In the immune system, 'helper' T cells secrete signalling molecules called cytokines to activate other immune cells. A subset of helper cells, CD4+ Th17 cells, can trigger autoimmune diseases such as multiple sclerosis when they release the proinflammatory cytokine IL-17.
Kingston Mills and his colleagues at Trinity College in Dublin have now implicated another type of T cell, the γδ T cell, in autoimmunity. The group showed that γδ T cells are an innate source of IL-17 and other signalling molecules, which they produce when activated by particular cytokines in vitro and in live mice.
The authors found IL-17-secreting γδ T cells in the brains of mice with an autoimmune disease — and that transplanting these alongside CD4+ cells conferred disease on other mice. In vitro, activated γδ T cells amplified the production of IL-17 by CD4+ Th17 cells.