The immunosuppressant action of cyclosporine appears to be due to :
Activation of NK cells
Blockade of tissue responses to inflammatory mediators
Inhibition of gene transcription of interleukins
Interference with antigen recognition
Cyclosporine and tacrolimus acts by inhibiting calcineurin, which is involved in the activation of NFAT. Final result of this process is increased transcription of IL-2 gene.
Sirolimus does not inhibit the transcription of IL-2 but interferes with its action. It inhibits the enzyme tyrosine kinase, known as mTOR (which is activated by IL-2).