Fig. 4.

IgM⁺ and IgD⁺ B cells are localized within the meninges and perivascular space. Sagittal brain sections were stained with the indicated combinations of anti-B220, IgD, IgM, IgG, and laminin mAb to identify B cell localization to meninges and blood vessels and relative to basement membranes at day 7,14, and 21 p.i. (dpi) (A) B220⁺ (red) B cell localization relative to laminin⁺ (green) structures. Arrows indicate isolated B cells emerging at parenchymal sites at day 14 p.i. (B) IgD⁺ (red) B cells confined to the perivascular space. (C) IgM⁺ (red) cells present within the laminin⁺ subpial meningeal space. (D) Localization of both IgD⁺IgM⁺ and IgM⁺IgD⁻ B cells within the CNS at d14 p.i. (E) IgG⁺ (red) B cells and laminin (green) at day 21 p.i. within the CNS. Representative images shown are z stack projected compilations from 2 independent experiments with 3 mice per experiment. (F) Percent distribution of isotype-unswitched (IgM⁺) and isotype-switched (IgG+) B cells at day 14 and 21 p.i. For quantification, 6–8 Z stacks representing 2–3 animals per time point were counted manually for IgM⁺ or IgG⁺ B cells within the parenchyma or perivascular/meningeal space, defined by laminin staining. Data are expressed as the mean percentage ± SEM. Scale bars = 50 μm (A, E) and 20 μm (B–D). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)