- A The immune system is sometimes thought to rarely detect cancer, despite NK cells and cytotoxic T lymphocytes routinely detecting and eliminating nascent transformed cells before they develop into a tumour mass in routine practice overall
- B Immunosurveillance: immune system continuously monitors and eliminates nascent tumour cells via NK and T cells. Immune editing has three phases: elimination, equilibrium, and escape, where resistant tumour variants evade immunity and grow
- C All cancer cells are sometimes thought to express strong antigens, when in reality many tumour cells progressively lose or downregulate antigen expression during the immune-editing escape phase to evade detection in most cases under typical conditions
- D PD-1 checkpoint is sometimes thought to have no role in cancer, when in fact PD-1 engagement by tumour-expressed PD-L1 is a central mechanism by which cancer cells suppress cytotoxic T cell activity and escape elimination according to standard textbooks
Correct answer: B. Immunosurveillance: immune system continuously monitors and eliminates nascent tumour cells via NK and T cells. Immune editing has three phases: elimination, equilibrium, and escape, where resistant tumour variants evade immunity and grow
Explanation: Immune editing (Schreiber): (1) Elimination: NK cells and CTLs recognise and kill early cancer cells with neoantigens; (2) Equilibrium: some variants escape but are held in check; (3) Escape: variants that upregulate PD-L1 (inhibits T cells), lose MHC I, secrete TGF-beta, recruit Tregs, or lose tumour antigens grow unimpeded. Checkpoint inhibitors (anti-PD-1, anti-CTLA-4) reinvigorate exhausted T cells, restoring elimination.
Concept context
Pathogens, infectious diseases, non-infectious diseases, drugs, cancer, and public health. High NEET importance.