Antigen-specific Foxp3+ Tregs control tolerance to gut pathobiont H. hepaticus

Helicobacter hepaticus, H. hepaticus, is an opportunist commensal, a pathobiont, that causes gut inflammation in IL-10 deficient but not in WT mice. A New study in journal Nature from Dan Littman's lab tried to understand basis for such dual nature of host response to H. hepaticus.

The authors have generated transgenic T cells specific for H. hepaticus-unique protein, HH_1713. Next, the authors co-transferred H. hepaticus-specific T cells (HH7-2tg cells) alongside with segmented filamentous bacteria, SFB-specific T cells (7B8tg cells) into WT mice exposed to H. hepaticus. Interestingly, HH7-2tg cells mostly differentiated into RORγt+ Foxp3+ Tregs while 7B8tg cells mostly differentiated into Th17 cells, as observed in earlier studies.

However, similar transfer of H. hepaticus-specific T cells into IL-10KO mice exposed to H. hepaticus mostly yielded inflammatory T cells (Th17 and Th1 cells).

It appears that transcription factor c-MAF control differentiation of H. hepaticus-specific T cells into RORγt+ Foxp3+ Tregs and its deficiency recapitulates H. hepaticus-specific T cells differentiation into inflammatory T helper cells observed in IL-10KO hosts when exposed to H. hepaticus.

In summary, this study indicates that in WT mice harbor H. hepaticus specific Foxp3+ T cells that keep tolerance to H. hepaticus. These induced Foxp3+ T cells are probably generated (or expand) by chain reaction orchestrated by existed antigen-specific natural Tregs since induced Tregs don't develop efficiently when transferred into RAG KO hosts lacking natural Tregs. IL-10 or c-MAF deficiency could alter overall microbiota composition (unrelated to H. hepaticus) and drive shift from Treg program into inflammatory pathway.

posted by David Usharauli