Suppressive effect of antibiotic siomycin on antibody production.

The antibiotic thiazole compound siomycin, which we have found from the culture broth of Actinomycetes (strain No.806097) in search of antibody production inhibitor, showed the in vitro immunosuppressive property against B-cells stimulated with T-cell independent antigen DNP-LPS (dinitrophenyl-lipopolysaccharide) while it also showed inhibitory effect against T-cell proliferation. Its inhibitory mechanism was considered to be different from that of FK506, the representative of T-cell immunosuppressant. Moreover, siomycin showed inhibitory effect in both T-cell dependent and independent murine antibody production models and decreased the severity in murine collagen arthritis model. Therefore, siomycin is a unique immunosuppressant which has potential for the treatment of some antibody-mediated diseases.