Enhanced intestinal transepithelial antigen transport in allergic rats is mediated by IgE and CD23 (Fc epsilon RII)

We previously reported that active sensitization of rats resulted in the ap pearance of a unique system for rapid and specific antigen uptake across in testinal epithelial cells. The current studies used rats sensitized to hors eradish peroxidase (HRP) to define the essential components of this antigen transport system. Sensitization of rats to HRP stimulated increased HRP up take into enterocytes (significantly larger area of HRP-containing endosome s) and more rapid transcellular transport: compared with rats sensitized to an irrelevant protein or naive control rats. Whole serum but not IgE-deple ted serum from sensitized rats was able to transfer the enhanced antigen tr ansport phenomenon. Immunohistochemistry demonstrated that sensitization in duced expression of CD23, the low-affinity IgE receptor (Fc epsilon RII), o n epithelial cells. The number of immunogold-labeled CD23 receptors on the enterocyte microvillous membrane was significantly increased in sensitized rats and was subsequently reduced after antigen challenge when CD23 and HRP were localized within the same endosomes. Finally, pretreatment of tissues with luminally added anti-CD23 antibody significantly inhibited both antig en transport and the hypersensitivity reaction. Our results provide evidenc e that IgE antibodies bound to low-affinity receptors on epithelial cells a re responsible for the specific and rapid nature of this novel antigen tran sport system.