CD4 and Stroke: In particular, regulatory lymphocyte subpopulations that infiltrate the ischemic brain, including CD4+CD25+ regulatory T cells (CD4+ Tregs) (2, 3) and interleukin 10–positive (IL-10+) regulatory B cells (Bregs) (4), may modulate endogenous protective responses to injury and are therefore being explored as therapeutic approaches for stroke treatment.