Fluorescent microscopic images (magnification ×400) of double immunofluorescent staining on frozen tissue from an allograft on POD 20. A, A section staining with anti-rat ED1 mAb (for macrophages, arrows, red). B, The same section as A, staining with anti-rat RT1.Aa,b,l mAb (for rat PVG.R8, arrows, green). The images shown in A and B were taken over the same field of view; C is an overlay image of A and B. These data indicate that recipient immune cells, mainly macrophages, are present at the early stages of chronic CR.