Effect of IFN-alpha on normal human hematopoiesis: an immunohistochemical and morphometric study on trephine biopsy specimens

Viral abrogation of stem cell transplantation tolerance causes graft rejection and host death by different mechanisms

Tolerance-based stem cell transplantation using sublethal conditioning is being considered for the treatment of human disease, but safety and efficacy remain to be established. We have shown that mouse bone marrow recipients treated with sublethal irradiation plus transient blockade of the CD40-CD154 costimulatory pathway develop permanent hematopoietic chimerism across allogeneic barriers. We now report that infection with lymphocytic choriomeningitis virus at the time of transplantation prevented engraftment of allogeneic, but not syngeneic, bone marrow in similarly treated mice. Infected allograft recipients also failed to clear the virus and died. Postmortem study revealed hypoplastic bone marrow and spleens. The cause of death was virus-induced IFN-alphabeta. The rejection of allogeneic bone marrow was mediated by a radioresistant CD8(+)TCR-alphabeta(+)NK1.1(-) T cell population. We conclude that a noncytopathic viral infection at the time of transplantation can prevent engraftment of allogeneic bone marrow and result in the death of sublethally irradiated mice treated with costimulation blockade. Clinical application of stem cell transplantation protocols based on costimulation blockade and tolerance induction may require patient isolation to facilitate the procedure and to protect recipients.

Direct signal transduction via functional interferon-alphabeta receptors in CD34+ hematopoietic stem cells

Affinity purified, freshly isolated CD34+ progenitors were shown to express low levels of type I interferon (IFN) receptors (740 +/- 60 binding sites/cell, K(d) 0.7 +/- 0.04 nM) determined by Scatchard's analysis using a radiolabelled, neutralizing, monoclonal antibody directed against the IFNAR1 chain of the human type I IFN receptor. Treatment of freshly isolated (day 0), highly purified (>95% pure) CD34+ cells with recombinant IFN-alpha resulted in rapid tyrosine phosphorylation and activation of STAT1, Tyk2 and JAK1 as shown by Western immunoblotting. Similarly, IFN treatment was shown by confocal microscopy to result in rapid nuclear localization of the transcription factors IRF1 and STAT2, demonstrating the presence of functional IFN receptors on freshly isolated (day 0) CD34+ cells. The number of specific type I IFN receptor binding sites expressed on hematopoietic progenitor cells increased to some 1440 +/- 40 per cell after 11 days of cultivation of CD34+ cells in vitrosuggesting that receptor expression increases with cell differentiation. IFN-mediated signal transduction and the inhibitory effect of IFN-alpha on 7 or 14 days CFU-GM and BFU-E colony formation was abrogated in the presence of the anti-IFNAR1 mAb, indicating that IFN-alpha acts directly on the proliferation of human hematopoietic progenitor cells via receptor activated signal transduction without excluding the induction of other cytokines or growth factors by residual accessory cells.

Bone marrow features improve prognostic efficiency in multivariate risk classification of chronic-phase Ph(1+) chronic myelogenous leukemia: a multicenter trial

PURPOSE

Multivariate risk classifications for chronic (stable)-phase Ph(1+) chronic myelogenous leukemia (CML) are generally focused on hematologic variables, and the putative prognostic property of bone morphology has been neglected or even contested so far.

PATIENTS AND METHODS

A total of 510 consecutively recruited patients in first chronic phase Ph(1+) CML and pretreatment bone marrow biopsy specimens were entered onto this multicenter observational trial to evaluate the effect of bone marrow histopathology. According to generally accepted criteria, patients with any signs of accelerated disease were excluded. Treatment modalities included administration of interferon alfa-2b (IFN) and chemotherapy with hydroxyurea (HU) or busulfan. Immunohistochemical and morphometric techniques were applied to identify marrow cells and to quantify fiber density. Patients were separated into learning and validation samples, and classification and regression tree (CART) analysis was performed to establish a prognostic decision tree.

