Release of adherent human BM CD34⁺ HPCs.

The release of human BM CD34⁺ HPCs adhered to human BM stromal cell monolayers (A) or immobilized rhuVCAM-1 (B) is shown. CD34⁺ HPC were adhered for 30 minutes at 37°C and then incubated for 1 hour in the presence of either conditioned medium or purified proteases. The percentage of cells remaining adherent was quantified. (C) Neutrophil-conditioned medium was preincubated without (●) or with 1 mg/mL α₂-macrobulin (○) before addition to CD34⁺ HPC adhered to BM stromal cell monolayers. Results are expressed as the mean of triplicates ± SD. The experiment was repeated 3 times. CM indicates conditioned medium.