IMMUNOTOLERANCE INDUCED BY INTRATESTICULAR ANTIGEN PRIMING - EXPRESSION OF TGF-BETA, FAS AND FAS LIGAND

The authors have previously reported that an injection of S-antigen (S -Ag) into rat testes prior to immunization induces systemic tolerance (designated orchidic tolerance) and protects the animals from experime ntal autoimmune uveoretinitis (EAU) and that the signal for orchidic t olerance induction emigrates from the testis within a few hours after antigen priming of the testis. In order to understand the mechanism by which the signal or signal carrier is generated, they determined in t his study changes in immunoreactivity for transforming growth factor-b eta (TGF-beta), IFN-gamma, IL-2, Fas and Fas ligand in the testis foll owing an injection of S-Ag. Immunoreactivity for TGF-beta increased wi th time, reaching a maximum in six hours and declining thereafter. The time required for the maximum expression of TGF-beta coincided well w ith the time-dependent profile of orchidic tolerance signal generation within the testis. Little or no immunoreactivity was observed for IFN -gamma and IL-2 in normal (control) and S-Ag-injected testes. Immunore activity for Fas and Fas ligand was detected both in control and exper imental testes and did not change appreciably with time following Ag-p riming of the testis. Fas immunoreactivity was found in spermatids and virtually absent in the interstitial tissue, while Fas ligand immunor eactivity was primarily associated with the interstitial cells such as Leydig cells. Fas ligand immunoreactivity was very weak, if any, in t he germ cells and Sertoli cells. These results suggest that TGF-beta a nd Fas ligand expressed in MHC-positive interstitial cells may play an important role in the generation of orchidic tolerance induction sign al. A preliminary study showed that splenocytes preincubated with test is extracts and S-Ag, when transferred to naive rats, induced systemic tolerance in recipient animals. Inclusion of anti-TGF-beta or a carbo xyl terminal peptide of Fas in the testis extract reduced the potency of incubated splenocytes to induce systemic tolerance in recipient rat s. These results indicate that generation of the orchidic tolerance si gnal does not require the anatomical structure of the testis but is me diated by molecular entities such as TGF-beta and Fas ligand.