An investigation of the ability of orally primed and tolerised T cells to help B cells upon mucosal challenge.

The oral delivery of soluble antigens induces unresponsiveness to systemic challenge that can be demonstrated as a reduced ability of tolerised T cells to support B-cell expansion and antibody production. However, it remains controversial whether previously induced oral tolerance results in suppression or priming, or has no effect on B-cell responses upon oral challenge. Using a double adoptive transfer system, we primed or tolerised T cells (independently of B cells) with a high dose of fed antigen, and examined the ability of these primed or tolerised T cells to support B-cell clonal expansion in response to orally delivered conjugated antigen. We demonstrated directly in vivo that, in contrast to orally primed T cells, transgenic T cells tolerised by feeding a high dose of antigen are incapable of providing cognate help to support B-cell clonal expansion and antibody production in response to oral challenge. This defect appears to be a result of a reduced ability of orally tolerised transgenic T cells to clonally expand and migrate to B-cell follicles after oral challenge.