The immune privilege of the anterior chamber (AC) of the eye is largely due to the active down-regulation of systemic delayed-type hypersensitivity (DTH) that is evoked when antigens are introduced into this ocular compartment. This antigen-specific suppression of DTH has been termed anterior chamber-associated immune deviation (ACAID) and has been demonstrated with a wide variety of antigens. Previous studies have shown that antigens introduced into the AC are processed by resident antigen-presenting cells which then migrate to the spleen where they transmit a signal that culminates in the generation of regulatory cells that prevent the development of DTH. Although considerable effort has focused on the nature of the ocular phase of ACAID, the role of the spleen has been largely ignored. The present study tested the hypothesis that B cells are the essential cell population responsible for the splenic phase of ACAID. Splenectomy prevented the induction of ACAID; however, introduction of B cell-enriched spleen cells into the AC of splenectomized mice restored the hosts' capacity to develop ACAID. The same effect, however, could not be produced with B cell-depleted spleen cells. B cell depletion of eusplenic mice by chronic administration of anti-mu antiserum prevented the development of ACAID and thus, had the same of effect as splenectomy. The results indicate that an intact B cell population is necessary for the induction of ACAID. These findings also support the hypothesis that antigens arising in the AC and subsequently delivered to spleen are captured by B cells and presented to T cells in a manner that promotes the development of down-regulatory T cells.