FEEDING HEATED SOYBEAN FLOUR INCREASES THE DENSITY OF B-LYMPHOCYTES AND T-LYMPHOCYTES IN THE SMALL-INTESTINE OF CALVES

The effect of dietary antigens on the gut morphology and density of im mune cells was studied in preruminant calves fed milk substitutes cont aining skim milk powder (SMP), non-antigenic hydrolysed soya protein i solate (HSPI) or antigenic heated soyabean flour (HSF) as their main p rotein source for 3 months. The height and perimeter of proximal jejun um villi were highest in the calves fed SMP and lowest in those fed HS F (P < 0.05). In contrast, the crypt depth and perimeter were apparent ly not influenced by the dietary treatments studied. This morphologica l alteration was associated with a dramatic infiltration of the lamina propria by B and T lymphocytes in the calves fed HSF (P < 0.01). Incr eased B cell density was essentially accounted for by IgA-, IgG1- and IgG2-bearing cells, The density of CD2-positive T lymphocytes increase d (P < 0.01) in the jejunal lamina propria of HSF calves, involving he lper (CD4+) and suppressor-cytotoxic (CD8+) T cell subsets. The densit y of gamma-delta (WC1+) T cells also increased (P < 0.01). The major c hange concomitantly observed in the villus epithelium was an increased density of CD8+ cells (P < 0.05) and WC1+ cells (P < 0.01).