A mucosal IgA-mediated excretory immune system in vivo

The capacity of mucosal IgA Abs to serve as an excretory immune system in v ivo was investigated. Mire expressing a transgenic TCR mere immunized intra gastrically with the cognate Ag to elicit a vigorous mucosal IgA Ab respons e. Soon after i.v. challenge, Ag was detected within the epithelial cells o f the small intestinal crypts and to a lesser degree within the epithelial cells higher up the villi, paralleling the gradient in expression of the po lymeric Ig receptor and the transport of its ligand, oligomeric IgA. Uptake of Ag into the epithelial cells occurred only from the basolateral aspect and only when Ag complexed to IgA Ab could be present in the lamina propria , The results support the concept that local IgA Abs can excrete Ags from t he body by transporting them directly through mucosal epithelial cells, usi ng the same mechanism that transports free IgA into the mucosal secretions.