Co-localization of PE binding and GL7 staining B cells in situ. Sections of draining LN were stained with PE, followed by antibodies specific for GL7 (green), IgD (purple), Thy1.2 (blue), or PE (red). LN sections were from an unimmunized mouse (A) or from mice 4 d (B–E) or 14 d (G) after injection. Arrows in B show PE⁺ GL7⁺ cells (yellow) present at the T/B border. A close-up of a 4 d T/B border region shows the overlay of all colors (C), PE only (D), or GL7 only (E) with an arrow pointing to a double staining GL7⁺ PE⁺ cell. (F) The graph shows the percentage of the PE⁺ cells that were in the follicles or at the T/B border in sections of draining LN taken from PE/CFA-injected mice on day 4. The percentage of GL7⁺ PE⁺ cells is depicted with an empty bar and the percentage of GL7⁻ PE⁺ cells is depicted with a filled bar. The T/B border was identified as a swath, 8–10 cells wide, where the IgD and Thy1.2 staining were mixed. The T cell areas, medullary chords, or any region not clearly resolved as follicle or T/B border were excluded from the analysis. 84 PE⁺ cells were counted in sections taken from 10 LNs obtained from five individual mice.