Novel helper T cell clones from patients with Crohn's disease

Annunziato F et al. (2007) Phenotypic and functional features of human Th17 cells. J Exp Med 204: 1849–1861

T helper 17 (T_H17) cells are a novel subset of helper T cells, named for their ability to produce interleukin (IL)-17, that are associated with autoimmune diseases in mice. Researchers in Italy have isolated T_H17 cells from the gut of patients with Crohn's disease. A large proportion of the isolated cells produced both IL-17 and interferon-γ, which is normally produced by T_H1 cells, and were therefore termed T_H17/T_H1 cells.

Both T_H17/T_H1 and T_H17 cells facilitated the production by B cells of IgG, IgM and IgA antibodies, but not IgE production. Both cell types had low cytotoxic capability, with poor granzyme A production. T_H17/T_H1 and T_H17 cells selectively expressed IL-23R, CCR6 and the transcription factors RORγt and T-bet (also known as TBX21). Stimulation with IL-12 induced T_H17 cells to produce interferon-γ, increased T-bet expression (both these molecules are associated with T_H1 cells) and downregulated RORγt and IL-17, but these effects could be partly inhibited by IL-23. IL-17-producing cells were detected not only in Crohn's disease tissue, but also in normal gut tissue, peripheral blood and tonsils.

The authors conclude that T_H17 cells display distinct properties of T_H1 and T_H2 cells, but the discovery of T_H17/T_H1 cells, and their modulation by IL-12, suggests a functional or developmental relationship between T_H17 and T_H1 cells.