Alteration of mucosal immunity after long-term ingestion of an elemental diet in rats

The effects of an elemental diet on lymphocyte transport in intestinal lymph and immune responses of gut-associated lymphoid tissue were investigated in rats. The control animals were fed a conventional diet. After 4 week of feeding, the total calorie intake and body weight gain showed no differences between the two groups. The number and total area of Peyer's patches and the ratio of height of villi to height of crypt showed no significant differences between the two groups. The rate of lymph flow in intestinal lymphatics showed no significant change in treated animals compared with the control rats. However, an elemental diet induced a significant decrease in lymphocyte flux in intestinal lymphatics compared with that in control rats. Lymphocyte subsets in intestinal lymph revealed a significant decrease in CD3-positive cells, especially CD4-positive cells in the elemental diet-treated group. A significant decrease in the number of immunoglobulin A-containing cells and a decreased CD4/CD8 ratio in T-cell subsets were observed in the lamina propria of ileal mucosa in the elemental diet-treated group by morphometric analysis in the immunohistochemical study. Specific antibody-secreting cells in intestinal lymph were also investigated after rats were intraduodenally primed with cholera toxin and challenged with the same toxin after an interval of 2 weeks. No significant difference was seen between the two groups in any of the numbers of anti-cholera toxin immunoglobulin-secreting cells in any immunoglobulin A, immunoglobulin G, or immunoglobulin M class as determined by the enzyme-linked immunospot assay.(ABSTRACT TRUNCATED AT 250 WORDS)