Maternal administration of granulocyte colony-stimulating factor improves neonatal rat survival after a lethal group B streptococcal infection

Maternally administered recombinant human granulocyte colony- stimulating factor (rhG-CSF) has been shown to cross the placenta and induce a peripheral neutrophilia and increases in the marrow and spleen neutrophil storage pools in fetal and newborn rats. In the present study, we have used this model system to investigate the efficacy of prenatally administered rhG-CSF on neonatal defense to a lethal challenge with Group B-beta hemolytic Streptococcus (GBS). Pregnant rats were injected with rhG-CSF twice daily beginning 6 days before parturition. At birth, all pups were infected with a dose of GBS that is lethal for 90% of infected pups (LD90). Survival was monitored daily for 5 days. Survival of infected pups from saline-treated mothers beyond 60 hours after infection was 10%. No difference in survival was observed among pups from mothers treated 2 and 4 days before parturition. In contrast, we determined that survival was 82.5% among infected pups from mothers treated for 6 days before parturition with rhG-CSF. Our results demonstrate that maternal administration of rhG- CSF augments neonatal defenses against a lethal bacterial challenge.     

Importance of catalase in the disposal of hydrogen peroxide within human erythrocytes

The catalase within normal, intact human erythrocytes was completely inactivated with amino triazole. The rate of 14CO2 evolution, when the cells were subsequently incubated with 14C-labeled glucose, provided a measure of the rate at which NADPH was being oxidized by the glutathione peroxidase/reductase system for the disposal of H2O2. This rate was determined in control cells and in catalase-inactivated cells while the cells were exposed to H2O2, which was generated at various constant and predetermined rates by glucose oxidase. The results indicated that catalase handles approximately half of the generated H2O2. The glutathione peroxidase/reductase mechanism accounted for the other half. These results are in agreement with our earlier findings on erythrocytes of a subject with a genetic deficiency of catalase. However, an unexpected result with the present approach was the finding that the increased dependence on the glutathione peroxidase/reductase mechanism did not occur until greater than 98% of the catalase had been inactivated. The latter observation indicates that catalase and the glutathione peroxidase/reductase system function intracellularly in a manner very different from that previously ascribed to them. An explanation of the findings requires that the two methods of H2O2 disposal function in a coordinated way, such as a sequential action in which the glutathione peroxidase/reductase system is the rate-limiting step.     

Kinetics of anti-CMV antibodies after administration of intravenous immunoglobulins to bone marrow transplant recipients

Polyspecific iv immunoglobulins (IVIG) are routinely used to prevent cytomegalovirus (CMV) infections in bone marrow transplant recipients; however, the plasma disappearance pattern of CMV-specific antibodies after administration of this product remains unclear because conflicting kinetic data have been reported previously. We studied the half-life of CMV-specific antibodies in 9 patients undergoing bone marrow transplantation after administration of 500 mg/kg of a conventional polyspecific IVIG preparation (Sandoglobulin, Sandoz Pharmaceuticals). Eight serial blood samples were drawn for kinetic evaluation after the dose. The titer of CMV-specific antibodies in the sample was determined by the FIAX method, and the decay curves of CMV-specific antibodies were analyzed kinetically using model-independent method. The 9 kinetic curves showed that a titer above 20 Fiax units was maintained for only 7 days after dosing. The mean half-life of CMV-specific antibodies was 5.6 days (range 3.5 to 12.5 days), indicating that their elimination rate was much faster than that found in several other studies. Our results suggest that the optimal dosing interval for these products is around 1 week in bone marrow transplant recipients.     

