Infiltrating T cells express markers of cytotoxicity, type 1 cytokine polarization, and effector-memory phenotype. (A-D) Infiltrating T cells express CD45RO, a surface marker of the effector-memory T cells. Note predominance of the CD8 cells in the infiltrate. (E) CD68 myeloid cells are also overrepresented in oral cGVHD. CD8 cells express granzyme B (F) and Tia-1 (G) in the cytoplasm and are closely associated with the apoptotic cells (green, G). Note polarization of the cytotoxic granule (red) within the CD8 cell (cyan) in the direction of the apoptotic keratinocyte (green) shown by arrow. (B) Close-up of the same image with the arrows pointing to the granzyme B granules. (H,I) T-bet expression by the infiltrating T cells. (J-L) CD8 (n = 8, n = 16, and n = 12 for control, mild, and severe groups, respectively) and CD68 cells (n = 8, n = 15, and n = 10 for control, mild, and severe groups, respectively) are particularly prominent in severe disease (*P < .05; error bars represent SEM).