Which drug is a selective costimulation T cell modifier?

• A. Abatacept
• B. Anakinra
• C. Rituximab
• D. Tocilizumab

Answer: (A)

Abatacept works by blocking the second, or costimulatory, signal required for full T cell activation. It’s a fusion protein that combines CTLA-4 with an IgG1 Fc, and it binds CD80/CD86 on antigen-presenting cells. By occupying these costimulatory ligands, it prevents CD28 on T cells from delivering the essential costimulatory signal. Without this signal, even if the T cell recognizes its antigen, it won’t fully activate, proliferate, or produce cytokines, leading to a dampened T cell–driven autoimmune response.

The other agents operate through different parts of the immune system: Anakinra blocks the IL-1 receptor; Rituximab depletes B cells by targeting CD20; Tocilizumab blocks the IL-6 receptor. None of these are selective T cell costimulation modifiers like abatacept.