Which immunosuppressive drug directly blocks IL-2 production?

The immunosuppressive drug that directly blocks IL-2 production is Cyclosporin. This drug works by inhibiting the activation of T cells, which is critical for initiating the immune response. Specifically, Cyclosporin binds to cytoplasmic proteins known as cyclophilins, and this complex then inhibits calcineurin, a phosphatase enzyme necessary for the dephosphorylation of nuclear factor of activated T-cells (NFAT). Once NFAT is dephosphorylated, it translocates to the nucleus to promote the transcription of IL-2 and other cytokines essential for T cell proliferation and activation. By blocking these mechanisms, Cyclosporin effectively reduces IL-2 production, thereby suppressing the immune response.

Other drugs mentioned, while also immunosuppressive, work through different mechanisms. For instance, OKT3 is a monoclonal antibody that targets CD3 on T cells, leading to their depletion or inactivation, rather than directly inhibiting the production of IL-2. Azathioprine is a pro-drug that interferes with DNA synthesis, affecting rapidly dividing cells like lymphocytes but does not specifically block IL-2 production. Sirolimus, on the other hand