INDUCTION OF THE INCREASED FYN KINASE-ACTIVITY IN ANERGIC T-HELPER TYPE-1 CLONES REQUIRES CALCIUM AND PROTEIN-SYNTHESIS AND IS SENSITIVE TOCYCLOSPORINE-A

Several alterations in T cell receptor-associated signal transduction have been observed following induction of anergy of T helper type 1 (T h1) clones, including a modified intracellular free calcium ([Ca2+](i) ) response and increased kinase activity associated with the protein t yrosine kinase p59(fyn). In the current study, we demonstrate that, al though the kinetics of acquisition of both of these signaling alterati ons correlated with the generation of anergy, a normal calcium respons e returned within 48 h after removal from the anergizing stimulus, whe reas the increased p59(fyn) activity persisted and the cells remained hyporesponsive. Generation of both the anergic state and the increased p59(fyn) activity was prevented in the presence of calcium-free mediu m, cycloheximide (CHX), or cyclosporin A (CsA), and could be mimicked by the calcium ionophore ionomycin. In contrast, the altered calcium r esponse was inhibited by stimulation in the presence of calcium-free m edium or CsA, but not CHX. Thus, surprisingly, these data suggest that a chronic elevation of [Ca2+](i) is proximal to and necessary for the increase in p59(fyn)-associated kinase activity observed in anergic T h1 clones. Increased p59(fyn) activity, but not the altered calcium re sponse, correlates with maintenance of the anergic state.