Blinatumomab, approved for relapsed/refractory B-cell acute lymphoblastic leukaemia, differs from conventional monoclonal antibodies because its antitumour action depends on:
- A Complement-mediated lysis of CD19-positive blasts
- B Simultaneous binding of CD19 on leukaemic cells and CD3 on T cells, forming a cytolytic synapse ✓
- C Blockade of the PD-1 receptor on exhausted cytotoxic T lymphocytes
- D Antibody-dependent cellular cytotoxicity through Fc-gamma receptors on NK cells
Correct answer: B. Simultaneous binding of CD19 on leukaemic cells and CD3 on T cells, forming a cytolytic synapse
Explanation
Blinatumomab is a bispecific T-cell engager (BiTE): two single-chain antibody fragments joined by a short linker, one binding CD19 on B-lineage blasts and the other binding CD3 on T cells. By physically bridging them it forces formation of an immune synapse and polyclonal T-cell activation independent of MHC presentation. Because the linker is too short for Fc functions and there is no Fc region, complement lysis and ADCC cannot occur, eliminating options A and D, and it has no checkpoint-blocking activity.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.