Answer: 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.
- 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.
The Plasmodium parasite needs both hosts: the female Anopheles mosquito injects sporozoites while biting (infecting the human liver and RBCs, causing the malaria fever cycle), then picks up gametocytes from an infected person's blood, completing the parasite's sexual stage inside the mosquito.
Concept context
Pathogens, infectious diseases, non-infectious diseases, drugs, cancer, and public health. High NEET importance.