T cell differentiation

Germ-free mice typically possess a limited number of intestinal T helper (Th)17 cells and Helios-negative peripheral (p) Treg cells. However, when these mice are colonized with segmented filamentous bacteria (SFB), there is a differentiation into T helper 17 cell (Th17). Similarly, colonization with a consortium of spore-forming Clostridium species leads to the differentiation of peripheral Treg cells (i.e., RAR-related Orphan Receptor Gamma/T (ROR-gamma/t) Isoform 2 (NR1F3)t+ Foxp3+ Colonic Treg cells)
Ivanov et al. 2009
Atarashi et al. 2011

see also:
Gut microbiota & RAR-related Orphan Receptor Gamma/T (ROR-gamma/t) Isoform 2 (NR1F3)t + Foxp3 + Colonic Treg cells
Gut microbiota & T helper 17 cell (Th17)