Use of the OP9 stromal cell line enhances the number and duration of neutrophils produced. The effects of OP9 cells on the number and duration of neutrophils produced in a single well (9.5 cm2 growth area) of a 6-well plate over 26 days from a representative experiment is shown. At the indicated times in the neutrophil differentiation mix, 1 mL of cells in suspension following gentle flushing was retrieved and counted using a hemacytometer as described in “Materials and methods.” Multiple wells were assayed in sequence to enable evaluation of each well every 8 days, which eliminated any effect of cell removal on the cell number. In the OP9 group, cells were differentiated in the presence of the OP9 cells starting at the gp-130 differentiation medium (□, –OP9; ⋄, + OP9 cells). Error bars represent standard deviations.
