Lactobacillus reuteri induces gut intraepithelial CD4 ⁺ CD8αα ⁺ T cells

The small intestine contains CD4+CD8αα+ double-positive intraepithelial lymphocytes (DP IELs), which originate from intestinal CD4+ T cells through down-regulation of the transcription factor Thpok and have regulatory functions. DP IELs are absent in germ-free mice, which suggests that their differentiation depends on microbial factors. We found that DP IEL numbers in mice varied in different vivaria, correlating with the presence of...