New Understanding of Autoimmune Diseases in Mice

Two parts of the immune system play an important role in autoimmune diseases: a subset of T cells called regulatory T (T_reg) cells, which control other immune cells that attack “self” tissue, and a subset of helper T cells called T_H17 cells, which produce the proinflammatory cytokine interleukin-17. In animal models, increasing the number of T_reg cells or decreasing the number of T_H17 cells prevents or reverses autoimmune diseases.

In several new studies, researchers have demonstrated that, in mice, the aryl hydrocarbon receptor (AHR) is a critical switch that causes reciprocal changes in numbers of T_reg and T_H17 cells: When AHR is stimulated by certain cytokines or environmental chemicals, the numbers and activity of T_reg cells go up and T_H…