Histological analysis of spleen section from REL-AID mouse model. Epifluorescence analysis of 10 μm adjacent spleen cryosections for YFP and tdTomato (TOM) fluorescence together with fluorescent immunolabeling of PNA (A), IgD (B), c-Rel (REL) (C), as well c-Rel isotypic control (Iso) and Ki67 (D) for a REL-AID mouse. All cryosections were counterstained with DAPI. DAPI, YFP, and tdTomato fluorescence were colorized in blue, green, and red, respectively. Fluorescence of PNA, IgD, c-Rel, Iso, and Ki67 markers was colorized in white. For panels A-C, the merged fluorescence for Dapi/YFP/tdTomato/antibody fluorescence is shown in the large image on the left, whereas the small images on the right show the separate fluorescence for the antibody, YFP, and tdTomato (top, middle, and bottom image, respectively). In panels B and C, the red arrow points on a GC predominantly colonized by TOM⁺/YFP^– B cells. (D) shows the fluorescence labeling of the GC pointed by the yellow arrow on panel C. The top images are for c-Rel Iso, c-Rel (REL), and Ki67. Below are images for separate fluorescence of YFP and tdTomato. The bottom image merges Dapi, antibody, YFP, and tdTomato fluorescence. Scale bars are inserted in each merged image.