Granulocyte-macrophage colony-stimulating factor augmentation of T-cell receptor-dependent and T-cell receptor-independent thymocyte proliferation

The effects of granulocyte-macrophage colony-stimulating factor (GM- CSF) are not confined to cells of the myeloid lineage. GM-CSF has been shown to have effects on mature T cells and both mature and immature T- cell lines. We therefore examined the GM-CSF responsiveness of murine thymocytes to investigate whether GM-CSF also affected normal immature T lymphocytes. The studies presented here indicate that GM-CSF augments accessory cell (AC)-dependent T-cell receptor (TCR)-mediated proliferation of unseparated thymocyte populations. To identify the GM- CSF responsive cell type, thymic AC and T cells were examined for GM- CSF responsiveness. We found that GM-CSF augmentation of TCR-induced thymocyte proliferation appears to be mediated via augmentation of AC function, and not via direct effects on mature single-positive (SP) thymocytes. Enriched double-negative (DN) thymocytes were also tested for GM-CSF responsiveness. GM-CSF induced the proliferation of adult and fetal DN thymocytes in an AC-independent and TCR-independent single- cell assay. Thus, in contrast to the SP thymocytes, a DN thymocyte population was directly responsive to GM-CSF. GM-CSF therefore may play a direct role in the expansion of DN thymocytes and an indirect role in the expansion of SP thymocytes.     

Liposomal delivery of methylphosphonate antisense oligodeoxynucleotides in chronic myelogenous leukemia [see comments]

Chronic myelogenous leukemia (CML) is a hematologic malignancy characterized by the presence of the Philadelphia (Ph) chromosome. Bcr- abl, the fusion gene associated with the Ph chromosome, expresses a p210bcr-abl protein that promotes a selective expansion of mature myeloid progenitor cells. Methylphosphonate (MP) oligodeoxynucleotides complementary to specific regions of the bcr-abl mRNA were incorporated in liposomes. We studied the effects of liposomal MP (L-MP) on the growth inhibition of CML-like cell lines. L-MP targeted to the breakpoint junctions of the bcr-abl mRNA inhibited the growth of CML cells. Fifty percent inhibition was achieved at approximately 1 mumol/L of L-MP oligonucleotide concentrations. The inhibitory effect was selective because growth inhibition was observed only with CML but not with control cell lines. Moreover, CML cell growth inhibition was dependent on the sequence of the MP oligodeoxynucleotides incorporated in the liposomes. The growth inhibition of CML cells by L-MP resulted from selective inhibition of the expression of the p210bcr-abl protein.     

In vivo stimulation of megakaryocytopoiesis by recombinant murine granulocyte-macrophage colony-stimulating factor

Murine recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) was injected in mice, and the effects on bone marrow, splenic megakaryocytes, megakaryocyte precursors (megakaryocyte colony-forming units [CFU-Meg]) were evaluated. In mice injected three times a day for 6 days with 12,000 to 120,000 U rGM-CSF, no significant modification of both platelet levels and mean platelet volume was observed, while there was a twofold increase in blood neutrophils. However, the rate of platelet production, as assessed by the measurement of 75selenomethionine incorporation into blood platelets, was On the contrary, administration of up to 384,000 U rGM-CSF two times a day for 2 days, as for a typical "thrombopoietin assay," failed to modify platelet production. A significant dose-related increase in the number of splenic megakaryocytes occurred in mice receiving 60,000 to 120,000 U rGM-CSF, while a slight increase in the number of bone marrow megakaryocytes was observed in mice injected with 120,000 U rGM-CSF. The proportion of bone marrow megakaryocytes with a size less than 18 microns and greater than 35 microns resulted significantly higher in mice receiving rGM-CSF in comparison with controls; an increase in the percentage of splenic megakaryocytes greater than 35 microns was also observed. A statistically significant increase in the total spleen content of CFU-Meg was observed after administration of 90,000 and 120,000 U rGM-CSF three times a day for 6 days, while no effect on bone marrow CFU-Meg was recorded, irrespective of the dose delivered. Finally, 24 hours after a single intravenous injection of rGM-CSF, there was a significant increase in the proportion of CFU-Meg in S-phase, with the splenic progenitors being more sensitive than bone marrow-derived CFU-Meg. These data indicate that rGM-CSF has in vivo megakaryocyte stimulatory activity, and are consistent with previous in vitro observations. However, an effective stimulation of megakaryocytopoiesis in vivo, bringing about an increase in the levels of blood platelets, may require interaction of rGM-CSF with other cytokines.