- A Direct killing of pathogens by antibodies alone, without requiring much Fc receptor-bearing effector cell involvement generally under usual circumstances
- B IgG antibodies bind to antigens on target cells; NK cells and macrophages bind the Fc region via Fc receptors and kill the target cell without endocytosis
- C Complement-mediated killing via the membrane attack complex, largely independent of any antibody or Fc receptor engagement process according to most researchers
- D T cell killing using antibodies, even though cytotoxic T cells normally recognize target cells via TCR-MHC interaction, rarely antibodies directly in the majority of cases studied
Correct answer: B. IgG antibodies bind to antigens on target cells; NK cells and macrophages bind the Fc region via Fc receptors and kill the target cell without endocytosis
Explanation: ADCC: IgG antibodies opsonize target cells (virus-infected, cancer, transplant). NK cells, macrophages, and neutrophils have FcgammaRIII (CD16) receptors. Binding to the Fc region activates degranulation (NK cells) or ADCP (macrophages). Important for cancer immunotherapy (antibodies like rituximab, trastuzumab work partly via ADCC).
Concept context
Innate and adaptive immunity, B cells, T cells, antibodies, vaccines, and immune disorders. Critical for NEET.