Methodologic and genetic influence on immunohistochemical demonstration and semiquantitation of blood group antigen A in human ureter urothelium.

In order to improve the accuracy and prognostic value of ABH blood group antigen loss in urothelial tumors, the effect of Lewis blood type and methodologic factors on detectability and distribution of blood group antigen A in human formalin-fixed, paraplast-embedded urothelium and endothelium was investigated by means of the Tween 20-modified indirect immunoperoxidase staining technique. Urothelium of Lea-b+ and Lea-b- individuals expressed significant higher amounts of blood group antigen A compared to urothelium of Lea+b- individuals. The expression on endothelial cells was related to vessel type and size, but not related to Lewis types. Compared to human anti-A, monoclonal anti-A demonstrated blood group antigen A with higher sensitivity and, due to reduced background staining, higher specificity. Consequently monoclonal anti-A detected blood group antigen A in the urothelium of Lea+b- individuals where human anti-A failed to stain, and different staining patterns became apparent. Both a two- to fourfold variation in the proportion between tissue section area and volume, and the volume of anti-A applied induced minor changes in sensitivity and specificity. The monoclonal anti-A method and knowledge about erythrocyte Lewis types might prove valuable in evaluating changes in blood group antigen-A expression in urothelial tumors.