P-100. effect of somatostatin in human t cells activation

In the present study we have investigated the effects of somatostatin (SS) on activation and proliferation of human peripheral blood lymphocytes during stimulation by either mitogens, alloantigen or via CD2 and CD28 surface molecules. We have found that SS strongly inhibited the expression on T lymphocytes of activation antigens such as IL2 receptor (CD25) and CD69 after stimulation with allogenic cells. In addition, T cell proliferation in mixed lymphocytes culture (MLC) was strongly reduced by the presence of SS. Importantly, SS consistently inhibited both CD28-and CD2-mediated T cell proliferation. By contrast T cell antigen receptor complex (CD3/TCR) driven proliferation of PB T cells was only marginally affected. Altogether these findings would suggest that SS regulates T cell activation and proliferation by interfering with signals mediated by CD2 and CD28 accessory molecules rather then acting on CD3/TCR activation pathway.