<i>Lactobacillus reuteri</i> induces gut intraepithelial CD4 ⁺ CD8αα ⁺ T cells

TLDR

Double‑positive intraepithelial lymphocytes (DP IELs) are a recently discovered intestinal T cell type involved in oral tolerance, yet their development mechanisms remain unclear and they are absent in germ‑free mice. Lactobacillus reuteri induces DP IELs by producing a tryptophan derivative that drives precursor differentiation, rather than directly stimulating the immune system, highlighting the interplay between commensals, diet, and gut health. Cervantes‑Barragan et al.

Abstract

Tolerogenic T cells need probiotics CD4 + CD8αα + double-positive intraepithelial lymphocytes (DP IELs) are a recently discovered class of intestinal T cells believed to take part in a variety of immune responses, including oral tolerance. These cells are absent in germ-free mice, but the mechanisms driving their development are unclear. Cervantes-Barragan et al. found that a particular species of probiotic bacteria, Lactobacillus reuteri , induces DP IELs. This does not occur by stimulating the immune system directly. Instead, L. reuteri generates a specific derivative of dietary tryptophan that promotes differentiation of DP IEL precursors. These findings underscore the delicate interplay between benign bacteria, diet, and gut health. Science , this issue p. 806