Diagnosis of renal allograft rejection by macrophage immunostaining with a CD14 monoclonal antibody, WT14.

Since acute interstitial rejection (AIR) of renal allografts is accompanied by an increase of macrophages in the graft the diagnostic value of immunohistological staining of biopsy specimens with WT14, a new monoclonal antibody of the CD14 cluster directed against monocytes/macrophages, with increased affinity for activated cells, has been tested retrospectively. With an indirect immunoperoxidase technique on frozen sections a diffuse interstitial increase of WT14-positive cells was seen, with a characteristic peritubular pattern, in all 44 patients with clinically and histologically proven AIR. This pattern was not seen in normal kidneys (n = 10), or in biopsy specimens from patients with proven cyclosporin nephrotoxicity (n = 9), chronic vascular rejection (n = 13), or various other renal diseases (n = 60). Comparative staining with other monoclonal antibodies against monocytes/macrophages showed a variable, mostly weak or less specific staining pattern than did WT14. The increased staining with WT14 proved to be a better indicator of AIR than increased HLA-DR staining on tubular epithelial cells.