Dietary plasma protein affects the immune response of weaned rats challenged with S. aureus Superantigen B

Abstract

The aim of this study was to determine the potential modulatory effects of diets supplemented with spray-dried animal plasma (SDAP) or immunoglobulin concentrates (IC) on the immune response of rats challenged with Staphylococcus aureus enterotoxin B (SEB). Lewis rats were fed diets containing 80 g of SDAP/kg diet, 22.7 g of IC/kg diet, or milk proteins (Control diet) from postnatal d 21 (weaning) for 14 d. On d 30 and 33, rats were given SEB (0.5 mg/kg body weight; i.p.). Organized gut-associated lymphoid tissue (GALT) populations, intestinal secretion, mucosal and serum immunoglobulin concentrations, and neutrophil infiltration were studied. On d 35, blood was collected under anesthesia and samples of intestinal mucosa, Peyer's patches, mesenteric lymph nodes (MLN), and spleen were taken. SEB increased the water content of feces, which was prevented by diets containing either SDAP (P < 0.002) or IC (P < 0.001), indicating that plasma protein-supplemented diets can reverse the SEB-induced secretory response. In Peyer's patches, the diet containing SDAP partially prevented the SEB-induced increase in T lymphocytes (P < 0.1) and reduced the percentage of activated T helper cells (P < 0.05). In MLN, activated T lymphocytes were increased by SEB but they were not affected by diet. No effects of SEB or dietary supplementation on mucosal IgA and serum IgA and IgG were observed. The effects of SDAP supplementation on the lymphocyte populations of GALT in rats challenged with SEB support the view that SDAP can modulate the immune response and suggest that plasma protein supplementation can prevent GALT from possible activation by luminal bacterial superantigens.

FIGURE 1

Food intake (A) and body weight (B) of Lewis rats fed a control diet (Healthy) and rats challenged with SEB (SEB) and supplemented with SDAP (SEB-SDAP) and with IC (SEB-IC) for 14 d. Results are expressed as means ± SEM, n = 7–10. In most cases, bars were smaller than symbols.

FIGURE 2

Changes in the water content in feces (expressed as % of wet weight) in rats challenged with a double dose of SEB (50 μg i.p. at d 30 and 33) and fed supplements of plasma (SEB-SDAP) and immunoglobulin concentrate (SEB-IC). Results are expressed as means ± SEM, n = 7–10. *Different from Healthy rats, P < 0.05. Means for rats challenged with SEB without a common letter differ, P < 0.05.

FIGURE 3

Lymphocyte populations in Peyer's patches from Healthy rats and rats challenged with SEB and fed diets supplemented with SDAP or IC. CD45RA⁺ (as B lymphocytes), CD3⁺ (as T lymphocytes), CD4⁺ (as helper T lymphocytes), CD8⁺ (as suppressor/cytotoxic T lymphocytes), NK (as natural killer cells), CD25⁺CD3⁺ (as total activated T lymphocytes), CD25⁺/CD4⁺ (as the fraction of activated T helper lymphocytes), CD25⁺/CD8⁺ (as the fraction of activated suppressor/cytotoxic T lymphocytes), and γδ-T lymphocytes as percentages with respect to the total number of lymphocytes. Results are expressed as means ± SEM, n = 8–10. *Different from Healthy rats, P < 0.05. Means for rats challenged with SEB without a common letter differ, P < 0.05.