Limits...
Extramedullary myelopoiesis in malaria depends on mobilization of myeloid-restricted progenitors by IFN-γ induced chemokines.

Belyaev NN, Biró J, Langhorne J, Potocnik AJ - PLoS Pathog. (2013)

Bottom Line: De-activation of IFN-γ signaling completely abrogated the contraction of BM myeloid progenitors.Systemic IFN-γ triggered the secretion of C-C motif ligand chemokines CCL2 and CCL7 leading to the egress of early, myeloid-committed progenitors from the bone marrow mediated by their common receptor CCR2.The mobilization of myeloid progenitors initiated extramedullary myelopoiesis in the spleen in a CCR2-dependent manner resulting in augmented myelopoiesis during acute malaria.

View Article: PubMed Central - PubMed

Affiliation: Division of Molecular Immunology, MRC National Institute for Medical Research, London, United Kingdom.

ABSTRACT
Resolution of a variety of acute bacterial and parasitic infections critically relies on the stimulation of myelopoiesis leading in cases to extramedullary hematopoiesis. Here, we report the isolation of the earliest myeloid-restricted progenitors in acute infection with the rodent malaria parasite, Plasmodium chabaudi. The rapid disappearance of these infection-induced myeloid progenitors from the bone marrow (BM) equated with contraction of the functional myeloid potential in that organ. The loss of BM myelopoiesis was not affected by the complete genetic inactivation of toll-like receptor signaling. De-activation of IFN-γ signaling completely abrogated the contraction of BM myeloid progenitors. Radiation chimeras of Ifngr1- and control BM revealed that IFN-γ signaling in an irradiation-resistant stromal compartment was crucial for the loss of early myeloid progenitors. Systemic IFN-γ triggered the secretion of C-C motif ligand chemokines CCL2 and CCL7 leading to the egress of early, myeloid-committed progenitors from the bone marrow mediated by their common receptor CCR2. The mobilization of myeloid progenitors initiated extramedullary myelopoiesis in the spleen in a CCR2-dependent manner resulting in augmented myelopoiesis during acute malaria. Consistent with the lack of splenic myelopoiesis in the absence of CCR2 we observed a significant persistence of parasitemia in malaria infected CCR2-deficient hosts. Our findings reveal how the activated immune system mobilizes early myeloid progenitors out of the BM thereby transiently establishing myelopoiesis in the spleen in order to contain and resolve the infection locally.

Show MeSH

Related in: MedlinePlus

IFN-γ in vitro effectively upregulates Sca-1 on HPCs without affecting expression of CD27.A. FACS-purified steady-state HPC were cultured in various concentration of IFN-γ for 24 hrs in vitro. Representative histograms from three experiments are depicted. B. CMPs, GMP, MEP were FACS-purified from steady state HPCs and stained for expression of CD27 before (post sort, red line shows “fluorescence minus one” FMO control) and after culture with IFN-γ for 24 hrs. Histograms from one of two experiments are shown.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3675198&req=5

ppat-1003406-g002: IFN-γ in vitro effectively upregulates Sca-1 on HPCs without affecting expression of CD27.A. FACS-purified steady-state HPC were cultured in various concentration of IFN-γ for 24 hrs in vitro. Representative histograms from three experiments are depicted. B. CMPs, GMP, MEP were FACS-purified from steady state HPCs and stained for expression of CD27 before (post sort, red line shows “fluorescence minus one” FMO control) and after culture with IFN-γ for 24 hrs. Histograms from one of two experiments are shown.

Mentions: Next we investigated the effect of IFN-γ on FACS-purified HPCs in vitro. After short-term culture (24 hrs) virtually all recovered HPCs upregulated Sca-1 to various extents (Figure 2A, upper panel). There was a biphasic expression of Sca-1 on HPCs, which was dependent on the concentration of exogenous IFN-γ added (Figure 2A, lower panel). These results clearly demonstrated that IFN-γ signaling in vivo and in vitro is both necessary and sufficient for the upregulation of Sca-1. Considering that the HPCs under homeostatic conditions are Sca-1 negative the upregulation of this antigen during infection or in vitro culture of HPCs with IFN-γ creates a problem for the analysis of stem cells and early progenitor subsets in infection. We therefore tested a panel of surface markers on pre-immune BM progenitor subsets and determined whether their expression was regulated by IFN-γ in vitro. We isolated HPCs and further subdivided this compartment into the common myeloid progenitor (CMP, CD34+ CD16/32lo/neg), the granulocyte monocyte progenitor (GMP, CD34+ CD16/32hi) and the megakaryocyte erythroid progenitor (MEP, CD34− CD16/32lo/neg), with the CMP containing a common myelo-erythroid progenitor pool [18]. Among the markers analyzed, CD27 is reportedly expressed on all myeloid BM progenitors [19] and was present ex vivo on all GMPs, a large fraction of CMPs, but virtually no MEPs (Figure 2B, middle panel). After short-term culture with IFN-γ we observed no change of CD27 expression on GMPs and most CMPs but a selective disappearance of CD27− cells from the CMP pool (Figure 2B, lower panel). The common progenitor for megakaryocytes and erythroid cells (MEP) was particular sensitive to IFN-γ treatment and underwent partially apoptosis, which also might explain the reduction of CD27− cells in the CMP cultures. Taken together, these results suggest that CD27 expression on myeloid progenitors is not modulated by IFN-γ in vitro and reliably distinguished myeloid progenitors from MEPs.


