SPLENIC AND INTESTINAL LYMPHOCYTE-PROLIFERATION RESPONSE IN MICE FED MILK OR YOGURT AND CHALLENGED WITH SALMONELLA-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 t wo dietary groups was sacrificed for assessment of immune response. Th e remaining mice were challenged intragastrically with 2 x 10(10) live Salmonella typhimurium organisms and continued on their respective di ets for 8 days after which they were also sacrificed. The immune respo nse was measured by tritiated thymidine uptake by splenic or intestina l lymphocytes in response to the mitogens concanavalin A (Con A), Phyt ohaemaggutinin (PHA), and Lipopolysaccharide from Escherichia coli (LP S). Serum Immunoglobulin A levels were also estimated. Feed efficiency , measured as weight gain per unit energy intake, was significantly hi gher for the yogurt diet than for the milk diet. The mitogenic respons e of splenic and intestinal lymphocytes in the two groups of unchallen ged mice was not different. In the Salmonella-challenged mice the stim ulation index (SI) of splenic lymphocytes from yogurt-fed mice (mean /- SD) was significantly higher (P = 0.001) in response to Con A (24.7 1 +/- 3.40) than that of milk-fed mice (15.85 +/- 2.09). Further, in t hese mice the SI of intestinal lymphocytes from yogurt-fed mice was hi gher 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 IEA levels in Salmonella-challenged mice were signific antly higher 8 days after the challenge in the yogurt-fed group than i n the milk-fed group (P < 0.001). The experiments indicate an improvem ent in local gastrointestinal as well as systemic immunity on a yogurt diet as compared to a milk diet.