What role do immunophilins play in the action of immunosuppressants such as cyclosporine?

Immunophilins are a class of proteins that have a crucial role in the mechanism of action of various immunosuppressants, especially cyclosporine. These proteins bind specifically to immunosuppressants, forming a complex that is essential for the drug's pharmacological effect. In the case of cyclosporine, when it binds to the immunophilin cyclophilin, the resulting complex inhibits the activity of calcineurin, which is a critical protein phosphatase involved in the signaling pathways that lead to the activation of T-lymphocytes and the subsequent production of cytokines.

This binding is pivotal because it modulates T-cell activation and reduces the immune response, which is particularly significant in the context of organ transplantation and autoimmune diseases, where lowering the immune response is desired to prevent rejection or manage symptoms. Therefore, the interaction of cyclosporine with immunophilins is a key step in its immunosuppressive action.