Reversible effects on B and T cells of the gut-associated lymphoid tissues in rats malnourished during suckling: impaired induction of the immune response to intra-Peyer patches immunization with cholera toxin.

To define the alterations provoked by malnutrition during suckling (20 pups/dam) in the gut-associated lymphoid tissues of rats, Peyer patch (PP) and mesenteric lymph node (MLN) cells were studied by flow cytometry. After weaning (21 days of age), rats malnourished during suckling (MNR) showed an increase in the CD4+ CD45RC+ subset together with a decrease in the CD4+ CD45RC- subset (P < 0.01). These alterations remained even after 3 weeks of refeeding with stock diet. The CD4+CD8+ subset was not increased in the MNR, indicating that a release of cortical thymocytes did not occur. At weaning the percentage of CD4+Thy1+ cells was decreased in the MNR, indicating a low number of cells released from the thymus. When the B cell lineage was studied, we found a decreased percentage of precursors in the bone marrow and a decreased percentage of mature B cells in the periphery. When the MNR were immunized intra-PP with cholera toxin (CT) after 1 week of refeeding, the specific IgG and IgA and IgM antibody-forming cells (measured by ELISPOT) were diminished in the PP, MLN, and spleen when compared to the age-matched controls (P < 0.001). These results were coincident with the ELISA titers obtained in the sera and in the intestinal fluids. When CT was administered after 2 weeks of refeeding, the number of IgM anti-toxin AFC approached control values, but the number of IgA and IgG AFC continued to be low. When 3 weeks of refeeding was allowed before the CT delivery, the immune response in the MNR approached control values. These results indicate that malnutrition during suckling provokes alterations in B and T lymphocytes and produces a lack in the induction of the primary and secondary immune responses in the GALT which reversed after 3 weeks of refeeding.