1. What interaction marks the initiation of adaptive immunity?
A. Cytokine release
B. PAMP-PRR interaction
C. Three-signal hypothesis
D. Complement activation
C. Three-signal hypothesis
2. Which molecules are involved in Signal 1 of T cell activation?
A. CD80/CD86 and CD28
B. MHC II/Antigen and TCR
C. Cytokine and cytokine receptor
D. CD40 and CD40L
B. MHC II/Antigen and TCR
3. What is the purpose of Signal 2?
A. Initiates clonal expansion
B. Determines T cell fate (activation or anergy)
C. Presents antigen to the T cell
D. Triggers macrophage activation
B. Determines T cell fate (activation or anergy)
4. Which interaction provides Signal 2?
A. MHC I and CD8
B. MHC II and CD4
C. CD80/CD86 (B7) and CD28
D. Cytokine and cytokine receptor
C. CD80/CD86 (B7) and CD28
5. A T cell receives Signal 1 but no Signal 2. What happens?
A. Apoptosis
B. Anergy
C. Activation
D. Proliferation
B. Anergy
6. What molecule determines the type of helper T cell produced?
A. The cytokine environment
B. MHC expression
C. ITAM activation
D. CTLA-4 expression
A. The cytokine environment
7. What is the function of pSMAC?
A. Signal transduction
B. Adhesion
C. Cytokine release
D. Transcription
B. Adhesion
8. What is the function of CD3?
A. Antigen presentation
B. Signal transduction for TCR
C. Binds MHC molecules
D. Acts as a co-stimulatory receptor
B. Signal transduction for TCR
9. Which of the following binds to MHC class I?
A. CD4
B. CD8
C. CD28
D. CD40
B. CD8
10. Which transcription factors are activated through CD3 signaling?
A. FOXP3 ,STAT3
B. NFAT, NF-κB, AP-1
C. IL-2, IL-4 ,IL-10
D. MAPK ,ICAM-1
B. NFAT, NF-κB, AP-1
11. What is the function of CTLA-4? A. Co-stimulatory receptor
B. Co-inhibitory receptor
C. Cytokine receptor
D. Adhesion molecule
B. Co-inhibitory receptor
12. Which of the following statements about checkpoint inhibitors is true?
A. They block CTLA-4 to keep T cells active
B. They activate Tregs
C. They prevent cytokine signaling
D. They enhance peripheral tolerance
A. They block CTLA-4 to keep T cells active
13. Which cytokine drives autocrine T cell proliferation?
A. IL-4
B. IL-2
C. IL-10
D. IFN-γ
B. IL-2
14. Which helper T cell subtype combats intracellular pathogens?
A. TH1
B. TH2
C. TH17
D. Treg
A. TH1
15. Which helper T cell secretes IL-17 and fights extracellular bacteria/fungi?
A. TH1
B. TH2
C. TH17
D. Treg
C. TH17
16. TH1
function: Macrophage activation
cytokines: IFN-γ ,TNF
role in disease: Tissue inflammation
17. TH2
function: Allergy
cytokines: IL-4, IL-5, IL-13
role in disease: Allergy
18. TH17
function: Macrophage activation
cytokines: IL-17, IL-22
role in disease: Autoimmunity
19. Treg
function: Suppresses other T cells
cytokines: IL-10, TGF-β
role in disease: Antitumor inhibition
20. TFH
function:Germinal center regulation
cytokines: IL-4, IL-21
role in disease: Lymphoid tissue
21. Describe the three-signal hypothesis in T cell activation.
Signal 1 (MHC–TCR), Signal 2 (CD80/86–CD28), Signal 3 (Cytokine–receptor).
22. Explain the difference between paracrine and autocrine signaling in Signal 3.
Paracrine = cytokine acts on nearby cells; Autocrine = IL-2 acts on same T cell to proliferate.
23. What is the function of LCK and ITAMs in TCR signaling?
LCK phosphorylates ITAMs on CD3 → starts TCR signaling cascade.
24. List the three outcomes of CD3 signaling.
Cell survival, proliferation, differentiation.
25. What are central and peripheral Tregs, and how do they differ?
Central Tregs = develop in thymus; Peripheral Tregs = induced in tissues after activation.
26. How do Tregs suppress the immune response?
Use IL-10/TGF-β, IL-2 competition, APC inhibition, or cytotoxicity.
27. What is reciprocal inhibition, and why is it important for T cell polarization?
Opposing pathways inhibit each other; ensures only one helper T subset dominates.
28. Describe how a TH1 cell activates macrophages at the site of infection.
TH1 binds MHC II on macrophage; IFN-γ + CD40L activate macrophage to increase lysosome fusion and NO.