INCREASED PROLIFERATION, CYTOTOXICITY, AND GENE-EXPRESSION AFTER STIMULATION OF HUMAN PERIPHERAL-BLOOD T-LYMPHOCYTES THROUGH A SURFACE GANGLIOSIDE (GD3)

Previous studies have suggested that gangliosides have an important ro le in cell signaling and recognition. However, their specific function in these processes has not been clearly defined. A mAb, R24, that rea cts specifically with a cell surface ganglioside (GD3) has been demons trated to stimulate proliferation of T cells derived from human periph eral blood. In this study, we have investigated the mechanisms by whic h the R24 mAb affects T cell functions. We have observed that the R24 mAb stimulates GD3+ T cell proliferation, cytotoxicity, and surface ma rker expression of IL-2R alpha-chain, IL-2R beta-chain, HLA-DR, CD11a, and CD11c. Additionally, IFN-gamma activity but not IL-1, IL-2, or IL -4 activity was present in culture supernatants 72 h after R24 stimula tion. In some donors, increased IL-6 and TNF-alpha activity also was d etected after R24 treatment. Furthermore, R24 treatment resulted in tr anslocation of c-rel, but little or no NFkappaB p50 or p65, from the c ytoplasm to the nucleus and an increase of NFkappaB binding complexes containing c-rel and p50. This treatment also caused increased tyrosin e phosphorylation of specific protein substrates. R24-stimulated incre ases in proliferation, cytotoxicity, and cell surface protein expressi on could be blocked by cyclosporin and staurosporin, indicating that c yclophilin/calcineurin and protein kinase C may be involved in the R24 signaling pathway. Additionally, herbimycin A, a tyrosine kinase inhi bitor, blocked the R24-stimulated increase in proliferation but not cy totoxicity at concentrations consistent with specificity for tyrosine kinases. These results suggest that multiple biochemical pathways are involved in the activation of human T cells by R24.