Dietary plasma proteins modulate the immune response of diffuse gut-associated lymphoid tissue in rats challenged with Staphylococcus aureus enterotoxin B.

We have previously shown that plasma protein supplementation prevents the activation of lymphocyte populations of Peyer's patches and mesenteric lymph nodes, which is known as organized gut-associated lymphoid tissue (GALT). Here, we examined the effects of spray-dried plasma proteins (SDAP) and Ig concentrate (IgC) supplements on lamina propria and intraepithelial lymphocytes (diffuse GALT) in a model of mild intestinal inflammation induced by the intraperitoneal administration of Staphylococcus aureus enterotoxin B (SEB). Wistar-Lewis rats were fed diets supplemented with SDAP (8% wt:wt), IgC (1.5% wt:wt), or bovine milk proteins (control diet) from weaning (d 21) to d 34 after birth. On d 30 and 33, rats were given SEB (0.5 mg/kg body weight) or PBS (control). Experimental groups were designated control, SEB, SEB-SDAP, and SEB-IgC. Lymphocyte populations were analyzed by immunohistochemistry. In lamina propria, SEB increased the cytotoxic lymphocyte populations of T-gammadelta cells (38%; P < 0.001) and natural killer cells (59%; P < 0.05) and the number of activated T lymphocytes (148%; P < 0.001). Both SDAP and IgC decreased the effects of SEB on these lymphocyte subsets (P < 0.05). In the epithelium, SEB induced a 117% increase in intraepithelial-activated lymphocytes that was reduced by SDAP supplementation (P < 0.01). The effects of plasma supplements on intestinal lymphocyte populations suggest that oral plasma proteins can modulate the degree of activation of diffuse GALT.