A 50-year-old man with metastatic melanoma is started on immunotherapy with ipilimumab. This monoclonal antibody blocks CTLA-4, thereby enhancing T-cell activation. Which normal immune function does CTLA-4 normally serve?

• A Delivering an inhibitory signal to activated T cells ✓
• B Promoting T-cell proliferation in lymph nodes
• C Facilitating antigen presentation by dendritic cells
• D Inducing apoptosis of tumor cells via Fas-FasL interaction

Explanation

CTLA-4 is an immune checkpoint receptor expressed on T cells that delivers an inhibitory signal upon binding to A7 on antigen-presenting cells, thereby downregulating T-cell responses. Ipilimumab blocks this inhibitory signal, unleashing anti-tumor immunity. CTLA-4 does not promote proliferation, facilitate antigen presentation, or directly induce tumor apoptosis via Fas-FasL.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.