A Secreted Proform of Neutrophil Proteinase 3 Regulates the Proliferation of Granulopoietic Progenitor Cells

Blood ◽  
1999 ◽  
Vol 93 (3) ◽  
pp. 849-856 ◽  
Author(s):  
Stefan Sköld ◽  
Bodil Rosberg ◽  
Urban Gullberg ◽  
Tor Olofsson
Keyword(s):  
Amino Acid ◽  
Progenitor Cells ◽  
Inhibitory Activity ◽  
Inhibitory Effect ◽  
S Phase ◽  
Cathepsin G ◽  
Proteinase 3 ◽  
Amino Acid Sequencing ◽  
Granulopoietic Progenitor Cells ◽  
Marrow Cells

Abstract Myeloid leukemia cells, the human promyelocytic cell line HL-60, and a subpopulation of normal marrow cells produce a leukemia-associated inhibitor (LAI) that reversibly downmodulates DNA synthesis of normal granulopoietic progenitor cells colony-forming unit granulocyte-macrophage (CFU-GM). We isolated an active 125-kD component of LAI from HL-60 conditioned medium (CM), subjected it to cyanogen bromide cleavage and show by amino acid sequencing of the resulting peptides that it consists of a complex of the serine proteinase inhibitor 1-antitrypsin and a 31-kD fragment that retained the S-phase inhibitory activity, but resisted sequencing. This finding suggested that the 31-kD fragment originated from one of the neutrophil serine proteases (ie, elastase, proteinase 3, or cathepsin G) produced by normal promyelocytes, as well as HL-60 cells, for storage in primary granules and partly secreted during synthesis as enzymatically inactive proforms. Immunoblot analysis showed that the 125-kD complex contained proteinase 3 (PR3), and immunoprecipitation of PR3 from HL-60 CM abrogated the S-phase inhibitory activity, whereas immunoprecipitation of cathepsin G or elastase did not. Immunoprecipitation of PR3 from CM of a subpopulation of normal marrow cells also abrogated the S-phase inhibitory effect. Furthermore, CM from rat RBL and murine 32D cell lines transfected with human PR3 both reduced the fraction of CFU-GM in S-phase with 30% to 80% at 1 to 35 ng/mL PR3, whereas CM of the same cells transfected with cathepsin G or elastase did not. Also, an enzymatically silent mutant of PR3 exerted full activity, showing that the S-phase modulatory effect is not dependent on proteolytic activity. Amino acid sequencing of biosynthetically radiolabeled PR3 showed that PR3 from transfected cells is secreted after synthesis as proforms retaining amino terminal propeptides. In contrast, mature PR3 extracted from mature neutrophils has only minor activity. The inhibitory effect of secreted PR3 is reversible and abrogated by granulocyte (G)- or granulocyte-macrophage colony-stimulating factor (GM-CSF). Experiments with highly purified CD34+ bone marrow cells suggested that PR3 acts directly on the granulopoietic progenitor cells. These observations suggest a role for PR3 in regulation of granulopoiesis, and possibly in suppression of normal granulopoiesis in leukemia.

A Secreted Proform of Neutrophil Proteinase 3 Regulates the Proliferation of Granulopoietic Progenitor Cells

Blood ◽  
1999 ◽  
Vol 93 (3) ◽  
pp. 849-856 ◽  
Author(s):  
Stefan Sköld ◽  
Bodil Rosberg ◽  
Urban Gullberg ◽  
Tor Olofsson
Keyword(s):  
Amino Acid ◽  
Progenitor Cells ◽  
Inhibitory Activity ◽  
Inhibitory Effect ◽  
S Phase ◽  
Cathepsin G ◽  
Proteinase 3 ◽  
Amino Acid Sequencing ◽  
Granulopoietic Progenitor Cells ◽  
Marrow Cells

