Photomicrographs of skin biopsy from a patient with acute cutaneous GVHD.

(A) Photomicrograph of adherence assay result showing binding of rat thoracic duct lymphocytes to papillary dermis of skin from patient with acute cutaneous GVHD (methyl green-thionin stain, × 250). The characteristic appearance of arcuate, palisading adherent lymphocytes (dark blue dots) is identified by arrows. This distribution of lymphocytes is typical for binding of cells to underlying vascular structures. (B) Photomicrographs of sequential 8-μm frozen sections of skin biopsy from a patient with acute cutaneous GVHD. Panel Bi shows immunohistochemical stain for CD34 antigen, demonstrating location of endothelial structure. Panel Bii is the adherence assay result, showing PBMCs (blue dots) attaching to dermal papillary structure (methyl green-thionin stain, × 250). Note correlation of CD34 staining with location of adherent lymphocytes (arrows).