Immunofluorescent imaging of infiltration of human CD3⁺, CD4⁺, and CD8⁺ T lymphocytes in the liver of a mouse with acute X-GVHD. Immunofluorescent imaging was performed of the lungs, liver, and spleen of 5 mice with acute X-GVHD in the third experiment. Infiltration of human T lymphocytes, indicated by green fluorescence, was present at day 16 in all organs. An example is shown of infiltration of human CD3⁺, CD4⁺, and CD8⁺ T lymphocytes in the liver of one mouse compared with a control slide. Original magnification, × 10.