P1PK, GLOB, and FORS Blood Group Systems and GLOB Collection: Biochemical and Clinical Aspects. Do We Understand It All Yet?

Antigens belonging to the P1PK, GLOB, and FORS blood group systems and the GLOB blood group collection represent a closely related set of 13 glycosphingolipids (GSLs). They are synthesized by the coordinated action of glycosyltransferases, encoded by at least 7 different loci. Three of these enzymes show either different activity or a different mRNA expression profile due to genetic polymorphisms, resulting in blood group diversity. In recent years, significant progress has been made in understanding the molecular background and biological functions of these GSLs. Their medical significance is often related to the existence of natural antibodies, as they may cause complications after transfusions and during pregnancies. In addition, GSLs belonging to these blood group systems are receptors for several pathogens. This review summarizes the present knowledge about the complicated network of enzymatic interactions leading to synthesis of these GSLs, as well as their clinical implications.