Rituximab is a monoclonal antibody used in CD20-positive B-cell lymphomas. Its mechanisms of B-cell killing include all EXCEPT:
- A Blocking CD20's ion channel function, depleting intracellular calcium stores required for B-cell survival ✓
- B Complement-dependent cytotoxicity (CDC)
- C Antibody-dependent cell-mediated cytotoxicity (ADCC)
- D Direct induction of apoptosis via CD20 crosslinking
Correct answer: A. Blocking CD20's ion channel function, depleting intracellular calcium stores required for B-cell survival
Explanation
Rituximab kills CD20+ B-cells via three well-established mechanisms: CDC (Fc region binds C1q, activating complement cascade), ADCC (Fc region binds FcγRIII on NK cells/macrophages), and direct apoptosis induction by crosslinking CD20. CD20 is a calcium-permeable ion channel and rituximab binding does affect intracellular calcium, but 'depleting intracellular calcium stores' is not recognized as a distinct primary killing mechanism — it is incidental to CD20 crosslinking-mediated apoptosis. The three accepted mechanisms are CDC, ADCC, and direct apoptosis.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.