FIGURE 6

PLEXIN B2 is expressed by GC B cells. (a) Flow cytometric analysis of PLEXIN B2 expression (open histograms) or isotype control (shaded histograms) on splenocytes from immunized mice gated on resting B cells (top panel) and GC B cells (bottom panel) following the strategy shown in Figure 5a. (b) Photomicrographs of serial spleen sections from immunized mice showing GC stained in blue for PNA (top) and PLEXIN B2 (bottom), and in brown for IgD. (c) Western blots from lysates of sorted resting B cells and GC B cells probed with anti-PLEXIN B2 serum. -Actin was used as a loading control. (d) Flow cytometric analysis of PLEXIN B2 expression on splenocytes from SW_HEL mice 5 days after adoptive transfer into congenic CD45.1 mice and immunization with HEL² -SRBC. Gates for extrafollicular CD45.2^low HEL-binding plasma cells (PC) and CD45.2^high HEL-binding GC B cells are shown in the dot blot (left). (e) Histograms show flow cytometric analysis of PLEXIN B2 expression after stimulation of purified B cells for 6 days under the conditions indicated. The expression of PLEXIN B2 on resting B and GC cells was examined in the same experiment. Shaded histograms indicate staining with an isotype control antibody. These results are representative from at least two independent experiments. GC, germinal centre; Ig, immunoglobin; HEL, hen egg lysozyme; SRBC, sheep red blood cells.