Takumi Sasaki

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.

The purification and biological activity of a macrophage-derived factor with interleukin 1-like activities from guinea pigs

A macrophage-derived factor with interleukin 1-like activity was purified from culture supernatant of muramyl dipeptide-stimulated peritoneal exudate macrophages of guinea pigs. Starting with serum-free culture supernatant, the purification was carried out by gel permeation chromatography, affinity chromatography on procion red agarose, removal of carry-over serum proteins by Sepharose-coupled antibodies against bovine serum proteins, anion exchange chromatography and hydrophobic chromatography. The purified sample potentiated the phytohemagglutinin-induced thymidine uptake of thymocytes with a 50% effective concentration of 9.6 X 10(-11) M. The sample showed a single band in polyacrylamide gel electrophoresis, and a 65 kDa band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis by silver staining. A single peak of activity was detected by thymocyte assay at the position corresponding to the stained band in both of the electrophoretic analyses. The purified factor had activities to potentiate the antigenic activation of sensitized T cells for the production of a lymphokine, macrophage migration inhibitory factor, and also the proliferative response of sensitized T cells to antigen. Thus, the 65 kDa factor has activities to modulate various T cell responses in guinea pigs such as interleukin 1 does in other species. The molecular relationship of the 65 kDa macrophage factor to interleukin 1 remains to be determined.

Prevention of collagen-induced arthritis with the superantigen, Staphylococcal enterotoxin B

Abstract Intravenous administration of Staphylococcal enterotoxin B (SEB) was found to induce T cell tolerance in DBA/l mouse which is known to be susceptible to collagen-induced arthritis (CIA), a mouse model of human rheumatoid arthritis. After repeated administration of SEB, the proliferative response to SEB of spleen T cell was significantly decreased. The SEB-reactive Vβ8 TCR + T cell population in the treated mice was reduced only partially but the proliferative response of spleen T cells to anti-Vβ8 + TCR monoclonal antibody was profoundly decreased, indicating that the tolerance to SEB is induced mainly by induction of the anergic state in Vβ8 TCR + T cell population and to some extent by the partial deletion of these lymphocytes. In SEB-treated mice, the incidence of CIA was decreased to about 20% of that of control mice. The severity of the disease in mice which developed CIA was also decreased in the SEB-treated mice. Furthermore, the proliferative response to type II collagen (CII) of the spleen T cell of disease-suppressed mice was significantly impaired. The anti-CII IgG level in the serum of the SEB-treated mice was also decreased but only moderately. These results suggest the applicability of the superantigen-based therapy to Vβ-restricted, T cell-dominated autoimmune diseases.