Previously, we demonstrated that IL-8 induces rapid mobilization of hematopoietic progenitor cells (HPC) from the bone marrow of rhesus monkeys. Because activation of neutrophils by IL-8 induces the release of gelatinase B (MMP-9), which is involved in the degradation of extracellular matrix molecules, we hypothesized that MMP-9 release might induce stem cell mobilization by cleaving matrix molecules to which stem cells are attached. Rhesus monkeys were treated with a single i.v. injection of 0.1 mg͞kg human IL-8, which resulted in a 10-to 100-fold increase in HPC within 30 min after injection. Zymographic analysis revealed a dramatic instantaneous increase in the plasma levels of MMP-9, followed by the increase in circulating HPC. Enzyme levels decreased at 2 h after injection of IL-8, simultaneously with the decrease in the numbers of circulating HPC. To test the hypothesis that MMP-9 induction was involved in HPC mobilization, rhesus monkeys were treated with a highly specific inhibitory monoclonal anti-gelatinase B antibody. Anti-gelatinase B at a dose of 1-2 mg͞kg completely prevented the IL-8-induced mobilization of HPC, whereas a dose of 0.1 mg͞kg had only a limited effect. Preinjection of inhibitory antibodies did not preclude the IL-8-induced production and secretion of MMP-9. Pretreatment with an irrelevant control antibody did not affect IL-8-induced mobilization, showing that the inhibition by the anti-gelatinase B antibody was specific. In summary, IL-8 induces the rapid systemic release of MMP-9 with concurrent mobilization of HPC that is prevented by pretreatment with an inhibitory anti-gelatinase B antibody, indicating that MMP-9 is involved as a mediator of the IL-8-induced mobilization of HPC.

The graft-versus-myeloma (GVM) effect of donor lymphocyte infusions (DLIs) is well established. We now report the outcome of DLI in 54 patients with relapsed myeloma following allogeneic transplantation. Twenty-eight patients (52%) responded, 19 patients (35%) with a partial response and 9 patients (17%) with a complete response. Progression-free and overall survival were 19 and 23 months, respectively. We found that acute and chronic graft-versus-host disease (GVHD) observed in 57% and 47% of patients, respectively, following DLI were the strongest predictors for response. This suggests that targets for GVHD and GVM are identical. In a subgroup analysis, deletion of chromosome 13, as determined by double-color fluorescence in situ hybridization (FISH), had no impact on outcome, indicating that these patients are candidates for early allogeneic transplantation followed by DLI, in case of insufficient response. (Blood. 2004;103:4362-4364)