RANTES-ACTIVATED HUMAN T-LYMPHOCYTES - A ROLE FOR PHOSPHOINOSITIDE 3-KINASE

RANTES (regulated on activation, normal T cell expressed and secreted) , a member of the chemokine family, is a potent chemoattractant for CD 4(+)/CD45RO human T lymphocytes, but the signal-transduction mechanism s utilized by RANTES are poorly defined. In freshly isolated human T l ymphocytes loaded with fura-2 acetoxymethyl, the CD3 mAb, UCHT-1, but not RANTES, elicited elevation of intracellular calcium levels. Howeve r, RANTES produced a bell-shaped chemotactic response and an increase in polarization of the T lymphocytes. Immunoprecipitates of phosphoino sitide (PI) 3-kinase, derived from T lymphocytes stimulated with RANTE S, contained increased in vitro PI 3-kinase activity compared with tha t present in immunoprecipitates derived from vehicle-treated cells. RA NTES induction of PI 3-kinase activity was maximal at 10 to 100 ng/ml. Furthermore, the fungal metabolite, wortmannin, which is a potent PI 3-kinase inhibitor, inhibited RANTES-induced T lymphocyte migration, p olarization, and increased PI 3-kinase activity. Our results show that RANTES activation of T lymphocytes seems to be independent of detecta ble elevation of cytosolic-free calcium, but the functional effects of chemotaxis and polarization, induced by RANTES, seem to involve the p utative PI 3-kinase signal-transduction pathway.