IL17A and stroke disorder: Antibiotic-induced alterations in the intestinal flora reduced ischemic brain injury in mice, an effect transmissible by fecal transplants. Intestinal dysbiosis altered immune homeostasis in the small intestine, leading to an increase in regulatory T cells and a reduction in interleukin (IL)-17-positive γδ T cells through altered dendritic cell activity. Dysbiosis suppressed trafficking of effector T cells from the gut to the leptomeninges after stroke.