Expression of KDR on T cells within human cardiac and renal allografts. (A) Representative photomicrographs illustrating the expression of KDR within human cardiac allografts. Top panels: immunohistochemical staining of KDR (rose brown color) in 3 human cardiac allografts with few (left top panel), moderate (middle top panel), and diffuse (right top panel) infiltrates. Middle and bottom panels: Immunofluorescence staining of CD3 and KDR in a representative cardiac allograft at ×400 magnification (middle) and 800× magnification (bottom). Merged images illustrate coexpression of CD3 and KDR (yellow color, arrows). (B) Confocal microscopy of a representative cardiac allograft with evidence of rejection illustrating coexpression of CD3 with KDR. (C) Scatter graphs showing the percentage of CD3⁺ stained T cells that coexpress KDR in cardiac and renal biopsies (black dots represent individual biopsies). The line shows the mean percent expression in all biopsies examined.