Effects of dietary fermentable material on innate and adaptive immune measures in male and female rats under resting and immunized conditions

Abstract

Sex-based differences in immune parameters are well recognized, and recent evidence suggests differences in microbiota composition between sexes, necessitating assessment of effects of dietary fermentable material (DFM) in both males and females. Effects of consumption of DFM of differing composition (Wheat Bran (WB), Oat Bran (OB), Resistant Starch (RS), Fructooligosaccharides (FOS)) on the immune system were compared under resting and immunized conditions between sexes. The gut microbiota composition and short chain fatty acid profiles differed between rats fed different DFM and also differed between sexes following FOS consumption. Immune parameters were analyzed for the effect of diet, differences between sexes or interactions (diet x sex), to detect the effect of DFM on male and female rats. The kinetics of primary (Day 0, 5, 10, 15) and secondary antibody responses (Day 21) were measured following immunization with a T cell-dependent antigen, Keyhole Limpet Hemocyanin (KLH). Under resting conditions, male rats had more FoxP3+ Treg cells in the mesenteric lymph node (MLN) and spleen than did females. Levels of the regulatory cytokine TGF-β1 also increased in the MLN in a DFM-dependent manner. In contrast, percentages of MLN and splenic CD68+ macrophages and levels of gut tissue IL-10 were higher in females than males. These results suggest immune regulation at the mucosal level is controlled in a differential manner between sexes and was affected by DFM intake only in males. At the systemic level, DFM intake delayed the primary anti-KLH IgG antibody response kinetics in male (control>>WB>OB>RS>FOS) and female (control> FOS>WB>RS>OB) rats. The secondary anti-KLH IgG response in control-fed males was 10-fold higher than in control-fed females. DFM intake in males significantly decreased anti-KLH IgG levels relative to control-fed males. Collectively, these findings demonstrate DFM consumption in males potentially induces systemic immune regulation leading to a delayed response to immune challenge, an effect that was not observed in females.