Immunocytochemical staining for MMP-9. BMCMCs incubated with rIL-3 (a) or with 100 ng/mL rSCF (b) for 72 hours were fixed in 4% paraformaldehyde and treated with anti–MMP-9 antibody. BMCMCs incubated with rSCF show a weak reaction or no reaction for MMP-9.