DIFFERENTIAL INDUCTION OF THE NF-AT COMPLEX DURING RESTIMULATION AND THE INDUCTION OF T-CELL ANERGY

Stimulation of human CD4(+) T-cell clones through the T-cell receptor (TcR) by high doses of specific peptide results in the induction of a long-lived state of nonresponsiveness that has been called anergy. Dur ing the induction of anergy, T cells are phenotypically similar to cel ls responding to an immunogenic stimulus. The amount of TcR at the cel l surface is downmodulated, whereas the CD2 and CD25 receptors are inc reased. When restimulated, however, anergic T cells fail to upregulate transcription of the IL-2 gene and in consequence do not produce IL-2 . In this study, we have compared the ability of various transcription factors to bind to their appropriate site on DNA. Factors were isolat ed from the nuclei of T cells that were in the induction phase of aner gy or were undergoing activation. The pattern of binding activity in r estimulated T cells is consistent with the pattern that has previously been shown to regulate T-cell-specific expression of the IL-2 and the beta chain of the TcR genes. The measured binding to a TCF-1 site is the same in the nuclei of resting, activated, and anergized cells. The inducible factors NK-kappa B, beta E2, CD28RC, and AP-1 are not expre ssed in resting cells and are twofold lower in anergized as compared w ith activated cells. In contrast, anergic T cells express approximatel y eightfold lower amounts of NF-AT, a member of the class of inducible factors that regulates IL-2 gene transcription. The failure to induce NF-AT completely may be a consequence of a diminished calcium flux, s ince the PKC pathway was apparently intact. It was found that the calc ium ionophore ionomycin could either induce anergy or abrogate the ind uction of nonresponsiveness according to the dose, also suggestive of differences in calcium signaling. The pattern of expression of transcr iption factors during the induction of T-cell anergy is consistent wit h the inability of anergic cells to produce IL-2. These results demons trate that there are differences in the early nuclear events character istic of stimuli, the outcome of which leads to cells that are phenoty pically similar, but are functionally different.