Splenic and Intestinal Lymphocyte Proliferation Response in Mice Fed Milk or Yogurt and Challenged withSalmonella Typhimurium

Two groups of 4-5 week old DBA/2J Nii mice were put on either a yogurt-based (n = 33) or a milk-based (n = 32) diet for a period of 4 weeks. At the end of the feeding trial one sub group of mice each from the two dietary groups was sacrificed for assessment of immune response. The remaining mice were challenged intragastrically with 2 x 10(10) live Salmonella typhimurium organisms and continued on their respective diets for 8 days after which they were also sacrificed. The immune response was measured by tritiated thymidine uptake by splenic or intestinal lymphocytes in response to the mitogens concanavalin A (Con A), Phytohaemaggutinin (PHA), and Lipopolysaccharide from Escherichia coli (LPS). Serum Immunoglobulin A levels were also estimated. Feed efficiency, measured as weight gain per unit energy intake, was significantly higher for the yogurt diet than for the milk diet. The mitogenic response of splenic and intestinal lymphocytes in the two groups of unchallenged mice was not different. In the Salmonella-challenged mice the stimulation index (SI) of splenic lymphocytes from yogurt-fed mice (mean +/- SD) was significantly higher (P = 0.001) in response to Con A (24.71 +/- 3.40) than that of milk-fed mice (15.85 +/- 2.09). Further, in these mice the SI of intestinal lymphocytes from yogurt-fed mice was higher than that of milk-fed mice in response to Con A (7.35 +/- 0.61 vs 5.65 +/- 0.78, P = 0.016) and LPS (9.04 +/- 0.93 vs 6.15 +/- 1.32, P = 0.016). Serum IgA levels in Salmonella-challenged mice were significantly higher 8 days after the challenge in the yogurt-fed group than in the milk-fed group (P < 0.001). The experiments indicate an improvement in local gastrointestinal as well as systemic immunity on a yogurt diet as compared to a milk diet.