Extramedullary myelopoiesis in malaria depends on mobilization of myeloid-restricted progenitors by IFN-γ induced chemokines.

Belyaev NN, Biró J, Langhorne J, Potocnik AJ - PLoS Pathog. (2013)

IFN-γ in vitro effectively upregulates Sca-1 on HPCs without affecting expression of CD27.A. FACS-purified steady-state HPC were cultured in various concentration of IFN-γ for 24 hrs in vitro. Representative histograms from three experiments are depicted. B. CMPs, GMP, MEP were FACS-purified from steady state HPCs and stained for expression of CD27 before (post sort, red line shows “fluorescence minus one” FMO control) and after culture with IFN-γ for 24 hrs. Histograms from one of two experiments are shown.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3675198&req=5

ppat-1003406-g002: IFN-γ in vitro effectively upregulates Sca-1 on HPCs without affecting expression of CD27.A. FACS-purified steady-state HPC were cultured in various concentration of IFN-γ for 24 hrs in vitro. Representative histograms from three experiments are depicted. B. CMPs, GMP, MEP were FACS-purified from steady state HPCs and stained for expression of CD27 before (post sort, red line shows “fluorescence minus one” FMO control) and after culture with IFN-γ for 24 hrs. Histograms from one of two experiments are shown.
Mentions: Next we investigated the effect of IFN-γ on FACS-purified HPCs in vitro. After short-term culture (24 hrs) virtually all recovered HPCs upregulated Sca-1 to various extents (Figure 2A, upper panel). There was a biphasic expression of Sca-1 on HPCs, which was dependent on the concentration of exogenous IFN-γ added (Figure 2A, lower panel). These results clearly demonstrated that IFN-γ signaling in vivo and in vitro is both necessary and sufficient for the upregulation of Sca-1. Considering that the HPCs under homeostatic conditions are Sca-1 negative the upregulation of this antigen during infection or in vitro culture of HPCs with IFN-γ creates a problem for the analysis of stem cells and early progenitor subsets in infection. We therefore tested a panel of surface markers on pre-immune BM progenitor subsets and determined whether their expression was regulated by IFN-γ in vitro. We isolated HPCs and further subdivided this compartment into the common myeloid progenitor (CMP, CD34+ CD16/32lo/neg), the granulocyte monocyte progenitor (GMP, CD34+ CD16/32hi) and the megakaryocyte erythroid progenitor (MEP, CD34− CD16/32lo/neg), with the CMP containing a common myelo-erythroid progenitor pool [18]. Among the markers analyzed, CD27 is reportedly expressed on all myeloid BM progenitors [19] and was present ex vivo on all GMPs, a large fraction of CMPs, but virtually no MEPs (Figure 2B, middle panel). After short-term culture with IFN-γ we observed no change of CD27 expression on GMPs and most CMPs but a selective disappearance of CD27− cells from the CMP pool (Figure 2B, lower panel). The common progenitor for megakaryocytes and erythroid cells (MEP) was particular sensitive to IFN-γ treatment and underwent partially apoptosis, which also might explain the reduction of CD27− cells in the CMP cultures. Taken together, these results suggest that CD27 expression on myeloid progenitors is not modulated by IFN-γ in vitro and reliably distinguished myeloid progenitors from MEPs.

Bottom Line: De-activation of IFN-γ signaling completely abrogated the contraction of BM myeloid progenitors.Systemic IFN-γ triggered the secretion of C-C motif ligand chemokines CCL2 and CCL7 leading to the egress of early, myeloid-committed progenitors from the bone marrow mediated by their common receptor CCR2.The mobilization of myeloid progenitors initiated extramedullary myelopoiesis in the spleen in a CCR2-dependent manner resulting in augmented myelopoiesis during acute malaria.

View Article: PubMed Central - PubMed

Affiliation: Division of Molecular Immunology, MRC National Institute for Medical Research, London, United Kingdom.

ABSTRACT
Resolution of a variety of acute bacterial and parasitic infections critically relies on the stimulation of myelopoiesis leading in cases to extramedullary hematopoiesis. Here, we report the isolation of the earliest myeloid-restricted progenitors in acute infection with the rodent malaria parasite, Plasmodium chabaudi. The rapid disappearance of these infection-induced myeloid progenitors from the bone marrow (BM) equated with contraction of the functional myeloid potential in that organ. The loss of BM myelopoiesis was not affected by the complete genetic inactivation of toll-like receptor signaling. De-activation of IFN-γ signaling completely abrogated the contraction of BM myeloid progenitors. Radiation chimeras of Ifngr1- and control BM revealed that IFN-γ signaling in an irradiation-resistant stromal compartment was crucial for the loss of early myeloid progenitors. Systemic IFN-γ triggered the secretion of C-C motif ligand chemokines CCL2 and CCL7 leading to the egress of early, myeloid-committed progenitors from the bone marrow mediated by their common receptor CCR2. The mobilization of myeloid progenitors initiated extramedullary myelopoiesis in the spleen in a CCR2-dependent manner resulting in augmented myelopoiesis during acute malaria. Consistent with the lack of splenic myelopoiesis in the absence of CCR2 we observed a significant persistence of parasitemia in malaria infected CCR2-deficient hosts. Our findings reveal how the activated immune system mobilizes early myeloid progenitors out of the BM thereby transiently establishing myelopoiesis in the spleen in order to contain and resolve the infection locally.

Show MeSH
Related in: MedlinePlus