SPLENECTOMY ABROGATES THE INDUCTION OF ORAL TOLERANCE IN EXPERIMENTALAUTOIMMUNE UVEORETINITIS

Oral administration of uveitogenic antigens inhibits the development o f experimental autoimmune uveoretinitis (EAU) and the cellular immune response initiated by these antigens. The mechanism of oral tolerance is not completely clear, but accumulating data indicate that suppresso r cells are actively involved in this process. The spleen is known to harbor suppressor cells and their precursors and the present study was aimed at testing the role of this organ in the induction of oral tole rance by S-antigen (S-AG). We report here that: (a) splenectomy abroga ted the induction of oral tolerance; unlike in sham operated controls, feeding with S-Ag did not inhibit the development of EAU in splenecto mized rats; (b) spenectomized rats responded with higher cellular immu ne responses than did sham operated controls, but feeding with S-Ag in hibited these responses in both groups of animals; (c) splenectomy als o abrogated the adoptive transfer of tolerance : EAU induction was inh ibited in sham operated recipients of splenocytes from S-Ag fed donors but not in the splenectomized recipients. The data thus indicate that the spleen plays an important role in the induction of oral tolerance , perhaps by acting as the site for induction and/or amplification of cells with suppressor activity.