- A By releasing antibodies synthesized and secreted directly into the bloodstream by activated plasma cells located nearby in routine practice overall in most cases
- B By releasing perforin (pore-forming protein) and granzymes (serine proteases) that trigger apoptosis in target cells, plus FasL binding Fas to trigger apoptosis
- C By phagocytosis of target cells, engulfing the entire infected cell whole rather than triggering its controlled apoptosis process under typical conditions
- D By producing toxic cytokines mainly, without much direct involvement of perforin, granzymes, or Fas-FasL signaling generally according to standard textbooks
Correct answer: B. By releasing perforin (pore-forming protein) and granzymes (serine proteases) that trigger apoptosis in target cells, plus FasL binding Fas to trigger apoptosis
Explanation: CTLs kill via two main mechanisms: (1) Granule exocytosis: perforin polymerizes in target membrane forming pores; granzymes enter through pores and activate caspases/apoptosis. (2) Death receptor pathway: FasL on CTL binds Fas on target cell, activating caspase cascade and apoptosis. Both result in controlled death of infected cells.
Concept context
Innate and adaptive immunity, B cells, T cells, antibodies, vaccines, and immune disorders. Critical for NEET.