Myeloid leukemia cells, the human promyelocytic cell line HL-60, and a subpopulation of normal marrow cells produce a leukemia-associated inhibitor (LAI) that reversibly downmodulates DNA synthesis of normal granulopoietic progenitor cells colony-forming unit granulocyte-macrophage (CFU-GM). We isolated an active 125-kD component of LAI from HL-60 conditioned medium (CM), subjected it to cyanogen bromide cleavage and show by amino acid sequencing of the resulting peptides that it consists of a complex of the serine proteinase inhibitor 1-antitrypsin and a 31-kD fragment that retained the S-phase inhibitory activity, but resisted sequencing. This finding suggested that the 31-kD fragment originated from one of the neutrophil serine proteases (ie, elastase, proteinase 3, or cathepsin G) produced by normal promyelocytes, as well as HL-60 cells, for storage in primary granules and partly secreted during synthesis as enzymatically inactive proforms. Immunoblot analysis showed that the 125-kD complex contained proteinase 3 (PR3), and immunoprecipitation of PR3 from HL-60 CM abrogated the S-phase inhibitory activity, whereas immunoprecipitation of cathepsin G or elastase did not. Immunoprecipitation of PR3 from CM of a subpopulation of normal marrow cells also abrogated the S-phase inhibitory effect. Furthermore, CM from rat RBL and murine 32D cell lines transfected with human PR3 both reduced the fraction of CFU-GM in S-phase with 30% to 80% at 1 to 35 ng/mL PR3, whereas CM of the same cells transfected with cathepsin G or elastase did not. Also, an enzymatically silent mutant of PR3 exerted full activity, showing that the S-phase modulatory effect is not dependent on proteolytic activity. Amino acid sequencing of biosynthetically radiolabeled PR3 showed that PR3 from transfected cells is secreted after synthesis as proforms retaining amino terminal propeptides. In contrast, mature PR3 extracted from mature neutrophils has only minor activity. The inhibitory effect of secreted PR3 is reversible and abrogated by granulocyte (G)- or granulocyte-macrophage colony-stimulating factor (GM-CSF). Experiments with highly purified CD34+ bone marrow cells suggested that PR3 acts directly on the granulopoietic progenitor cells. These observations suggest a role for PR3 in regulation of granulopoiesis, and possibly in suppression of normal granulopoiesis in leukemia.

scholarly journals OXA-48-Mediated Ceftazidime-Avibactam Resistance Is Associated with Evolutionary Trade-Offs

mSphere ◽  
2019 ◽  
Vol 4 (2) ◽  
Author(s):  
Christopher Fröhlich ◽  
Vidar Sørum ◽  
Ane Molden Thomassen ◽  
Pål Jarle Johnsen ◽  
Hanna-Kirsti S. Leiros ◽  
...  
Keyword(s):  
Amino Acid ◽  
Inhibitory Activity ◽  
Treatment Options ◽  
Inhibitory Effect ◽  
Amino Acid Substitutions ◽  
Gram Negative ◽  
Content Type ◽  
Mortality And Morbidity ◽  
Trade Offs ◽  
Collateral Effects

