Antigenic characteristics of circulating granulocyte-macrophage progenitors (CFU-GM) in idiopathic myelofibrosis and polycythaemia vera defined by monoclonal antibodies.

The antigenic characteristics of "early" (type 1) and "late" (type 2) granulocyte-macrophage progenitor cells (CFU-GM) from patients with polycythaemia vera (PV) and idiopathic myelofibrosis (MF) were studied using antimyeloid murine monoclonal antibodies (McAbs) and anti-HLA-DR McAb (L243) in a complement dependent cytotoxic assay followed by culture in methyl cellulose. The results were compared with the previously published data on the antigen phenotype of CFU-GM from normal bone marrow and peripheral blood. McAbs L243, MY9, S3-13 and S17-25 reacted with lower percentage of CFU-GM from patients with PV and MF than with their normal counterparts MCAbs R1.B19 and WGHS 29.1, which recognized the antigens on "late" CFU-GM (type 2), reacted with a high proportion of day 7 CFU-GM from MF peripheral blood and normal marrow but did not react with CFU-GM from PV and normal peripheral blood. The antigens recognized by two other McAbs (53/10 and PM81) were present on some of normal CFU-GM and were not found on CFU-GM from MF and PV peripheral blood. Our data suggest that CFU-GM in the circulation in MF differ from those in normal blood, perhaps because they are released from the spleen which in this disease has haemopoietic function.