GRANULOMONOCYTE-ASSOCIATED LYSOSOMAL PROTEIN EXPRESSION DURING IN-VITRO EXPANSION AND DIFFERENTIATION OF CD34(+) HEMATOPOIETIC PROGENITOR CELLS

Using an in vitro expansion and differentiation system for human CD34( +) cord blood (CB) progenitor cells, we analyzed the induction and exp ression kinetics of the granulomoncyte associated lysosomal proteins m yeloperoxidase (MPO), lysozyme (LZ), lactoferrin (LF), and macrosialin (CD68). Freshly isolated CD34(+) CB cells were negative for FZ and LF , and only small proportions expressed MPO (4% +/- 2%) or CD68 (3% +/- 1%). Culturing of CD34(+) cells for 14 days with interleukin (IL)-1, IL-3, IL-6, stem cell factor, granulocyte-macrophage colony-stimulatin g factor (GM-CSF), and G-CSF resulted in on average a 1,750-fold ampli fication of cell number, of which 83% +/- 746 were MPO(+). Without add ition of GM-CSF and G-CSF, lower increases in total cell numbers (mean , 211-fold) and lower proportions of MPO(+) cells (54% +/- 11%) were o bserved. The proportion of MPO(+) cells slightly exceeded but clearly correlated with the proportion of cells positive for the granulomonocy te associated surface molecules CD11b (Mac-1), CD15 (LeX). CD64 (Fc ga mma R1) CD66, or CD89 (Fc alpha R). At day 14 MPO(+) and LZ(+) cells w ere virtually identical. However, at earlier time points during cultur e (days 4 and 7), single MPO(+) or LZ(+) cell populations were also ob served, which only later acquired LZ and MPO, respectively. Maturation of cells into the neutrophilic pathway was indicated by the acquisiti on of MPO, followed by LZ. In contrast, maturation of cells into the m onocytic pathway was indicated by the acquisition of LZ followed by MP O and CD14. CD68 was found to be expressed at day 4 by the majority of cells and was not restricted to the granulomonocytic cells, as cells with megakariocytic (CD41(+)) or erythroid (CD7l(hi)) features were CD 68(+). LF expression was observed only in GM- plus G-CSF-supplemented cultures, in which only 26% +/- 5% of cells expressed LF by day 14. (C ) 1995 by The American Society of Hematology.