ABSTRACTInfections due to carbapenemase-producing Gram-negative pathogens are associated with limited treatment options and consequently lead to increased mortality and morbidity. In response, combinations of existing β-lactams and novel β-lactamase inhibitors, such as ceftazidime-avibactam (CAZ-AVI), have been developed as alternative treatment options. To understand the development of resistance and evolutionary trajectories under CAZ-AVI exposure, we studied the effects of ceftazidime (CAZ) and CAZ-AVI on the carbapenemase OXA-48 and the epidemic OXA-48 plasmid inEscherichia coli. Exposure of CAZ and CAZ-AVI resulted in single (P68A) and double (P68A,Y211S) amino acid substitutions in OXA-48, respectively. The antimicrobial susceptibility data and enzyme kinetics showed that the P68A substitution was responsible for an increased activity toward CAZ, whereas P68A,Y211S led to a decrease in the inhibitory activity of AVI. X-ray crystallography and molecular modeling of the mutants demonstrated increased flexibility within the active site, which could explain the elevated CAZ hydrolysis and reduced inhibitory activity of AVI. Interestingly, these substitutions resulted in collateral effects compromising the activity of OXA-48 toward carbapenems and penicillins. Moreover, exposure to CAZ-AVI selected for mutations within the OXA-48-encoding plasmid that severely reduced fitness in the absence of antimicrobial selection. These evolutionary trade-offs may contribute to limit the evolution of OXA-48-mediated CAZ and CAZ-AVI resistance, as well as potentially resensitize isolates toward other therapeutic alternatives.IMPORTANCEThe recent introduction of novel β-lactam/β-lactamase inhibitor combinations like ceftazidime-avibactam has increased our ability to treat infections caused by multidrug-resistant Gram-negative bacteria, including carbapenemase-producingEnterobacterales. However, the increasing number of cases of reported resistance to ceftazidime-avibactam is a concern. OXA-48 is a carbapenemase that has no significant effect on ceftazidime, but is inhibited by avibactam. Since isolates with OXA-48 frequently harbor extended-spectrum β-lactamases that are inhibited by avibactam, it is likely that ceftazidime-avibactam will be used to treat infections caused by OXA-48-producingEnterobacterales.Our data show that exposure to ceftazidime-avibactam can lead to changes in OXA-48, resulting in increased ability to hydrolyze ceftazidime and withstand the inhibitory effect of avibactam. Thus, resistance toward ceftazidime-avibactam among OXA-48-producingEnterobacteralesshould be monitored. Interestingly, the compromising effect of the amino acid substitutions in OXA-48 on other β-lactams and the effect of ceftazidime-avibactam exposure on the epidemic OXA-48 plasmid indicate that the evolution of ceftazidime-avibactam resistance comes with collateral effects.

scholarly journals Effect of recombinant interferons alpha and gamma on human bone marrow- derived megakaryocytic progenitor cells

Blood ◽  
1987 ◽  
Vol 70 (4) ◽  
pp. 1173-1179 ◽  
Author(s):  
A Ganser ◽  
C Carlo-Stella ◽  
J Greher ◽  
B Volkers ◽  
D Hoelzer
Keyword(s):  
Bone Marrow ◽  
T Lymphocytes ◽  
Progenitor Cells ◽  
Inhibitory Activity ◽  
Bone Marrow Cells ◽  
Suppressive Effect ◽  
Inhibitory Effect ◽  
Hematopoietic Progenitor Cells ◽  
Adherent Cells ◽  
Hematopoietic Progenitor

Abstract Interferons (IFNs) have been shown to suppress the proliferation of human pluripotent hematopoietic progenitor cells, CFU-GEMM, and committed erythroid (BFU-E, CFU-E) and granulocyte-macrophage (CFU-GM) progenitor cells. However, no information is yet available concerning the effect of IFNs on human megakaryocytic progenitor cells CFU-Mk. Furthermore the mechanisms underlying the inhibitory activity of IFNs are still controversial. Therefore highly purified recombinant IFN preparations, rIFN-alpha and rIFN-gamma, were assessed for their influence on in vitro growth of human bone marrow-derived CFU-Mk as well as CFU-GEMM. In addition, the role of hematopoietic accessory cells, that is, adherent cells and T lymphocytes, in the mediation of the suppressive effect of rIFNs was examined. When added to unseparated bone marrow cells, both rIFN preparations significantly inhibited colony formation with 50% inhibition of CFU-Mk occurring at 22 U/mL for rIFN-alpha and 59 U/mL for rIFN-gamma, while 50% inhibition of CFU-GEMM occurred at 59 U/mL for rIFN-alpha and 101 U/mL for rIFN-gamma. The suppressive effect of rIFN-alpha and rIFN-gamma was selectively abolished by monoclonal antibodies (MoAbs) against rIFN-alpha and rIFN- gamma, thus confirming that the inhibitory activity was due to the rIFN preparations used. The antiproliferative effect of rIFN-alpha and rIFN- gamma on CFU-GEMM growth was not associated with a decrease in the percentage of mixed colonies containing megakaryocytic cells as assessed by use of the MoAb C17.28 against platelet glycoprotein IIIa. Removal of adherent cells and T lymphocytes from the target bone marrow cells had no influence on the suppressive effect of rIFN-alpha, whereas it significantly reduced the inhibitory effect of rIFN-gamma on the growth of megakaryocytic colonies and the other hematopoietic progenitors. The data indicate that (1) human megakaryocytopoiesis is markedly inhibited by rIFN-alpha and rIFN-gamma, and (2) the inhibitory effect of rIFN-alpha is due to a direct action on hematopoietic progenitor cells, whereas the effect of rIFN-gamma is mediated to a significant degree through accessory cell populations.

