Water‐Soluble I Blood Group Substance in the Secretions of i Adults

Abstract

Water‐soluble I blood group substance has been found in the saliva and milk of an i adult woman. The serum of the propositus contained iso anti‐I that could be partially inhibited by her own milk. Neither secretion had excessive inhibitory activity against anti‐i. The results suggest that the gene Z, believed to be necessary for red blood cell I antigen development, is not required for synthesis of secretory I substance. The i adult phenotype is thus closely comparable with the A m and B m phenotypes in which expression of A and B is modified in the red blood cells but not in the secretions.