<p>Tacrolimus is a macroiide immunomodulator produced by fungus, Streptomyces tsukubaensis. It has been demonstrated that Tacrolimus inhibits T-lymphocyte activation by first binding to an intracellular protein, FKBP-12. A complex of Tacrolimus-FKBP-12, calcium, calmodulin, and calcineurin is then formed and the phosphatase activity of calcineurin is inhibited. This leads to a general decrease in the entire inflammatory cascade.</p>