Abstract
Regulatory T cells are induced by oral administration of an antigen, but the physiological requirements and localization of the inductive sites are largely unknown. Using an adoptive transfer system of cells transgenic for ovalbumin T-cell receptor (OVA TCR tg), we found that antigen-specific CD4+ T cells were activated in the liver-draining celiac lymph node (CLN) shortly after ovalbumin feeding, and that a significantly higher proportion of the T cells in the CLN developed into the putative regulatory phenotype [co-expressing CD25 with the glucocortico-induced tumour necrosis factor (TNF) receptor family related gene (GITR), cytotoxic T-lymphocyte antigen (CTLA)-4 and CD103] than in Peyer's patches, the mesenteric and peripheral lymph nodes and the spleen. In addition, a particularly high level of expression of CD103 on the OVA-specific T cells in the CLN may favour homing to the epithelium of the intestine. While equally suppressive, OVA tg T cells isolated from the CLN of OVA-fed DO11.10 mice were less dependent on transforming growth factor (TGF)-beta for suppression than cells isolated from the peripheral and mesenteric lymph nodes, which indicates the involvement of an additional suppressive mechanism. The expression of FoxP3 was not up-regulated in any of the lymph node compartments studied. Our phenotypic and functional findings suggest that the induction of regulatory T cells in the CLN may be relevant in the control of the immune response to dietary antigens.