Variable localization of blood group antigen in group A kidneys

The distribution of the blood group A antigen has been examined in 7 Group A kidneys using an indirect immunoperoxidase technique. Monoclonal antibody consistently demonstrated A antigen on the endothelium of all kidneys, particularly peritubular capillary endothelial cells and also the epithelial cells of distal tubules of all but 1 case. Nine hyperimmune anti-A alloantisera gave a variable pattern of staining on different endothelial cells, but no kidney was negative. Epithelial cell staining showed considerable variation both within an individual cell and between adjacent cells. Twenty-six out of 40 alloantisera from normal Group O blood donors failed to bind to endothelial cells of one kidney which was known to show strong expression of A antigen. Absorption was completely achieved using Group A red blood cells but not with a synthetic blood group substance. The variation in reaction intensity using different antisera emphasises that there is variation in antigen expression between cells and indicates the complexity of antibodies directed against the blood group A antigen.