STAT1 IMPLICATION IN THE IMMUNE-RESPONSE TO SUPERANTIGENS IN-VIVO

We analyzed the activation and changes in the protein level of STAT1 a s a consequence of in vivo treatment with superantigens. Ninety minute s after i.p. injection of the staphylococcal enterotoxin B (SEE), a co mplex containing STAT1 that was able to specifically bind to DNA conta ining GAS-like sequences was activated in mouse splenocytes. This comp lex had the same characteristics as that induced by IFN-gamma in sever al in vitro systems. Activation of the complex was inhibited by cyclos porin A, and Abs against IFN-gamma severely decreased the amount of co mplex detected, When splenocytes were analyzed 24 h after SEE treatmen t, a high increase in the amount of the STAT1 isoforms, STAT91 and STA T84, was observed by Western analysis, but binding to GAS-like sequenc es was clearly decreased when compared with analysis at 90 min, Nevert heless, when SEE was injected a second time 24 h after the first injec tion, the binding of STAT1 to GAS-like sequences had risen again, This approach corroborates the implication of IFN-gamma in the response to superantigens in vivo and shows the relevance of analysis of transcri ption factors in defining the molecular events involved in the immune response.