Cyclosporine is an immunosuppressant that inhibits calcineurin by binding to cyclophilin.
Cyclosproine, tacrolimus, and pimecrolimus are all calcineurin inhibitors. Calcineurin is a phosphatase that is activated when in the presence of calmodulin and calcium that is necessary for cytokine synthesis within T cells. It does so by dephosphorylating nuclear factor of activated T-cells, cytoplasmic 1 (NFAT-1). Ultimately, inhibiting calcineurin prevents interleukin-2 (IL-2) production, which decreases the release of histamine and inflammatory cytokines and prevents T cell proliferation.
As noted above, cyclosproine, tacrolimus, and pimecrolimus are all calcineurin inhibitors, however, their associated mechanisms of action differ: