Fig 1: The source of CXCL13 production in TLS shifts to CD21+ FDC with the maturation of TLS.(A) Representative images of early TLS. Upper panels show CXCL13 (RNA ISH, Fast RED) and lower panels show FDC (CD21 IHC, DAB). (B) Representative images of follicle-formed TLS. The middle panel is the same case as TLS(2), found in Figure 2A, which shows one of the most typical Follicle-formed TLS. The presence of CD21+ FDC is shown in the bottom panel. (C) Fluorescence double staining of CXCL13 (red) and CD4 (green), CXCL13 (red) and CD8 (white), and CXCL13 (red) and CD21 (light blue) in representative early TLS and follicle-formed TLS. The same Early TLS shown in Figure 3A was used to show the cell source of CXCL13 expression. Nuclei are stained with DAPI (blue). Scale bar: 100 µm. Colocalization of CXCL13 with CD4, CD8, or CD21 is shown in the bar graph as the relative positive ratio quantified using BZ-H4C/hybrid cell count software.