Antigen-Presenting Human ?? T Cells Promote Intestinal CD4+ T Cell Expression of IL-22 and Mucosal Release of Calprotectin.

ABSTRACT: The cytokine IL-22 plays a critical role in mucosal barrier defense, but the mechanisms that promote IL-22 expression in the human intestine remain poorly understood. As human microbe-responsive V?9/V?2 T cells are abundant in the gut and recognize microbiota-associated metabolites, we assessed their potential to induce IL-22 expression by intestinal CD4+ T cells. V?9/V?2 T cells with characteristics of APCs were generated from human blood and intestinal organ cultures, then cocultured with naive and memory CD4+ T cells obtained from human blood or the colon. The potency of blood and intestinal ?? T-APCs was compared with that of monocytes and dendritic cells, by assessing CD4+ T cell phenotypes and proliferation as well as cytokine and transcription factor profiles. V?9/V?2 T cells in human blood, colon, and terminal ileum acquired APC functions upon microbial activation in the presence of microenvironmental signals including IL-15, and were capable of polarizing both blood and colonic CD4+ T cells toward distinct effector fates. Unlike monocytes or dendritic cells, gut-homing ?? T-APCs employed an IL-6 independent mechanism to stimulate CD4+ T cell expression of IL-22 without upregulating IL-17. In human intestinal organ cultures, microbial activation of V?9/V?2 T cells promoted mucosal secretion of IL-22 and ICOSL/TNF-?-dependent release of the IL-22 inducible antimicrobial protein calprotectin without modulating IL-17 expression. In conclusion, human ?? T-APCs stimulate CD4+ T cell responses distinct from those induced by myeloid APCs to promote local barrier defense via mucosal release of IL-22 and calprotectin. Targeting of ?? T-APC functions may lead to the development of novel gut-directed immunotherapies and vaccines.

SUBMITTER: Tyler CJ 

PROVIDER: S-EPMC5392732 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature