DEFECTIVE IMMUNE-RESPONSE AND FAILURE TO INDUCE ORAL TOLERANCE FOLLOWING ENTERAL EXPOSURE TO ANTIGEN IN BROILERS AFFLICTED WITH STUNTING SYNDROME

Infectious stunting syndrome (SS) in broilers is a multi-symptomatic d isease that includes lesions in the intestinal tract. We investigated whether these lesions impeded functions of the intestinal immune syste m. Two functions were studied: the capacity to generate 1) immune resp onses to a resident pathogen (E, coli) of the gut and to a parenterall y administered antigen (beta-casein), and 2) tolerance to an orally ad ministered antigen (beta-casein). SS was induced in day-old broilers b y an inoculum prepared from SS afflicted broilers. After onset of SS, immune responses (or absence of, in the case of tolerance) were studie d by specific antibody production and T lymphocyte proliferation. Immu ne responses were induced by subcutaneous immunization of broilers aga inst beta-casein or following natural exposure to enteric E. coli. Ora l tolerance was induced by a single feeding of beta-casein in gelatine capsules. Both enteral anti-E, coli and parenteral anti-beta-casein r esponses were significantly reduced in SS birds. SS afflicted broilers did not develop beta-casein-specific oral tolerance. These results in dicate dysfunction of both the intestinal immune system and that of sy stemic acquired immune responses in SS.