CD4 and medical procedure: In a study examining the role of CD4 T-cells in stroke, Zhang et al. (2018) induced a transient middle cerebral artery occlusion (tMCAO) in major histocompatibility complex (MHC) II knockout mice and observed a smaller infarct volume as compared to the wildtype control, supporting the idea that the presence of CD4 T-cells is detrimental in stroke.