Figure 2. TNF--positive periodontal ligament fibroblasts in rats. Staining with isotype control immunoglobulin showing absence of reactivity (A). Few TNF--positive fibroblasts with brown-stained cytoplasm were found in the Control group (B). More TNF--positive fibroblasts were observed in the Combination group (C,C'). Fibroblast counts (D) and ratios of TNF--positive fibroblasts to total fibroblasts (E) for the 4 experimental groups (mean ± SD). AB, alveolar bone; CM, cementum. Scale bar = 25 µm. ^ap < 0.05, compared with the Control group. ^bp < 0.05, compared with the Periodontitis group.