Description: The monoclonal antibody 17-206 recognizes the human blood group antigen H (O) type 1, a subtype primarily found in epithelial and secretory cells. The precursor H antigen is modified by addition of saccharides to carbohydrate chains of proteins and lipids on erythrocytes and epithelial cells. The type, attachment, location, and sequence of saccharides determines the blood group antigen subtype and is mediated by multiple glycosyl transferases. Depending on ABO blood type, the H antigen is converted into either the A antigen, B antigen, both the A and B antigen, or left unconverted (O antigen). Evidence that the blood group antigen H is not expressed in tumor cells and that the level correlates with disease progression suggests that the blood group antigen H may be involved in cell proliferation, cell adhesion, and angiogenesis, although its exact function remains to be determined. The 17-206 antibody does not recognize blood group antigen H (O) type 2.