Suppression of adjuvant arthritis in rats by boar seminal immunosuppressive fraction.

OBJECTIVE The effect of the immunosuppressive fraction of boar seminal vesicle fluid (ISF) was tested on the manifestation of adjuvant arthritis (AA) in rats. METHODS The inhibitory effect of ISF on mitogen-stimulated proliferation of rat lymphocytes was evaluated by immunoassay using bromodeoxyuridine incorporation. Adjuvant arthritis was induced in male Long Evans rats with Mycobacterium butyricum in adjuvant. ISF was administered at the time of the induction of arthritis. At the time of maximal manifestation of the disease, the hind paw swelling and thymus weight were estimated. IgM and IgG in the rat blood sera were quantified by sandwich ELISA. Serum corticosterone was analyzed by radioimmunoassay. Serum NO2-/NO3-were estimated by diazotation. Serum albumin was measured spectrophotometrically. The expression of IL-6 mRNA in peritoneal macrophages was estimated by dot-blot hybridization. RESULTS Treatment of arthritic rats with ISF attenuated hind paw edema. The production of IgG subclasses dropped in ISF-treated AA rats. The thymus mass and serum albumin concentration were partially restored due to the ISF treatment. Serum corticosterone as well as NO2-/NO3- concentrations were reduced by the ISF effect. The expression of IL-6 in peritoneal macrophages was inhibited in AA rats after ISF treatment. CONCLUSION ISF attenuated the manifestation of AA in rats and mitigated the inflammation. Immunoglobulin production was most probably inhibited by the decreased proliferation of B lymphocytes.