**4. Immunity and fiber in the diet**

The share of CD4+ and CD8+ T-cells in GALT, as well as their in vitro responsiveness to mitogens, were considerably affected by the diet's fiber intake. There was a bigger proportion of CD8+ T-cells in the IEL, lamina propria, and Peyer's patches after consuming the high fermentable fiber diet, as well as a higher proportion of CD4+ T-cells in the mesenteric lymph nodes and peripheral blood except for a higher CD4:CD8 ratio [11, 12].

In the upper gastrointestinal system, prebiotic fiber is neither hydrolyzed nor absorbed, but instead assists as a selective substrate for one or a small number of beneficial colonic bacteria, modifying the gut microbiota. There is significant proof that prebiotic fibers (inulin and oligofructose) boost the percentage of good lactic acid bacteria in the human colon [13].

To yet, the mechanism(s) through which probiotics in the diet alter immune function has primarily been hypothetical. Immune activation via uninterrupted contact of the intestinal microbiota with GALT is one logical method. Small amounts of bacteria can pass through the intestinal epithelial barrier and into Peyer's patches, affecting or contributing to the activation of other immune cells [14]. The production of TNF-α and IL-6 by macrophages, as well as the production of IL-2 and IL-5 by stimulated CD4+ cells, was dramatically boosted by coculture with bifidobacteria [15].
