Clean living staves off autoimmunity

Autoreactive T cells are harmless until they are prodded into action by exposure to common microbes, according to Yoshitomi and colleagues on page 949. These results may help explain the contribution of environmental factors to human autoimmune diseases like rheumatoid arthritis and diabetes.

While studying an arthritis-prone strain of mouse, Yoshitomi et al. noted that these mice did not develop disease when housed in a microbe-free environment, despite the presence of T cells that could induce arthritis when transferred to nude mice. Only when mice were moved to nonsterile conditions (where they acquired fungal infections) or were injected with β-glucans from fungal cell walls did the telltale symptoms of arthritis appear. Treatment of the mice with antifungal drugs or antibodies that blocked binding of β-glucans to cells reversed this...