Multilineage Expansion of Lymphoid and Myeloid Cells in Mice Expressing PML-RARα under the Control of the Murine Cathepsin G Locus.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2551-2551
Author(s):  
Geoffrey L. Uy ◽  
Jacqueline E. Payton ◽  
Timothy James Ley
Keyword(s):  
Gene Expression ◽  
Bone Marrow ◽  
T Cells ◽  
Stem Cell ◽  
Progenitor Cells ◽  
Cell Function ◽  
Cathepsin G ◽  
Pcr Analysis ◽  
Self Renewal ◽  
Marrow Cells

In one of our laboratory’s models of acute promyelocytic leukemia (APL), the PML-RARα fusion cDNA is knocked into the 5′ UT of the azurophil granule protease, cathepsin G. Nearly all mCG-PML-RARα mice develop lethal leukemia with promyelocytic features following a 150–400 day latent period. We originally chose the cathepsin G gene for the targeting locus because its expression was believed to be restricted to promyelocytes. However, we have now observed high levels of cathepsin G expression with gene expression profiling of leukemic bone marrow samples from patients with AML FAB M1 or M2, i.e. blasts with minimal or no differentiation (M1: n=21, mean raw expression value for cathepsin G=23,885 ± 31,737; M2: n=22, mean=24,088 ± 26,585; M3: n=14, mean 116,029 ± 47,017). To examine whether cathepsin G is normally expressed in murine hematopoietic progenitor cells, we performed gene expression arrays with highly purified Sca-1+/lin− bone marrow cells; cathepsin G mRNA was easily detected in these cells (n=4, mean cathepsin G raw expression value=9,324 ± 5,082; array average normalized to 1,500). We therefore decided to determine whether the early progenitor compartment in mCG-PML-RARα mice was expanded due to unexpected expression of the transgene in KLS (c-kit+, Lin−, Sca-1+) cells; however, no difference was detected in the frequency of marrow-derived KLS cells between mCG-PML-RARα and WT mice that were age, strain, and gender matched (0.074% vs 0.071%, p=0.89). The GMP compartment (Lin−, c-kit+, Sca1−, CD34+, FcRγ+) showed a tendency towards expansion in mCG-PML-RARα mice (0.10% vs 0.032%) but the difference was not significant (p=0.067). To better assess stem cell function in these mice, we performed a competitive repopulation study using marrow derived from Ly 5.2/mCG-PML-RARα mice mixed with Ly5.1/WT marrow cells at various ratios (1:1, 9:1, and 1:9) that were transplanted into genetically compatible hosts. Lineage markers in the peripheral blood were tested at 6, 12, and 24 weeks to assess the contribution of mCG-PML-RARα-derived progenitor and stem cells to the B, T, and myeloid lineages. As expected, we observed a highly reproducible increase in the proportion of Gr-1+ cells derived from mCG-PML-RARα donors at all time points (78.8% ± 11% donor-derived cells at a 1:1 donor: recipient ratio at 6 months, p=0.0006). Surprisingly, we also observed a reproducible increase in B220+/CD19+ cells (66.7% ± 4%, p<0.0001) and CD3+ cells from the mCG-PML-RARα donors (60.4% ± 3% p=0.0010) at 6 months, suggesting that mCG-PML-RARα also confers a growth or survival advantage to B and T cells. To determine whether cathepsin G was expressed in these compartments, we purified CD19+ B and CD3+ T cells by flow cytometry (>99% purity) and did not detect cathepsin G mRNA using a sensitive, knockout-proven qRT-PCR analysis. These data strongly suggest that both the WT cathepsin G gene and the mutant mCG-PML-RARα allele are unexpectedly expressed in the stem cell compartment, with both myeloid and lymphoid progeny of these cells displaying a growth advantage in vivo. However, lymphoid malignancies have not been detected in these mice (n>400), suggesting that PML-RARα is unable to initiate transformation in lymphocytes. Our data imply that the PML-RARα gene is activated in a multipotent compartment in this mouse model, raising the possibility that PML-RARα may not actually ‘reprogram’ progenitor cells to undergo self-renewal, but may rather initiate transformation in pluripotent cells with intrinsic self-renewal capabilities.

