Dr. Nahrendorf’s group studied mice brains and found that during a stroke, the skull is more likely to supply neutrophils to the injured tissue than the tibia (the shin bone in the leg). In contrast, following a heart attack, the skull and tibia provided similar numbers of neutrophils to the heart, which is far from both the skull or the shinbone. These findings indicate that bone marrow throughout the body does not uniformly contribute immune cells to help injured or infected tissue and suggests that the injured brain and skull bone marrow may “communicate” in some way that results in a direct response from immune cells in the skull bone marrow. According to Francesca Bosetti, Ph.D., program director at the NIH’s National Institute of Neurological Disorders and Stroke (NINDS), which provided funding for the study, “We always thought that immune cells from our arms and legs traveled via blood to damaged brain tissue. These findings suggest that immune cells may instead be taking a shortcut to rapidly arrive at areas of inflammation. Inflammation plays a critical role in many brain disorders and it is possible that the newly described channels may be important in a number of conditions.