We investigated the effect of Lactobacillus crispatus KT-11 (KT-11) on intestinal immune systems in C3H/HeN mice. The level of intestinal total immunoglobulin (Ig) A was significantly higher in mice given KT-11 than in mice not given KT-11. Gene expression relating to antibody production and innate immune response increased more than 2-fold in the former compared with the later. Moreover, the number of IL-6⁺CD11b⁺ cells was significantly higher in Peyer's patch cells cultured with KT-11 than in those cultured without KT-11, although the number of CD4⁺ cells and the cell ratio of CD4⁺/CD8⁺ were remarkably lower in the culture with KT-11. These results indicate that KT-11 enhances intestinal IgA production and innate immune response in C3H/HeN mice.