scholarly journals Abnormal responses of myeloid progenitor cells to recombinant human colony-stimulating factors in congenital neutropenia

Blood ◽  
1990 ◽  
Vol 75 (11) ◽  
pp. 2143-2149 ◽  
Author(s):  
M Kobayashi ◽  
C Yumiba ◽  
Y Kawaguchi ◽  
Y Tanaka ◽  
K Ueda ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Bone Marrow Cells ◽  
Normal Subjects ◽  
Inhibitory Effect ◽  
Congenital Neutropenia ◽  
Agar Culture ◽  
Myeloid Progenitor ◽  
Myeloid Progenitor Cells ◽  
Marrow Cells

Abstract The effects of recombinant human interleukin-3 (IL-3) and recombinant human granulocyte colony-stimulating factor (G-CSF) on the growth of myeloid progenitor cells (CFU-C) in semisolid agar culture were studied in two patients with Kostmann-type congenital neutropenia. CFU-C growth in bone marrow cells from patients was significantly reduced in response to various concentrations of either IL-3 or G-CSF alone, compared with that from normal subjects. There was no inhibitory effect of bone marrow cells from patients on normal CFU-C formation supported by IL-3 or G-CSF. However, the simultaneous stimulation with IL-3 and G- CSF induced the increase of CFU-C formation in patients with congenital neutropenia. Furthermore, CFU-C growth in both patients was supported when bone marrow cells were preincubated with IL-3 in liquid culture followed by the stimulation with G-CSF in semisolid agar culture. In contrast, that was not supported by the preincubation with G-CSF and the subsequent stimulation with IL-3. This evidence suggests that the hematopoietic progenitor cells in patients with congenital neutropenia have the potential for developing CFU-C in the combined stimulation with IL-3 and G-CSF, and that this growth may be dependent on the priming of IL-3 followed by the stimulation with G-CSF. The level of mature neutrophils in peripheral blood was not fully restored to normal levels by the daily administration of G-CSF in doses of 100 to 200 micrograms/m2 of body surface area for 20 to 25 days in both patients. These observations raise the possibility that the combination of IL-3 and G-CSF might have a potential role for the increase of neutrophil counts in patients with congenital neutropenia.

scholarly journals HBV Pre-S1-Derived Myristoylated Peptide (Myr47): Identification of the Inhibitory Activity on the Cellular Uptake of Lipid Nanoparticles

Viruses ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 929
Author(s):  
Masaya Nanahara ◽  
Ya-Ting Chang ◽  
Masaharu Somiya ◽  
Shun’ichi Kuroda
Keyword(s):  
Amino Acid ◽  
Cellular Uptake ◽  
Inhibitory Activity ◽  
Sodium Taurocholate ◽  
Lipid Nanoparticles ◽  
Inhibitory Effect ◽  
Amino Acid Sequences ◽  
Hbv Infection ◽  
Dependent Manner ◽  
Independent Manner

