Cyclosporine

Cyclosporine is an immunosuppressive drug that inhibits T-cell activation by blocking calcineurin signaling. Its use substantially improved outcomes in organ transplantation.

Calcineurin: A calcium- and calmodulin-dependent phosphatase that activates transcription factors involved in immune responses. Cyclosporine-bound cyclophilin inhibits this phosphatase, preventing T-cell activation.
Organ transplantation: The transfer of an organ from a donor to a recipient to replace a failing organ. Cyclosporine helps prevent the recipient's immune system from rejecting the graft.
Tolypocladium inflatum: A soil fungus from which cyclosporine was first isolated. This organism produced the compound that became cyclosporine.
Azathioprine: An immunosuppressive antimetabolite that interferes with purine synthesis and lymphocyte proliferation. It suppresses immune responses through a different mechanism and was used in older transplant regimens.
Cyclophilin: A family of proteins that bind cyclosporine and also catalyze protein folding. Cyclophilin carries cyclosporine to calcineurin, forming the inhibitory drug–protein complex.
Graft rejection: An immune response that damages transplanted tissue recognized as foreign. Preventing rejection is the main reason cyclosporine is used after transplantation.
Jean-François Borel: A Swiss immunologist whose research helped establish cyclosporine's immunosuppressive activity. Borel's experimental work helped reveal the drug's selective effects on lymphocytes.
Mycophenolate mofetil: An immunosuppressive prodrug that inhibits inosine monophosphate dehydrogenase and limits lymphocyte nucleotide synthesis. It offers a distinct mechanism and is often combined with calcineurin inhibitors.
NFAT: A family of transcription factors that regulate immune-response genes after activation by calcineurin. Calcineurin inhibition keeps NFAT inactive and reduces interleukin-2 transcription.
Kidney transplantation: The surgical placement of a donor kidney into a recipient with kidney failure. Kidney transplantation was among the settings in which cyclosporine's benefits became evident.

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