Reproducibility of Complement 4d deposition by immunofluorescence and immunohistochemistry in lung allograft biopsies

Agreement of IF-based C4d staining in lung allografts appears superior to that of IHC. However, overall agreement for IF and IHC among pathologists is sub-optimal and correlation between IF and IHC is low, although this may be influenced in part by the low variability of the results given the mostly negative biopsies. C4d 3+ may be specific for AMR, although rare. A multidisciplinary approach seems to be the best way to diagnose AMR in lung allograft biopsies.