Human Umbilical Vein Endothelial Cells Differ from Other Endothelial Cells in Failing to Express ABO Blood Group Antigens

Most in vitro investigations of endothelial cell function have been based on the behaviour of human umbilical vein endothelial cells (HUVEC) in primary tissue culture. However, it is becoming apparent that there is a marked degree of heterogeneity among endothelial cells derived from different vascular beds. We have studied primary HUVEC from 45 umbilical cords. Contrary to previously published reports, we were unable to detect ABO antigens on the surface of cultured HUVEC from group A or B cords. This was not due to an absence of precursor H substance which was uniformly expressed on HUVEC in primary tissue culture. Further investigation revealed an absence of A enzyme activity in A type HUVEC and a level of mRNA only just detectable by RT-PCR. The absence of functional A enzyme activity was confirmed by demonstrating the absence of A substance on von Willebrand factor secreted by A type cells. HUVEC appear to be the only vascular endothelial cells that do not express ABO blood group antigens. We speculate that this may help protect the cord from maternal antibodies during gestation. The lack of ABO blood group antigens on HUVEC may significantly affect their surface function, and therefore care should be taken when extrapolating conclusions from results obtained with these cells (the most widely used human endothelial cell model in vitro) to the properties of adult endothelial cells.