Selective enrichment in human megakaryocyte progenitors by the B203.13 surfacedifferentiation antigen

The B203.13 monoclonal antibody specifically recognizes a subset (8-18.5%) of human CD34+ haemopoietic progenitors, which are significantly (P<0.05) enriched in megakaryocyte progenitors (CFU-meg). Moreover B203.13 expression was progressively lost as maturation proceeded along the megakaryocytic lineage. In fact: (i) CFU-meg derived from CD34+/B203.13+ showed a greater number of cells/colony with respect to CD34+/B203.13-; (ii) after 10 d of liquid cultures with 100 ng/ml of thrombopoietin, only a minority of CD34-derived cells positive for CD41 coexpressed B203.13; (iii) in situ immunocytochemical staining revealed that B203.13 was expressed exclusively on immature megakaryoblasts; (iv) circulating platelets did not express B203.13.