Regional variations in the distributions of small intestinal intraepithelial lymphocytes (IELs) in outbred laboratory mice (Mus musculus domesticus) and the inbred strain of mice established from Japanese fancy mice (Mus musculus molossinus)

[Comparison of the Susceptibility to Tetrodotoxin in ddY Strain Mice from Different Breeder Companies]

The mouse bioassay for tetrodotoxin has been used in Japan and ddY strain mice are designated to be used in the assay. ddY strain is a closed-colony outbred mouse strain, originally from the National Institute of Health, however, the ddY mouse stocks of 3 breeders were divided 30 or more years ago. In this study, we investigated the differences in susceptibility to tetrodotoxin in ddY strain mice from 3 different breeders in Japan. No statistically significant differences were found among the ddY strain mice of 3 breeders, however, the coefficient of variation were different among the breeders. The results using the mice from one breeder were much stable compared with those using the mice from other 2 breeders.

Age-dependent changes in intraepithelial lymphocytes (IELs) of the small intestine, cecum, and colon from young adult to aged mice

We previously reported the regional differences in the IELs present in the proximal (P), middle (M), and distal (D) parts of the small intestine, cecum (Ce), and colon (Co) of mice. In this study, we investigated the age-dependent changes in the regional differences of IELs from young adult to aged mice. In this experiment, 3-, 6-, 12-, 18-, and 24-month-old mice were examined. IELs were separately isolated from 5 parts of the intestines and analyzed by flow cytometry. Regional differences in the number and phenotype of IELs showed the same trends in all age groups. The number of IELs was highest in 6-month-old mice and then gradually decreased with age. As to IEL subsets, age-related changes were not seen except for a few subsets among the age groups. We conclude that age-related decreases in IELs in mouse small intestine may be one of the aging phenomena of the intestinal immune system. Such age-related decreases in IELs may be concerned with the increased liability to intestinal infections in the elderly.

Differences in intraepithelial lymphocytes in the proximal, middle, distal parts of small intestine, cecum, and colon of mice

We have previously reported the regional differences in the intraepithelial lymphocytes (IELs) present in the small intestine of mice. In this study, we further investigated these differences on the basis of our previous findings and studied the entire intestine, including the cecum and colon. Most of the significant differences in phenotypic compositions were found between the small and large intestines, although some differences were found among the different parts of the small and large intestines. In particular, the composition of the subsets in alphabeta T cells and gammadelta T cells clearly differed between the small and large intestines. For example, in alphabeta T cells, the percentages of double negative (DN) and CD8alphaalpha(+) cells were higher in the large intestine, that of CD8alphabeta(+) cells was higher in the small intestine, and those of CD4(+) and CD4(+) CD8alphaalpha(+) double positive (DP) cells were higher in the distal part of the small intestine. In gammadelta T cells, the percentage of CD8alphaalpha(+) cells was higher in the small intestine and that of DN cells was higher in the large intestine. These results indicate that the differences between IELs in the small and large intestines are discontinuous.