-MHC interactions for efficient signaling.
Correct answer is: CD4/CD8
Q.20 Which T cell subset is primarily involved in granuloma formation?
Th1
Th2
Th17
Treg
Explanation - Th1 cells release IFN-γ to activate macrophages, which aggregate to form granulomas in chronic infections.
Correct answer is: Th1
Q.21 Which immune checkpoint is targeted by cancer immunotherapy to enhance T cell response?
CD28
PD-1
CD3
MHC I
Explanation - Blocking PD-1 or its ligand PD-L1 releases T cells from inhibition, allowing enhanced anti-tumor activity.
Correct answer is: PD-1
Q.22 Which enzyme degrades proteins into peptides for MHC Class II presentation?
Proteasome
Cathepsin
DNA polymerase
Kinase
Explanation - Cathepsins in endosomes/lysosomes degrade proteins into peptides for loading onto MHC Class II molecules.
Correct answer is: Cathepsin
Q.23 Which chemokine primarily recruits T cells to infection sites?
CCL2
CXCL10
IL-8
IL-10
Explanation - CXCL10 attracts activated T cells to sites of infection or inflammation.
Correct answer is: CXCL10
Q.24 Which of the following best describes the role of perforin?
Stimulates antibody production
Forms pores in target cell membrane
Inhibits T cell activation
Degrades viral DNA
Explanation - Perforin released by cytotoxic T cells forms pores in target cell membranes, allowing granzymes to enter and induce apoptosis.
Correct answer is: Forms pores in target cell membrane
Q.25 Cross-presentation allows:
MHC Class I presentation of extracellular antigens
MHC Class II presentation of intracellular antigens
T cell-independent activation of B cells
Antibody secretion by T cells
Explanation - Certain dendritic cells can present extracellular antigens on MHC Class I to activate CD8+ T cells, a process called cross-presentation.
Correct answer is: MHC Class I presentation of extracellular antigens