Phenotyping of peripheral blood hemopoietic progenitor cells--in vitro cultures using CD34-/CD33-immunomagnetic purging.

In contrast to many detailed studies on the antigenic profile of hemopoietic progenitor cells from human bone marrow, sparse information, so far, has been gathered with regard to the antigen expression of hemopoietic progenitors present in peripheral blood. Previous studies by multiparameter flow-cytometry have revealed substantial differences of the coexpression of the CD33-, CD19-, and CD74- antigens, respectively, on CD34-positive cells from blood versus those from bone marrow, respectively. Immunomagnetic purging with monoclonal antibodies detecting the CD34-, and the CD33- antigen, respectively, has been used to further characterize the expression of these antigens on day 8 and d-14 granulocyte/macrophage and erythroid colonies as grown from circulating progenitor cells. Purging with CD34 monoclonal antibody abrogated all colony formation, whereas purging with CD33 antibody led to differential inhibition of the various progenitors. Purging bone marrow cells with CD34 antibody, an inhibition of only about 25% was observed with regard to erythroid colonies, whereas an inhibition of about 85% was observed for CFU-GM. These findings reinforce the view that circulating progenitor cells represent relatively immature stages of differentiation, when compared to bone marrow progenitors. Particularly, d-8 erythroid colonies from blood do not represent the equivalent of the genuine CFU-E as described from bone marrow, but they seem to be early stages of BFU-E development.