Abatacept Mechanism — SCE Rheumatology MCQ
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Correct answer: B — Binding to CD80 and CD86 to inhibit T-cell co-stimulation
Abatacept is a fusion protein comprising the extracellular domain of CTLA-4 linked to a modified human IgG1 Fc region. It binds CD80 and CD86 on antigen-presenting cells, preventing their interaction with CD28 on T lymphocytes. This blocks the second, co-stimulatory signal required for full T-cell activation. TNF-alpha neutralisation describes TNF inhibitors, whereas CD20 binding and B-cell depletion describe rituximab. IL-6 receptor blockade is the mechanism of agents such as tocilizumab and sarilumab. JAK inhibitors act intracellularly by inhibiting Janus kinase-mediated cytokine signalling rather than by blocking cell-surface co-stimulation.
Reference: electronic Medicines Compendium. ORENCIA 125 mg solution for injection in pre-filled pen: Summary of Product Characteristics, section 5.1, Mechanism of action. Current SmPC accessed 26 August 2026. https://www.medicines.org.uk/emc/product/6815/smpc