In vivo cytokine responses in gut-associated lymphoid tissue (GALT) and spleen following oral administration of staphylococcal enterotoxin B.

The mechanisms responsible for oral tolerance have been analyzed using various antigens. The induction of oral nonresponsiveness to low doses of Staphylococcal Enterotoxin B (SEB), in which SEB-reactive clonal anergy and deletion are involved, has also been confirmed. However, few reports have examined the cytokine milieu of the mucosal and peripheral lymphoid tissue during tolerance induction after the oral administration of SEB. In this study, to elucidate the mechanism responsible for the oral tolerance to low dose of SEB, the cytokine responses of the gut-associated lymphoid tissues (GALT) and the spleen were examined using the reverse transcription-polymerase chain reaction (RT-PCR) method. After the oral administration of a single low dose of SEB, the expressions of Th2 and TGF-beta, and to a lesser extent Th1 mRNA were observed in the mucosa. In contrast, following repeated oral low doses of SEB, in a manner different from previous results using conventional antigens, no cytokine enhancements were demonstrated in the GALT or the spleen. In conclusion, the involvement of unknown inhibitory or regulatory cytokines, together with SEB-reactive clonal anergy and deletion, is suggested in the induction of oral tolerance to low dose SEB.