The Myr47 lipopeptide, consisting of hepatitis B virus (HBV) pre-S1 domain (myristoylated 2–48 peptide), is an effective commercialized anti-HBV drug that prevents the interaction of HBV with sodium taurocholate cotransporting polypeptide (NTCP) on human hepatocytes, an activity which requires both N-myristoylation residue and specific amino acid sequences. We recently reported that Myr47 reduces the cellular uptake of HBV surface antigen (HBsAg, subviral particle of HBV) in the absence of NTCP expression. In this study, we analyzed how Myr47 reduces the cellular uptake of lipid nanoparticles (including liposomes (LPs) and HBsAg) without NTCP expression. By using Myr47 mutants lacking the HBV infection inhibitory activity, they could reduce the cellular uptake of LPs in an N-myristoylation-dependent manner and an amino acid sequence-independent manner, not only in human liver-derived cells but also in human non-liver-derived cells. Moreover, Myr47 and its mutants could reduce the interaction of LPs with apolipoprotein E3 (ApoE3) in an N-myristoylation-dependent manner regardless of their amino acid sequences. From these results, lipopeptides are generally anchored by inserting their myristoyl residue into the lipid bilayer and can inhibit the interaction of LPs/HBsAg with apolipoprotein, thereby reducing the cellular uptake of LPs/HBsAg. Similarly, Myr47 would interact with HBV, inhibiting the uptake of HBV into human hepatic cells, while the inhibitory effect of Myr47 may be secondary to its ability to protect against HBV infection.

scholarly journals Abnormal responses of myeloid progenitor cells to recombinant human colony-stimulating factors in congenital neutropenia

Blood ◽  
1990 ◽  
Vol 75 (11) ◽  
pp. 2143-2149 ◽  
Author(s):  
M Kobayashi ◽  
C Yumiba ◽  
Y Kawaguchi ◽  
Y Tanaka ◽  
K Ueda ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Bone Marrow Cells ◽  
Normal Subjects ◽  
Inhibitory Effect ◽  
Congenital Neutropenia ◽  
Agar Culture ◽  
Myeloid Progenitor ◽  
Myeloid Progenitor Cells ◽  
Marrow Cells

The effects of recombinant human interleukin-3 (IL-3) and recombinant human granulocyte colony-stimulating factor (G-CSF) on the growth of myeloid progenitor cells (CFU-C) in semisolid agar culture were studied in two patients with Kostmann-type congenital neutropenia. CFU-C growth in bone marrow cells from patients was significantly reduced in response to various concentrations of either IL-3 or G-CSF alone, compared with that from normal subjects. There was no inhibitory effect of bone marrow cells from patients on normal CFU-C formation supported by IL-3 or G-CSF. However, the simultaneous stimulation with IL-3 and G- CSF induced the increase of CFU-C formation in patients with congenital neutropenia. Furthermore, CFU-C growth in both patients was supported when bone marrow cells were preincubated with IL-3 in liquid culture followed by the stimulation with G-CSF in semisolid agar culture. In contrast, that was not supported by the preincubation with G-CSF and the subsequent stimulation with IL-3. This evidence suggests that the hematopoietic progenitor cells in patients with congenital neutropenia have the potential for developing CFU-C in the combined stimulation with IL-3 and G-CSF, and that this growth may be dependent on the priming of IL-3 followed by the stimulation with G-CSF. The level of mature neutrophils in peripheral blood was not fully restored to normal levels by the daily administration of G-CSF in doses of 100 to 200 micrograms/m2 of body surface area for 20 to 25 days in both patients. These observations raise the possibility that the combination of IL-3 and G-CSF might have a potential role for the increase of neutrophil counts in patients with congenital neutropenia.

