LONG-TERM INOSITOL PHOSPHATE RELEASE, BUT NOT TYROSINE KINASE-ACTIVITY, CORRELATES WITH IL-2 SECRETION AND NF-AT INDUCTION IN ANTI-CD3-ACTIVATED PERIPHERAL HUMAN T-LYMPHOCYTES

The cascade of events within the first few minutes of T cell stimulati on has been well characterized. Although many second messengers have b een shown to be necessary and sufficient for T cell activation in a nu mber of model systems, the rate-limiting step in peripheral T cells ha s not been demonstrated. To model effective versus ineffective CD3-med iated stimulation in peripheral T cells, we used two anti-CD3 mAbs tha t differ in their ability to stimulate purified T cells: OKT3, which c auses early second messenger generation but is unable to activate T ce lls without a second signal, and 64.1, which stimulates T cell prolife ration on its own. We found that tyrosine kinase activity was similar for both mAbs over a period of hours. However, the inositol phosphate response was stronger for 64.1 than for OKT3. To tie these events to g ene activation, we measured NF-kappa B and NF-AT activity in the nucle us after anti-CD3 stimulation. Both stimuli induced the appearance of the NF-kappa B components (c-Rel, p65 (RelA), and p50 (NF-kappa B1)) a nd NF-kappa B DNA binding activity in the nucleus. However, only 64.1 induced NF-AT in the nucleus, correlating with its ability to activate T cells. Thus, NF-AT induction and IL-2 secretion were correlated wit h the levels of inositol phosphate release but not with gross levels o f tyrosine kinase activity induced late following the response. On the other hand, NF-kappa B induction and IL-2 receptor expression occurre d even with the smaller second messenger response generated by OKT3. ( C) 1994 Academic Press, Inc.