Glycoprotein IIb-IIIa is expressed on avian multilineage hematopoietic progenitor cells

The fibrinogen receptor GPIIb-IIIa integrin is known to be expressed on cel ls of the megakaryocytic lineage, but its presence on hematopoietic progeni tors has been a controversial issue, To resolve this ambiguity unequivocall y, we performed clonogenic assays and intrathymic cell-transfer experiments in congenic animals. As the ontogeny of the avian hematopoietic system is well documented, we used this experimental model to trace GPIIb-IIIa expres sion during embryogenesis, Consequently, we now report that the GPIIb-IIIa integrin is expressed as early as embryonic day 3.5 (E3.5) to 4 in intraaor tic hematopoietic clusters, the first site of intraembryonic hematopoietic progenitor emergence, and later in E6 paraaortic foci. Myeloid and erythroi d progenitors were also detected within the GPIIb-IIIa(+) CD45(+) populatio n isolated from the E3.5 to 4 aortic area, while in embryonic and adult bon e marrow, myeloid, erythroid, and T-cell progenitors were present in the GP IIb-IIIa(+) c-kit(+) population. Furthermore, we also provide the first evi dence, that GPIIb-IIIa(+) bone marrow cells can differentiate into T cells. Hence, GPIIb-IIIa can be used as a marker for multilineage hematopoietic p ro genito rs, permitting identification of early intraembryonic sites of he matopoiesis, as well as the isolation of embryonic and adult hematopoietic progenitors. (C) 1999 by The American Society of Hematology.