The biological activities of the small peptide immunosuppressant

According to the previous studies, in which we used a monoclonal antibody 5 G1 that is specific for the human IL-2 receptor a-chain to screen a random hexa-peptide library and obtained the phage clone which has good combinativ e activities studied by Elisa, the consensus sequence motif C-S-S was revea led by DNA sequencing, the peptide Ac-XCSSXX-NH2 was synthesized, then puri fied by HPLC and confirmed by MS. To investigate the biological activities of the hexa-peptide, we constructed the vitro model of the lymphocyte proli feration experiment(LPE) induced by ConA and IL-2 and the vivo model with l iver transplanting of rat. In the LPE induced by ConA, the addition of hexa -peptide(250-31.25 mug/mL) had a significant inhibitory effect to LPE(P muc h less than0.01). The minimal inhibitory mass concentration is 31.25 mug/mL , with the inhibitory rate of 78.16%. In the LPE induced by IL-2, we obtain ed the same result as the LPE induced by ConA. So we can say that the pepti de realizes its immuno-suppresive effect by blocking the combination of IL- 2 and IL-2R. In the liver transplanting model of rat, the injection of the peptide to the operated rat in five days would prolong the survival time of the rat.