Splenic B Cells Act as Antigen Presenting Cells for the Induction of Anterior Chamber-Associated Immune Deviation

PURPOSE. To characterize the role of B cells in the induction of anterior chamber-associated immune deviation (ACAID). METHODS. An in vitro model of the ACAID spleen was used to recapitulate the events that occur when antigen is introduced into the anterior chamber of the eye and culminates in the appearance of antigen-specific, CD8⁺ suppressor cells. RESULTS. In vitro-generated suppressor cells mimicked those produced by anterior chamber injection of antigen, as shown by their antigen specificity, surface expression of CD8, and capacity to suppress DTH, which is mediated by previously immunized T cells. B cells were found to be necessary for suppressor cell development. The B cell receptor (BCR) was necessary for the induction of ACAID and conveyed antigen specificity to the suppressor T cells. Lysosomal acidification of internalized antigen was necessary for B cells to induce ACAID; however, transporter of antigen processing (TAP) was not required for the generation of ACAID. CONCLUSIONS. The results suggest that B cells use the BCR to capture and internalize antigen from ACAID-inducing macrophages. Lysosomal acidification of the captured antigen is essential for the processing of the ACAID antigen before TAP-independent presentation to suppressor cells.