INHIBITORY EFFECT OF SOMATOSTATIN ON HUMAN T-LYMPHOCYTES PROLIFERATION

Somalostatin (SOM) was originally described as a growth hormone releas e inhibiting factor, but SOM and its specific receptors (SOM-r) have b een shown to be expressed on both normal and activated T and B lymphoc ytes and other immunocompetent cells. In the present study we have dem onstrated that SOM strongly inhibits the proliferation of human T lymp hocytes when stimulated by PHA, Con A or alloantigens. However, SOM wa s most effective when the T cells were stimulated by an alloantigen ra ther than a polyclonal activator such as PHA and ConA. Moreover, SOM s trongly inhibited the expression of activation markers such as CD69 an d CD25 that are expressed on T lymphocytes during alloantigen stimulat ion. SOM also inhibited both CD28 and CD2 mediated T cell proliferatio n. Whereas proliferation of T cells induced by the engagement of CD3 a ntigen using specific mAbs was only marginally affected. Our results w ould support the concept that in humans SOM plays a key role in the mo dulation of T cell activation by interfering with the antigen-independ ent pathways CD2 and CD28. (C) 1998 International Society for Immunoph armacology.