CHARACTERIZATION OF BLOOD-GROUP-ACTIVE ERYTHROCYTE-MEMBRANE GLYCOPROTEINS WITH HUMAN ANTISERA

Antisera to high- and low-incidence blood-group antigens were used in immunoblotting and immune precipitation studies to identify novel erythrocyte membrane components and to assign antigens to known proteins. Several antibodies identified well-characterized membrane proteins which are widely expressed on other cells and tissues. The Cromer system antigens were found to reside on the complement regulatory protein decay accelerating factor (DAF). Antigens of the Indian collection were located to the cell adhesion molecule, CD44. The Cartwright system antigens were assigned to acetylcholinesterase, the function of which, on erythrocytes, remains unclear. Two novel blood-group-active glycoproteins were identified. One carries the Scianna system antigens whilst the second carries the high-incidence antigens, Gy(a), Hy and Jo(a). The low-incidence antigens, Dh(a) and Rd, were assigned to Glycophorin C and to the Scianna-active glycoprotein, respectively. The existence of Cromer-null, DAF-deficient erythrocytes greatly facilitated the study of the function of DAF on erythrocytes. Location of the YT locus and hence of the AChE gene to chromosome 7q22 may be of significance in leukaemias and myelodysplasias since this region is a mutational 'hot spot' in these disorders. The novel proteins identified, for which no monoclonal antibodies are available, may also prove to be of functional significance on erythrocytes or on other cells and tissues. Several of the rare phenotype cells, such as the In(a - b -) cells, Gy(a -) cells and the Sc-null cells, may prove to be of great value in defining the function of these molecules on erythrocytes, in the way that Inab cells have been for studying the function of DAF.