INTESTINAL IMMUNE-RESPONSE TO ESCHERICHIA-COLI ANTIGENS IN GERMFREE CHICKEN

  • 1 January 1977
    • journal article
    • research article
    • Vol. 32  (5) , 731-741
Abstract
The secretory intestinal immune response to live and heat-inactivated Escherichia coli O2 was studied in young germ-free chicks. A response to live organisms was evident from an infiltration of the intestinal mucosa with Ig[immunoglobulin]A and IgM-producing cells (IPC). Antibody associated with both Ig classes which was specific for E. coli O2 was demonstrated in saline extracts of contents from the small intestine. Repeated oral immunization with heat-killed E. coli O2 failed to stimulate serum or intestinal antibody. This finding reflected the complete absence of IPC within the intestinal mucosa of these birds. The IPC profile of unimmunized germ-free chicks was identical to that seen in chicks orally immunized with inactivated E. coli. An interesting feature of all gnotobiotic birds was a considerable elevation of serum IgM levels, compared to those of conventional birds, which was unassociated with immunization procedures. Serum IgG and IgA levels in gnotobiotes were much lower than those in the serum of conventional birds of comparable age. Studies on the fate of orally administered antigen using radiolabeled E. coli endotoxin indicated that a proportion remained intact as far down the intestinal tract as the cecum. Unaccountably high levels of low MW antigen in the feces suggested degradation, intestinal absorption and subsequent excretion of endotoxin fragments in the urine. The differences between the avian response and that observed in mammals are discussed in relation to the comparative roles of Peyer''s patches and the bursa of Fabricius in initiating intestinal immunity.