A 58-year-old man with relapsed CD20-positive follicular lymphoma receives his first infusion of rituximab and develops fever, rigors, hypotension and bronchospasm within 30 minutes. This reaction is attributed to which mechanism?

• A IgE-mediated type I hypersensitivity to murine protein
• B Antibody-dependent cellular cytotoxicity mediated by NK cells
• C Complement activation and cytokine release from tumour cell lysis ✓
• D Direct apoptosis of B cells via CD20 cross-linking

Explanation

The infusion reaction during the first rituximab dose reflects complement activation (B3a, B5a anaphylatoxins) and release of TNF-alpha and IL-6 from lysed tumour cells. It is a pharmacodynamic effect of tumour burden, not true IgE allergy, so it is managed by slowing or stopping the infusion, antihistamines and steroids. The reaction is rare after subsequent doses because circulating CD20-positive C cells are already depleted. Premedication reduces its incidence.

Reference: Katzung Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.