The extent of peritubular CD14 staining in renal allografts as an independent immunohistological marker for acute rejection

Previously, we demonstrated that in acute interstitial rejection, immunohistological staining of renal allograft biopsies with the CD14 mAb WT14, reacting with human monocytes/macrophages, shows a characteristic peritubular increase of positive cells. To test the diagnostic value of this CD14 positivity, we compared, in 154 unselected renal allograft biopsies, the extent of peritubular WT14 staining with (a) the original histological diagnosis, made with knowledge of clinical data, (b) the retrospectively and blindly scored histological diagnosis according to the criteria of the Banff classification, and (c) the eventual clinical diagnosis, which included evaluation of the response to therapy. The extent of peritubular WT14 positivity, blindly scored on cryostat sections of the frozen part of the biopsies, correlated positively with the probability of acute rejection (AR). When using a cutoff of 70% WT14 positivity for the diagnosis of AR, as extracted from a receiver operating characteristic curve, the WT14 diagnosis had a positive predictive value of 91% and a negative predictive value of 56%, compared with the original histological diagnosis. Compared with the Banff diagnosis of AR (grade I-III), these values were 95% and 47%, and compared with the clinical diagnosis, 84% and 63%, respectively. The WT14 diagnosis essentially corrected the original histological diagnosis in 7 cases, and was consistent with the eventual diagnosis in 5 equivocal cases. We conclude that the extent of peritubular CD14 positivity can be used as a marker for AR and can serve as a valuable additional criterion for AR in the histological examination of renal allograft biopsies.