Immunosuppressant
A drug that reduces immune system activity, used to prevent transplant rejection and treat autoimmune diseases. Cyclosporine is the most prominent peptide immunosuppressant, inhibiting calcineurin to suppress T-cell activation. Glatiramer acetate modulates immunity in multiple sclerosis.
Technical Context
Cyclosporine mechanism: binds to the intracellular protein cyclophilin → the cyclosporine-cyclophilin complex inhibits calcineurin (a serine-threonine phosphatase) → prevents dephosphorylation of NFAT (nuclear factor of activated T-cells) → NFAT cannot translocate to the nucleus → IL-2 gene transcription is blocked → T-cell activation and proliferation are inhibited. Cyclosporine's discovery (from the fungus Tolypocladium inflatum) and development in the 1980s revolutionised organ transplantation by enabling effective immunosuppression. Glatiramer acetate mechanism: a random polymer of L-alanine, L-glutamic acid, L-lysine, and L-tyrosine that modulates the immune response in MS through multiple mechanisms — promoting anti-inflammatory Th2 cells, inducing regulatory T cells, and competing with myelin antigens for MHC binding. Corticotropin (ACTH) has immunomodulatory effects beyond adrenal steroid stimulation, acting directly on melanocortin receptors on immune cells.