What role does interleukin-2 play in T-cell activation that is inhibited by cyclosporine?

Interleukin-2 (IL-2) is a key cytokine involved in the activation and proliferation of T-cells. After T-cells are activated by antigen presentation and costimulatory signals, IL-2 is produced primarily by activated T-cells and acts in an autocrine and paracrine manner. The binding of IL-2 to its high-affinity receptor on T-cells stimulates their proliferation, differentiation, and survival, leading to a robust immune response.

Cyclosporine works by inhibiting calcineurin, a phosphatase that is crucial for the activation of transcription factors that ultimately lead to the synthesis of IL-2. By preventing IL-2 production, cyclosporine effectively reduces the proliferation of T-cells, which is why it is used as an immunosuppressive agent in various clinical settings. This role of IL-2 in T-cell proliferation is fundamental to the immune response, making it central to the mechanism by which cyclosporine interferes with T-cell activation and proliferation.