Figure 1. A B-lymphocyte response to stroke occurs in C57BL/6J mice. A, Schematic diagram of a mouse coronal brain section following DH stroke, with the stroke core shaded in gray and a red box to indicate the region immunostained in B–D, and used for flow in E. B, Immunostaining for B220 (B-lymphocytes) shows that B cells are present in the lesion 7 weeks following DH stroke in C57BL/6J mice. Scale bar, 250 μm. C, Fluorescent immunostaining for the B-lymphocyte marker B220 (red) and the dendritic cell marker CD11c (green) shows that B cells are still present in the lesion 12 weeks following stroke and are juxtaposed to cells immunostaining for CD11c. Scale bar, 25 μm. Images are representative of 10 mice that underwent stroke. D, Fluorescent immunostaining for the B-lymphocyte marker B220 (magenta) and the T-cell marker CD3 (green) reveals that B cells and T cells are compartmentalized 7 weeks following DH stroke. Scale bar, 100 μm. E, Flow cytometry revealed that 9% of CD19+ B-lymphocytes present in the stroke lesion were CD19+ CD138+ plasma cells (n = 10 pooled stroke lesions). F, G, Representative images of IgG immunostaining in the hippocampus 7 weeks following stroke or sham surgery (n = 10). H, Determination of antibody isotypes present in the cortex and hippocampus 7 weeks following stroke or sham surgery (stroke n = 7; sham n = 3). *p < 0.05, compared with sham. Error bars indicate SD. I, J, Immunostaining for the B-cell marker B220 4 weeks after stroke in two additional stroke models performed in C57BL/6J mice: MCAO (I) and photothrombotic stroke (PT stroke) (J). Scale bars, 500 and 100 μm (lower and higher magnifications, respectively).