Pembrolizumab and nivolumab are immune checkpoint inhibitors used in cancer immunotherapy. The immune pathway they target is:
- A They block the PD-1 receptor on T lymphocytes, preventing PD-L1/PD-L2-mediated T-cell exhaustion and restoring anti-tumour immunity ✓
- B They block the CTLA-4 receptor on regulatory T cells, reducing T-cell suppression
- C They activate TLR-9 signalling on dendritic cells, enhancing tumour antigen presentation
- D They inhibit the LAG-3 checkpoint, preventing MHC II-mediated T-cell inhibition
Correct answer: A. They block the PD-1 receptor on T lymphocytes, preventing PD-L1/PD-L2-mediated T-cell exhaustion and restoring anti-tumour immunity
Explanation
Pembrolizumab and nivolumab are anti-PD-1 monoclonal antibodies. PD-1 (programmed death 1) is an inhibitory receptor on activated T cells; its ligation by tumour-expressed PD-L1 or PD-L2 signals T-cell exhaustion and immune evasion. Blocking PD-1 prevents this inhibitory signalling, restoring T-cell proliferation, cytokine production, and cytotoxic killing of tumour cells. CTLA-4 blockade is the mechanism of ipilimumab (active at the priming/lymph node phase), while PD-1 blockade acts at the tumour microenvironment effector phase.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.