Kinetic study of HLA-DR antigen expression during growth factor–induced CD34⁺ proliferation and differentiation. Isolated CD34⁺ cells were cultured in IMDM containing 10% FCS and 7 cytokines (IL-1, IL-3, IL-6, SCF, EPO, G-CSF, and GM-CSF ). And the indicated time (days 0, 4, or 7), cells were harvested, stained by FITC-conjugated MoAb to HLA-DR, and examined for HLA-DR antigen expression by flow cytometric analysis.