CD19 and Stroke: Intravenous administration of EXO‐PD‐L1‐HGF to the mice with stroke significantly reduced the percentages of CD11c+CD80+ and CD11c+CD86+ (activated dendritic cells), CD3+CD8+IFN‐γ+ (cytotoxic T cells), CD3–NK1.1+ (natural killer cells), and CD11b+CD80+ cells (M1 macrophage cells) (Figure 8b,c), but enhanced the percentages of CD19+IL‐10+ (regulatory B cells), CD8+CD122+IL‐10+ (Treg cells), and CD11b+CD206+F4/80+ cells (M2 macrophage cells) (Figure 8d,e) in the ischemic hemisphere and spleen, as compared with that in the EXO‐treated and control groups.