No response to G-CSF in elastase-treated CD34⁺ cells.

CD34⁺cells (10⁵/mL) were cultured in the presence of 10 ng/mL cytokine with or without 1 μg/mL elastase. Proliferation was measured daily by tritiated thymidine uptake. (A) No proliferation in response to G-CSF in elastase-treated culture. ● indicates control; and ○, elastase. Data are representative of 3 independent experiments. (B) Proliferation in response to GM-CSF or SCF but not G-CSF in the presence of elastase (1 μg/mL). ○ indicates G-CSF; ■, GM-CSF; and ▵, SCF. Data are representative of 3 independent experiments. (C) Loss of synergy between GM-CSF and G-CSF in elastase-treated cultures. Data presented are the mean (± SEM) of triplicates. ● indicates control GM-CSF; ▪, control GM-CSF + G-CSF; ○, elastase GM-CSF; and ■, elastase GM-CSF + G-CSF. (D) Proliferation response to G-CSF incubated with increasing doses of elastase (mean ± SEM of triplicates). ● indicates control; *, no G-CSF/no elastase; ○, 1 μg/mL elastase; ■, 500 ng/mL elastase; ▵, 250 ng/mL elastase; and +, 62.5 ng/mL elastase).