Fluorescent microscopic images (×400 magnification) of double immunofluorescence staining on frozen tissue from an allograft on POD 20. a A section taining with anti-rat ED1 mAb (for macrophages; arrows, red). b The same section as Panel A staining with anti-rat RT1.Aa,b,l mAb (for rat PVG.R8; arrows, green). The images shown in Panels a and b were taken over the same field of view, while Panel c is an overlay image of a and b. These data indicate that recipient immune cells, mainly macrophages, are present at early stages of chronic cardiac rejection. (From Ye et al. [26•]; with permission)