DEFECTIVE TCR STIMULATION IN ANERGIZED TYPE-2 T-HELPER CELLS CORRELATES WITH ABROGATED P56(LCK) AND ZAP-70 TYROSINE KINASE-ACTIVITIES

Development of IgE-mediated allergic conditions is dependent on the se cretion of a Th2 cytokine pattern, including IL-4, IL-5, and IL-13. Th e induction of anergy would be one mechanism to abrogate cytokine secr etion by Th2 cells, which may be pivotal to the allergic response. We demonstrate here that incubation of cloned human CD4(+) phospholipase A(2) (PLA)-specific Th2 cells with antigenic peptide, in the absence o f professional APC, results in a state of nonresponsiveness. The anerg ic T cells failed to proliferate or secrete IL-4 in response to optima l stimulation with PLA and autologous, professional APC. Secretion of IL-5 and IL-13, however, was only partially inhibited. The anergic sta te of the Th2 cells was not associated with CD3 or CD28 downregulation . However, anergy did appear to be closely related to alterations in s ignaling pathways, mediated through the TCR, of the cells. In contrast to untreated Th2 cells, anergized Th2 cells failed to respond to anti -CD3 mAb with either increased tyrosine kinase activity or increased l evels of tyrosine phosphorylation of p56(lck) or ZAP70. A strong and s ustained intracellular calcium flux, observed in untreated Th2 cells i n response to anti-CD3 mAb, was absent in anergic Th2 cells. Furthermo re, the induction of anergy seems to represent an active process, asso ciated with increased levels of basal tyrosine kinase activity, cytoki ne production, and CD25 up-regulation in anergic Th2 cells. Together, our results indicate that anergy in Th2 cells is associated with defec tive transmembrane signaling through the TCR.