Migration and proliferation of infiltrating T cells in oral cGVHD. Infiltrating T cells (A) express the chemokine receptor CXCR3 (B). (C) Overlay of CD3 and CXCR3. (D) Increased production of the CXCR3 ligand MIG (CXCL9) by the keratinocytes (arrow) and infiltrating cells in a patient with severe oral GVHD. (E) Control patient without oral cGVHD symptoms with minimal MIG expression by the keratinocytes and endothelial cells (arrow). (F) Negative isotype staining control. (G) Enlarged image demonstrating MIG expression by CD68⁺ cells (large arrow), as well as CD68⁻ cells (small arrow). Infiltrating T cells proliferate in the oral mucosa affected by cGVHD. (H) Severe oral cGVHD; close-up image showing nuclear expression of proliferation marker Ki-67 in a CD8 cell (large arrow). Basal keratinocytes (small arrow) proliferate constitutively. (I) Lack of proliferating T cells in a patient without clinical oral cGVHD. (J-L) Severe cGVHD (n = 12) is characterized by increased number and percentage of proliferating T cells compared with patients with mild (n = 16) or no (n = 8) oral cGVHD (*P < .05; error bars represent SEM).