Researchers report that a gut microbial metabolite, indole, worsens brain injury after stroke by acting on immune cells, with the pathway also tied to poorer outcomes in human patients. The study connects diet-microbiome biology to post-stroke neuroinflammation and identifies an immunologic mechanism that could be targeted to improve recovery. The work, led by researchers at LMU, uses mechanistic experiments to show indole’s role in injury amplification after stroke and links the biology to clinical observations. For translational teams, the metabolite–immune-cell axis offers a concrete handle for therapeutic modulation and biomarker development. The study also raises the likelihood that patient-specific gut microbial profiles may help explain why stroke outcomes vary even under similar clinical conditions, supporting more personalized post-stroke management strategies.