Blood group O expression in normal tissues and tumors.

The H antigen (O blood group), the precursor to A and B blood groups, is expressed on human erythrocytes and other cells (e.g., endothelial cells). Remarkably, the specific expression of the H antigens is uncertain due to the lack of specific reagents for its detection. Here, we describe two monoclonal antibodies (mAbs), Tn4-31L and OmcFL3-02, generated by immunizing sea lampreys with human cells. Both mAbs are highly specific in comparison with the lectin Ulex europaeus agglutinin-I (UEA-I). We identified expression of H antigens in mammalian glycoproteins, human cells, and normal and malignant human tissues, discovering that different types of human carcinomas exhibit unexpected H antigen expression. Interestingly, H antigen detection in many cases was distinctly elevated by enzymatic desialylation, as well as being elevated in cells engineered to lack sialic acid. These highly specific mAbs will be valuable reagents in blood testing and for exploring the expression and function of H antigens.