Figure 1. Identification of Tr-cell-related markers in periodontitis lesions. Immunohistochemical double-staining for CD25 (blue)/CD4 (brown) (A), CTLA-4 (blue)/CD4 (brown) (B), and CTLA-4 (blue)/CD25 (brown) (C), and subsequent immunofluorescent staining by FITC-conjugated CD4 on the same section (D). Single-positive cells and double-positive cells are indicated by open arrowhead and closed arrowhead, respectively (A,B). Photographs of the same areas (C,D) showed CD4⁺CD25⁺CTLA-4⁺ triple-positive cells (closed arrowhead) and CD4⁺CD25⁺CTLA-4^– double-positive cells (open arrowhead) in periodontitis lesions.