Secretion/intracellular retention of type 2A VWD variants. (A) Homozygous expression of variant VWF in HEK293T cells. (B) Heterozygous expression (1:1 ratio) of variant VWF and WT-VWF. The concentration of VWF in the conditioned medium (black bars) and cell lysate (gray bars) was assessed by VWF ELISA for each VWF variant and compared with WT-VWF. VWF:Ag levels are expressed as a percentage of WT. Each column represents the mean ± SD of at least 3 separate experiments. Secretion of several VWF variants is reduced markedly.