IN-VIVO ANERGIZED CD4(-CELLS HAVE DEFECTIVE EXPRESSION AND FUNCTION OF THE ACTIVATING PROTEIN-1 TRANSCRIPTION FACTOR() T)

The transcription factor activating protein-1 (AP-1) contributes signi ficantly to the regulation of IL-2 gene expression during T cell activ ation and has been suggested to play a unique role in T cell anergy in vitro. In this study we have used the superantigen staphylococcal ent erotoxin A to investigate the regulation of AP-1 in T cell anergy in v ivo. Repeated injections of staphylococcal enterotoxin A induce a stat e of anergy in CD4(+) T cells, characterized by reduced expression of IL-2 at mRNA and protein levels, The perturbed IL-2 response in anergi c T cells correlated with reduced DNA binding activity of the transcri ption factors AP-1 and Fos/Jun-containing NF-AT, Using AP-1-luciferase reporter transgenic mice, we now demonstrate the lack of AP-1-depende nt transcription. AP-1 activity is controlled by synthesis of its subu nits Fos and Jun and by posttranslational phosphorylations. Analysis o f Fos and Jun protein levels revealed no major differences in the expr ession of Jun proteins, but a marked decrease in c-Fos in anergic T ce lls. Experiments in transgenic mice overexpressing c-Fos (H2-c-fos) sh owed reconstituted AP-1 DNA binding, In contrast, the AP-1-driven tran scription and IL-2 production remained suppressed, The Jun N-terminal kinase is known to play a critical role in regulating AP-1 trans-activ ation. Analyses of Jun N-terminal kinase demonstrated normal protein a mounts, but reduced enzymatic activity, in anergic compared with activ ated CD4+ T cells, This suggests that in vivo anergized T cells have d efects in the AP-1 pathway due to both reduced protein expression and perturbed posttranslational modifications.