Oxytocin analogues with inhibitory properties, containing in position 2 a hydrophobic amino acid of D-configuration

1985 ◽  
Vol 50 (1) ◽  
pp. 132-145 ◽  
Author(s):  
Michal Lebl ◽  
Tomislav Barth ◽  
Linda Servítová ◽  
Jiřina Slaninová ◽  
Karel Jošt
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Inhibitory Activity ◽  
Structural Features ◽  
Inhibitory Effect ◽  
Hydrophobic Amino Acid

Ten analogues derived from oxytocin, deamino-oxytocin and deamino-carba-oxytocin were prepared which contained a D-amino acid in the position 2 of the parent system. The following D-amino acids were introduced: tyrosine, phenylalanine, p-methylphenylalanine, p-ethylphenylalanine and O-ethyltyrosine. Combination of two structural features which alone lead to strong inhibitors (a suitable D-amino acid in position 2 and a penicillamine moiety in position 1) did not enhance the inhibitory effect. Compounds containing D-tyrosine are weak agonists in the uterotonic assay; in case of 1-carba-analogues they can be converted into sulfoxides with low inhibitory activity. Analogues with D-phenylalanine substituted in the para-position are the most potent antagonists of the uterotonic effect of oxytocin (pA2 = 8.73) in vitro.

scholarly journals Effect of recombinant interferons alpha and gamma on human bone marrow- derived megakaryocytic progenitor cells

Blood ◽  
1987 ◽  
Vol 70 (4) ◽  
pp. 1173-1179 ◽  
Author(s):  
A Ganser ◽  
C Carlo-Stella ◽  
J Greher ◽  
B Volkers ◽  
D Hoelzer
Keyword(s):  
Bone Marrow ◽  
T Lymphocytes ◽  
Progenitor Cells ◽  
Inhibitory Activity ◽  
Bone Marrow Cells ◽  
Suppressive Effect ◽  
Inhibitory Effect ◽  
Hematopoietic Progenitor Cells ◽  
Adherent Cells ◽  
Hematopoietic Progenitor

Interferons (IFNs) have been shown to suppress the proliferation of human pluripotent hematopoietic progenitor cells, CFU-GEMM, and committed erythroid (BFU-E, CFU-E) and granulocyte-macrophage (CFU-GM) progenitor cells. However, no information is yet available concerning the effect of IFNs on human megakaryocytic progenitor cells CFU-Mk. Furthermore the mechanisms underlying the inhibitory activity of IFNs are still controversial. Therefore highly purified recombinant IFN preparations, rIFN-alpha and rIFN-gamma, were assessed for their influence on in vitro growth of human bone marrow-derived CFU-Mk as well as CFU-GEMM. In addition, the role of hematopoietic accessory cells, that is, adherent cells and T lymphocytes, in the mediation of the suppressive effect of rIFNs was examined. When added to unseparated bone marrow cells, both rIFN preparations significantly inhibited colony formation with 50% inhibition of CFU-Mk occurring at 22 U/mL for rIFN-alpha and 59 U/mL for rIFN-gamma, while 50% inhibition of CFU-GEMM occurred at 59 U/mL for rIFN-alpha and 101 U/mL for rIFN-gamma. The suppressive effect of rIFN-alpha and rIFN-gamma was selectively abolished by monoclonal antibodies (MoAbs) against rIFN-alpha and rIFN- gamma, thus confirming that the inhibitory activity was due to the rIFN preparations used. The antiproliferative effect of rIFN-alpha and rIFN- gamma on CFU-GEMM growth was not associated with a decrease in the percentage of mixed colonies containing megakaryocytic cells as assessed by use of the MoAb C17.28 against platelet glycoprotein IIIa. Removal of adherent cells and T lymphocytes from the target bone marrow cells had no influence on the suppressive effect of rIFN-alpha, whereas it significantly reduced the inhibitory effect of rIFN-gamma on the growth of megakaryocytic colonies and the other hematopoietic progenitors. The data indicate that (1) human megakaryocytopoiesis is markedly inhibited by rIFN-alpha and rIFN-gamma, and (2) the inhibitory effect of rIFN-alpha is due to a direct action on hematopoietic progenitor cells, whereas the effect of rIFN-gamma is mediated to a significant degree through accessory cell populations.

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