This antibody reacts with H type 2 blood group epitope Fuca1-2 Galb1-4 GlcNAc. It does not cross-react with human blood group H type 1, 3 or 4, nor with the closely related type 2 antigen Ley and Lex. Blood-group antigens are generally defined as molecules formed by sequential addition of saccharides to the carbohydrate side chains of lipids and proteins detected on erythrocytes and certain epithelial cells. The A, B and H antigens are reported to undergo modulation during malignant cellular trans- formation. Blood group related antigens are usually mucin-type and are detected on erythrocytes, certain epithelial cells and in secretions of certain individuals. Sixteen genetically and biosynthetically distinct but inter-related specificities belong to this group of antigens, including A (1 and 2), B, H (1 and 2), M, N, Lewis A, Lewis B, Lewis X, Lewis Y and precursor type 1 chain antigens. The expressions of the H1 and H2 in different cell types are con- trolled by different genes.