Sensitisation of gut-associated lymphoid tissue during oral immunisation.

The time course of appearance of sensitised lymphocytes was studied in rabbits fed 0.1% bovine serum albumin (BSA). Antigen reactive cells (ARC) were detected in Peyer's patches at 1 week, prior to both the appearance of primed cells in the spleen and the detection of circulating anti-BSA antibody. Systemic immunisation with 2 mg BSA induced sensitised cells in the spleen and Peyer's patches. No evidence of an early appearance of sensitised cells in the mucosal cell population was found. These data support the postulates that the initial lymphocyte sensitisation to ingested soluble antigen occurs in Peyer's patches, that this lymphoid tissue provides a significant contribution to systemic immunity following oral and parenteral immunisation, and that the mucosal lymphocyte population is not involved in the early phase of sensitisation to ingested antigen.