DEFICIENT INDUCTION OF THE IMMUNE-RESPONSE TO ORAL IMMUNIZATION WITH CHOLERA-TOXIN IN MALNOURISHED RATS DURING SUCKLING

Malnourished rats during suckling were orally immunized with cholera t oxin (CT) after different periods of refeeding. Intestinal fluids, ser a, and supernatant fluids from cultured mesenteric lymph node (MLN) ce lls were obtained after rats were given three doses of CT and analyzed by enzyme-linked immunosorbent assay (ELISA) to evaluate the specific antibody response. Serum-specific immunoglobulin G (IgG), IgA, and Ig M were severely diminished in malnourished rats immunized with three d oses of CT after 1 week of refeeding when compared with those of contr ols. Also, a decreased IgA ELISA titer of the intestinal fluids and ab rogation of the capacity to neutralize the CT in the intestinal ligate d loop test were found. When a booster was given at 113 days of age, t he immune response continued to be affected in the serum and the intes tinal fluid. The results from the analysis of the supernatant fluids f rom cultured MLN cells were coincident with those mentioned above. Whe n one dose of CT was administered into Peyer's patches (PP) after 1 we ek of refeeding, an impaired immune response was found in the intestin al fluid of malnourished rats during suckling compared with that of co ntrols. This result together with the analysis of supernatant from MLN and PP cell cultures suggests that antigen triggering in the PP was a ffected. When the refeeding period was extended to 30 days and then th e first dose of CI was administered, the antibody immune responses in intestinal fluid serum and supernatant fluid approached control values . These observations reinforce the fact that the gut-associated lympho id tissue immaturity of the rats when they received the first CT dose (at 28 days old) was the main reason for the decreased immune response observed in the experimental group.