Supplementation of diets with plasma protein has been shown to prevent the activation of lymphocyte populations of Peyer's patches and mesenteric lymph nodes(Reference Pérez-Bosque, Pelegrí and Vicario1) and improve the intestinal epithelial barrier function in a rat model of intestinal inflammation(Reference Pérez-Bosque, Amat, Polo, Campbell, Crenshaw, Russell and Moretó2). The present study investigated the effects of porcine plasma proteins (SDAP) and Ig concentrate (IC) supplements on diffuse gut-associated lymphoid tissue in a model of mild intestinal inflammation. The different populations of lamina propria and intraepithelial lymphocytes, as well as mucosal expression of cytokines (interferon-γ (IFN-γ), TNFα, IL-6 and IL-10) and pro-inflammatory mediators (inducible NO synthase (iNOS) and leukotriene B4 (LTB4)), were investigated. Wistar-Lewis rats were fed diets supplemented with SDAP (80 g/kg; n 9), IC (15 g/kg; n 9) or milk proteins (control die; n 9) from weaning (day 21) to day 33 or 34 after birth. On days 30 and 33 rats were administered S. aureus enterotoxin B (SEB; 0.5 mg/kg). Experimental groups were control, SEB, SEB-SDAP and SEB-IC. Lymphocyte populations were analysed by immunohistochemistry on day 34 (i.e. 24 h after SEB administration). The markers used were: CD3 (T lymphocytes), CD25 (activated T lymphocytes), CD4 (T-helper lymphocytes), CD8 (T-suppressor/cytotoxic lymphocytes), TCRγδ (T-γδ lymphocytes) and NKPR1A (NK cells). Cytokines were determined by a cytometric bead array assay, LTB4 by commercial ELISA and iNOS by real-time PCR in mucosal homogenates, all at 6 h after SEB administration.
In both lamina propria and epithelium compartments SEB increased the lymphocyte cytotoxic populations (T-γδ 40% and 70%; NK cells 60% and 75% respectively, all P<0.05) and doubled the number of activated T lymphocytes (P<0.001). Both SDAP and IC prevented the SEB effects on the lamina propria, while in the epithelium only SDAP reduced the extent of T-cell activation (P<0.05). SEB increased mucosal iNOS expression by 28% (P<0.05) and both plasma protein supplements prevented SEB effects on iNOS expression in the intestinal mucosa (both P<0.05).
In the mucosa SEB doubled IFN-γ and LTB4 concentrations and increased TNFα and IL-6 concentrations by 20–30%; P<0.05). SDAP partially prevented these effects on IFN-γ, IL-6 and LTB4 (P<0.05). IC was also effective in reducing the expression of TNFα and LTB4 in the mucosa (P<0.05). It is concluded that dietary supplementation with plasma proteins can attenuate the intestinal inflammatory effects induced by SEB.
