Expression of antigens of the platelet glycoprotein IIb/IIIa complex on human hematopoietic stem cells.

Several cell surface and cytoplasmic markers specific for the megakaryocyte-platelet lineage have been described. However, as yet, none of these has been shown to be expressed on cells earlier than the committed megakaryocyte progenitor, CFU-Meg. The present study was aimed at determining whether platelet lineage antigens could be detected on human pluripotential stem cells. Rabbit antiserum against human platelets (APS) was extensively absorbed with erythrocytes and either platelets, neutrophils, monocytes, or cells of the monocytic cell line U937. The anti-stem cell antibodies in each absorbed antiserum were determined using a complement-dependent cytotoxic assay for the pluripotential stem cell CFU-mix. Platelets alone removed anti-stem cell antibodies from APS. Absorption of APS with platelets from a patient with Glanzmann's thrombasthenia failed to remove the anti-stem cell activity, providing evidence for involvement of the platelet glycoprotein IIb/IIIa complex. Antiserum against purified glycoprotein IIb and against glycoprotein IIIa also recognized stem cells, resulting in reduced formation of mixed colonies. Absorption of these antisera with normal platelets removed the anti-stem cell activity, indicating that both IIb and IIIa are represented on stem cells. Hence, cell surface antigens specific for the stem cell-megakaryocyte-platelet pathway are expressed on the platelet glycoprotein IIb/IIIa complex.