Inhibitory effect of somatostatin-14 and some analogues on human natural killer cell activity

The effect of somatostatin-14 (SST) and the SST analogues SMS and RC160 on human natural killer (NK) activity mediated by large granular lymphocytes (LGL), as well as on IL-2- and/or anti-CD16 monoclonal antibody (mAb)-induced activation of these cells, was investigated. The NK activity of LGL was studied by the release of 51Cr by the erythroleukemia-derived cell line K562, whereas 51Cr release by the P815 murine mastocytoma-derived cell line, for which lysis was redirected by the use of an anti-CD16 mAb, was used to study the cytolytic potential of these cells. IL-2 was used at the final concentration of 100 IU and was incubated overnight with LGL. SST and the analogues, added to these systems at final doses ranging from 10(-12) to 10(-5) M, were inhibitory of the NK cell activity to K562, with a dose-response curve starting from 10(-8) M and reaching a significant level at 10(-6) M. On the contrary, no effect was observed on the redirected killing assay to P815 and on the IL-2-induced activation of NK cells. These results provide additional evidence for the immunomodulatory action of somatostatin.