Enhanced antigen-specific delayed-type hypersensitivity and immunoglobulinG2b responses after oral administration of viable Lactobacillus casei YIT9029 in Wister and Brown Norway rats

In this study, the effects of orally administered viable Lactobacillus case i Shirota strain YIT9029 on the immunity parameters of Wistar and Brown Nor way rats were examined. For this purpose, we used the Trichinella spiralis host resistance model, Two weeks before and during T. spiralis infection, r ats were fed 10(9) viable L. casei bacteria 5 days per week The T. spiralis -specific delayed-type hypersensitivity (DTH) response was significantly en hanced in both Wistar and Brown Norway rats given L. casei, In both rat str ains fed L, casei, serum T. spiralis-specific immunoglobulin G2b (IgG2b) co ncentrations were also significantly increased. In the model, no significan t effects of L, casei on larval counts or inflammatory reactions in the ton gue musculature, body weights, or lymphoid organ weights were observed, Ser um specific antibody responses, other than IgG2b, were not changed by feedi ng oft. casei. In contrast to L. casei, it was shown that orally administer ed Bifidobacterium breve or Bifidobacterium bifidum had no influence on the measured infection and immunity indices in the rat infection model. Since the rat DTH response is considered to be a manifestation of Th1 cell-mediat ed immunity and the IgG2b isotype has been associated with Th1 activity, it was concluded that Th1 cells could play an active role in the immunomodula tory effects of orally administered L. casei, Furthermore, our data do not indicate that the effect of oral supplementation with L, casei is dependent on the genetic background of the host.