Traumatic brain injuries (TBIs) affect millions of Americans annually, leading to a range of cognitive, behavioral, and physical impairments. Researchers at Gladstone Institutes have uncovered a key molecular mechanism that triggers neurodegeneration after TBI: the protein fibrin. Fibrin activates immune cells, releasing toxins that damage neurons. The team developed a genetic tool to block fibrin’s harmful effects without impairing its blood-clotting abilities. Their findings suggest that targeting fibrin could lead to new therapies for TBI and other neurological diseases.