Q.48 Which of the following statement(s) is/are CORRECT for antigen activated effector T cells?
P. CD4+ cells make contact with macrophages and stimulate their microbicidal activity
Q. CD4 + cells make contact with B cells and stimulate them to differentiate into plasma cells
R. CD8 + cells make contact with B cells and stimulate them to differentiate into plasma cells
S. CD8 + cells make contact with virus infected cells and kill them
(A) Q only (B) Q and S only (C) P, Q and S only (D) P, Q, R and S
Antigen-Activated Effector T Cells Functions: CD4+ CD8+ Interactions MCQ Solution
CD4+ helper T cells activate macrophages and B cells while CD8+ cytotoxic T cells kill infected cells directly. The correct statements identify these canonical effector functions without CD8-B cell differentiation role.
Option Analysis
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P. CD4+ cells make contact with macrophages and stimulate their microbicidal activity: CORRECT. Th1 cells secrete IFN-γ activating macrophage phagocytosis, NO/iNOS production, and phagolysosome fusion against intracellular pathogens.
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Q. CD4+ cells make contact with B cells and stimulate them to differentiate into plasma cells: CORRECT. Tfh cells via CD40L-CD40, IL-4/IL-21 induce germinal center B cell proliferation, class switching, and plasma cell differentiation.
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R. CD8+ cells make contact with B cells and stimulate them to differentiate into plasma cells: INCORRECT. CD8+ CTLs target MHC-I antigen-presenting cells (infected cells, not B cells for help); B cell activation requires MHC-II/CD4+ interaction.
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S. CD8+ cells make contact with virus infected cells and kill them: CORRECT. CTLs recognize viral peptides on MHC-I via TCR, release perforin/granzyme B, Fas-FasL inducing apoptosis.
Correct Answer
(C) P, Q and S only. Excludes R as CD8+ T cells lack cognate B cell helper function.
Antigen activated effector T cells functions distinguish CD4+ helper (Th1/Tfh) from CD8+ cytotoxic roles in adaptive immunity. P, Q, S correctly describe canonical interactions: Th1→macrophage activation (tuberculoid leprosy protection), Tfh→B cell affinity maturation (1000x Ab increase), CTL→viral clearance (influenza control). R fails as CD8+ recognize MHC-I not MHC-II on B cells.
T Cell Effector Functions Visualized
| Statement | Cell Type | Target | Mechanism | Outcome |
|---|---|---|---|---|
| P ✓ | CD4+ Th1 | Macrophages | IFN-γ, TNF-α | Microbicidal NO, ROS |
| Q ✓ | CD4+ Tfh | B cells | CD40L, IL-21 | Plasma cells, GC |
| R ✗ | CD8+ CTL | B cells | None (MHC-I vs II) | No B help |
| S ✓ | CD8+ CTL | Infected cells | Perforin/granzyme | Apoptosis |
Exam Strategy & Traps
Key distinction: CD4+ = MHC-II helper (macrophages, B cells, DCs); CD8+ = MHC-I killer (any nucleated cell). Mnemonic: “4 helps 2 (MHC-II), 8 kills 1 (MHC-I)”. R traps confuse indirect CD8 licensing by CD4 help with direct B cell contact.
Clinical correlations:
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HIV CD4+ loss → poor macrophage/B cell responses → opportunistic infections
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CD8+ dysfunction → viral persistence (chronic HCV)
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Cancer immunotherapy targets PD-1/TIGIT on exhausted CTLs
Biotech applications: CAR-T therapy engineers CD8+ chassis with CD4+ cytokines (IL-2/15) for enhanced persistence; bispecific T cell engagers mimic natural synapse formation. Option C perfect for GATE/CSIR NET pattern recognition.
