OT-1 effector motility in GVHD skin lesions. One hundred twenty-nine mice were irradiated and transplanted with B6 CD11c-YFP BM and CFP⁺ B6 CD4 and CD8 cells. On day 28, mice were injected with DsRed⁺ OT-1 effectors and imaged by 2PIM the following day. Each column shows images from a single mouse. In images in the second row, the YFP channel is masked to better visualize the dsRed+ OT-1 (supplemental Videos 15-20).