RESULTS

CART analysis of the validation sample (123 patients with HU therapy) revealed the amount of erythroid precursors in the bone marrow, myelofibrosis, and splenomegaly as the most important prognostic features. Three risk profiles with significantly different survival patterns were established, with median survival times ranging from 33 to 108 months (two-sided log-rank test, P =.0001). The new score was confirmed by application to the learning sample with IFN therapy (two-sided log-rank test, P =.0002). Furthermore, risk status defined by the new score was significantly correlated with the occurrence of blast transformation.

CONCLUSION

Our data strongly implicate that prognostic classification of chronic-phase Ph(1+) CML can be significantly improved by the inclusion of morphologic parameters. The variables of the presented scoring system may be easily assessed by routinely processed aspirates and bone marrow trephines.

Interferon alpha2b directly induces fibroblast proliferation and transforming growth factor beta secretion of macrophages

To elucidate the effects of interferon alpha2b (IFN-alpha) on normal human bone marrow, fibroblasts from patients without haematopoietic pathology were cultivated and used in stimulation experiments. Further, co-cultures with highly enriched fractions of megakaryocytes and bone marrow macrophages were analysed. In this context, the influence of cell-to-cell interactions and humoral factors was determined in transwell and neutralization studies. Finally, secretion of platelet-derived growth factor (PDGF) and transforming growth factor beta1 (TGF-beta1) by single megakaryocytes and macrophages was examined by using the reverse haemolytic plaque assay (RHPA). Following these experimental designs, a direct proliferative activity of IFN-alpha on bone marrow fibroblasts could be demonstrated. In the unstimulated co-cultures, the megakaryocyte- but not the macrophage-enriched fraction induced fibroblast growth and [3H]-thymidine uptake. This effect was dependent on cell-to-cell contact and also on the influence of TGF-beta and PDGF. In the megakaryocyte-enriched co-cultures, the fibroblast proliferation was not altered by IFN-alpha, but in the macrophage fibroblast cultures addition of IFN-alpha enhanced fibroblast growth and [3H]-thymidine uptake was distinctively higher than in the monocultures. This effect was not obvious in the transwell or neutralization experiments. Finally, IFN-alpha treatment exerted a significantly elevated TGF-beta1 secretion in single macrophages. Our findings are in keeping with the assumption that several pathomechanisms participate in IFN-alpha-induced myelofibrosis, including direct and indirect effects.

Effects of interferon and hydroxyurea on bone marrow fibrosis in chronic myelogenous leukaemia: a comparative retrospective multicentre histological and clinical study

A retrospective multicentre clinicopathological study was performed on sequential bone marrow trephine biopsies in 100 patients with Ph1+-chronic myelogenous leukaemia (CML) to elucidate the effect of interferon (IFN) alpha 2b and hydroxyurea (HU) treatment on myelofibrosis and megakaryopoiesis. According to strictly defined therapeutic regimens, 38 patients received IFN as monotherapy, 23 patients a combination of IFN and HU and 39 patients HU only. Using standardized intervals of biopsies and histochemical and morphometric methods, a significant increase in reticulin fibre density and in the number of CD61+ megakaryocytes was detectable in the majority of IFN-treated patients. To a lesser degree, these changes were also expressed in the cohort with a combined IFN and HU regimen. In contrast to these findings, in the group of patients with HU as single-agent treatment, a stable state or reversal of myelofibrosis was detectable together with corresponding changes in megakaryopoiesis. Further evaluations revealed that these effects had occurred within the first year, mostly after 6 months of treatment, and were prominently expressed in those patients with a slight to relevant grade of myelofibrosis at presentation. In conclusion, this study provides persuasive evidence that monotherapy by IFN exerts a fibrogenic effect, while HU treatment seems to prevent and even resolves bone marrow fibrosis in CML. Probably, in relation to the complex pathomechanisms responsible for the generation of myelofibrosis, the changing content of reticulin fibres was usually accompanied by corresponding alterations in the number of CD61+ megakaryocytes, including atypical microforms and precursor cells.