Different expression of CD41 on human lymphoid and myeloid progenitors from adults and neonates

The glycoprotein (Gp) IIb/IIIa integrin, also called CD41, is the platelet receptor for fibrinogen and several other extracellular matrix molecules. R ecent evidence suggests that its expression is much wider in the hematopoie tic system than was previously thought. To investigate the precise expressi on of the CD41 antigen during megakaryocyte (MK) differentiation, CD34(+) c ells from cord blood and mobilized blood cells from adults were grown for 6 days in the presence of stem cell factor and thrombopoietin. Two different pathways of differentiation were observed: one in the adult and one in the neonate cells. In the neonate samples, early MK differentiation proceeded from CD34(+)CD41(-) through a CD34(-)CD41(+)CD42(-) stage of differentiatio n to more mature cells. In contrast, in the adult samples, CD41 and CD42 we re co-expressed on a CD34(+) cell. The rare CD34(+)CD41(+)CD42(-) cell subs et in neonates was not committed to MK differentiation but contained cells with all myeloid and lymphoid potentialities along with long-term culture i nitiating cells (LTC-ICs) and nonobese diabetic/severe combined immune-defi cient repopulating cells. In the adult samples, the CD34(+)CD41(+)CD42(-) s ubset was enriched in MK progenitors, but also contained erythroid progenit ors, rare myeloid progenitors, and some LTC-ICs. All together, these result s demonstrate that the CD41 antigen is expressed at a low level on primitiv e hematopoietic cells with a myeloid and lymphoid potential and that its ex pression is ontogenically regulated, leading to marked differences in the s urface antigenic properties of differentiating megakaryocytic cells from ne onates and adults. (Blood, 2001;97: 2023-2030) (C) 2001 by The American Soc iety of Hematology.