IL-23 is a novel cytokine composed of an IL-12 p40 and a p19 subunit. We analyzed human peripheral blood mononuclear cells (PBMC) and hematopoietic cell lines for constitutive expression of IL-23 and IL-12 subunits and expression following exposure to various stimuli, and investigated the mechanisms of their induction by LPS and SAC. IL-23 p19 and IL-12 p35 mRNAs were expressed in fresh PBMC, and expression of all IL-23 and IL-12 subunits was up-regulated by LPS and SAC. LPS-induced increase of IL-23 and IL-12 subunits expression was CD14-dependent, while CD14 was not involved in SAC-induced p19 transcription. Both LPS-and SAC-induced subunits expression required p38 MAPK pathway. PHA effected an increase of p19 mRNA in both CD4C and CD8C T cells, whereas p35 was minimally regulated by PHA. IFN-g primed monocytes for LPS stimulation of p19, p35 and p40 expression. p19 mRNA was detectable in most hematopoietic cell lines tested but p35 distribution was more restricted. A phorbol diester enhanced p19, p35 and p40 expression in EBV-positive cell lines. Our results suggest that both the subunits of IL-23 are tightly regulated; the expression pattern and regulation mode of IL-23 p19 is similar to as well as distinct from that of IL-12 p35.

The transmigration of hematopoietic progenitor cells is a crucial step in the homing of transplanted stem cells into bone marrow (BM) microenvironment; however, the molecular basis for this is not fully understood. Matrix metalloproteinases (MMPs), which are implicated in the migration of leukocytes, are important in degrading components of extracellular matrix molecules. In this study, using zymographic analysis and enzyme-linked immunosorbent assay (ELISA), we investigated the production of MMP-9 in CD34+ cells from cord blood (CB) and BM, compared their spontaneous migration across a reconstituted basement membrane-coated filter in transwell, and studied the role of MMP-9 in the transmigration. Zymography and ELISA showed that MMP-9 is produced by freshly isolated CD34+ stem/progenitor cells obtained from CB. CB CD34+ cells showed significantly higher migrational capacity than BM CD34+ cells (p=0.008). Furthermore, the migrational ability of CB CD34+ cells over the extracellular matrix (ECM) was significantly inhibited by the inhibitor of MMP, o-phenanthroline and anti-MMP-9 monoclonal antibody (73.3€11.8% and 37.5€10.4% inhibition, respectively). Our results strengthen the potential role of MMP-9 in the higher migrational capacity of CB CD34+ cells, which may be beneficial to homing of these cells to the BM environment.

Earlier studies indicate that J6-1 human leukemic cells proliferate and propagate via the membrane-bound macrophage colony-stimulating factor (M-CSF)-mediated auto-juxtacrine mechanism. Matrix metalloproteinases (MMPs) can modulate the activity of cell membrane molecules and influence many cellular behaviors. Therefore, we hypothesized that MMP may also be involved in the membrane-bound M-CSF-mediated juxtacrine mechanism. First, we investigated whether blocking of membrane-bound M-CSF by neutralizing antibody to M-CSF or M-CSF receptor and adding of exogenous M-CSF are able to influence MMP-9 release. Next, we determined whether MMP-9 participated in J6-1 cells proliferation and influence the shedding of membrane-bound M-CSF and its receptor. Current studies show that blockade of the interaction between membrane-bound M-CSF and M-CSF receptor by antibody to M-CSF or M-CSF receptor promotes MMP-9 release. Moreover, we demonstrated that because of M-CSF mediated juxtacrine, lack of MMP-9 promotes J6-1 cell proliferation, in which a decrease in the shedding of cell-surface M-CSFR is involved. Hence, we suggest that membrane-bound M-CSF inhibit MMP-9 release and down-regulated MMP-9 contribute to juxtacrine stimulating in leukemic cell growth.

Background and Objectives. The prevalence and pathogenic role of human herpesvirus 6 (HHV-6) in various benign and malignant hematologic diseases remain largely unknown. The aim of this study was to search for a possible involvement of HHV-6 in the pathogenesis of hematologic diseases. Design and Methods. The presence of HHV-6 DNA sequences was examined by polymerase chain reaction (PCR) in bone marrow mononuclear cells from 241 patients with benign and malignant hematologic diseases in China. Platelet-associated immunoglobulin (PAIg) of 66 idiopathic thrombocytopenic purpura (ITP) patients was measured by competitive enzyme-linked immunosorbent assay. The presence of HHV-6 DNA in sera from 31 ITP patients was examined by PCR. Paired serum samples from 19 ITP patients were analyzed for anti-HHV-6 IgG titers using an indirect immunofluorescence assay. Results. HHV-6 DNA was detected in 41% and 37.5% of ITP and acute leukemia patients respectively, but in only 6.7% of patients with iron deficiency anemia. HHV-6 positivity for ITP patients with excessive PAIgG was significantly higher than in patients with a normal level of PAIgG. HHV-6 DNA was not detected in any of the serum samples from ITP patients. None of the 19 cases of ITP showed a significant increase in anti-HHV-6 antibody titers during the convalescent phase compared with the onset phase. Interpretation and Conclusions. Our results indicate that HHV-6 infection might be associated with excessive PAIgG in some cases of ITP, and that the virus persists in a latent state. The pathogenic role of HHV-6 in ITP needs to be confirmed by further investigations.