Endothelial cell hybrids and the suspension of factor VIII related antigen expression

Hybrid somatic cell clones have been generated by fusing human vascular endothelial cells in primary culture to cells of four rodent lines. Factor VIII related antigen (VIIIR:Ag) was clearly demonstrable in the cultured endothelial cells, even when they had been co-cultured with rodent cells. But in none of 14 hybrid clones was VIIIR:Ag detectable. Isozyme analyses for human chromosome markers show that all the assayed human chromosomes were represented among the hybrids, and that various subsets of human chromosomes have been deleted from individual hybrid clones. It may be concluded, therefore, either that VIIIR:Ag production depends on a particular combination of human chromosomes not represented in any of the hybrids, or that the rodent cells contribute some agent which intracellularly blocks VIIIR:Ag expression.