| Abstract: | The influence of protein malnutrition on the IgA immune response was determined in BALB/c mice fed isocaloric diets containing 20% (control), 4%, or 2% protein. Mice fed the 2% protein diet for six weeks were severely protein malnourished and had drastically impaired IgA immune responses as evidenced by reduced intestinal wash IgA levels, a reduced IgA plaque-forming cells (PFC)/spleen response after oral immunization with sheep erythrocytes, and increased serum IgA levels. Moderately protein malnourished mice, generated by feeding the 4% protein diet for six to eight weeks, showed reduced intestinal wash IgA levels and increased serum IgA levels, yet the IgA PFC/spleen response was normal. Severely protein deficient mice reconstituted with normal Peyer's patch (PP) cells before oral immunization showed a partial recovery of the IgA PFC response when low numbers of cells were transferred. This recovery was due to the transferred B-cells suggesting that the malnourished mice had functional T-cells and nonfunctional B-cells. A slightly enhanced in vitro blastogenic response of PP cells from severely malnourished mice to Concanavalin A also indicated functional T-cells in the malnourished mice. Reconstitution with excess PP cells from well nourished mice yielded no recovery of the IgA PFC response because of the stimulation of T-suppressor (Ts) cells. Transfer of spleen, but not PP, cells from immunized malnourished mice to well nourished mice before oral immunization resulted in a reduced IgA PFC response when compared to mice receiving immune cells from well nourished donors. This reduction was also determined to be due to the generation of Ts-cells induced by the malnourished state. Long term renutrition (three weeks) of severely malnourished mice resulted in a complete recovery of all IgA immune responses. Short term renutrition beginning the day of or after oral immunization resulted in an enhanced IgA PFC/spleen response indicating that the mechanism to generate the response recovered before the regulation mechanism. These results suggest that severe protein deprivation leads to a reversible reduction in the IgA immune response to antigens encountered at the intestinal mucosa which is partially due to impaired B-cells and the generation of Ts-cells. |
|---|