Potent but transient immunosuppression of T-cells is a general feature of CD71+ erythroid cells

CD71+ erythroid cells (CECs) have been recently recognized in both neonates and cancer patients as potent immunoregulatory cells. Here, we show that in mice early-stage CECs expand in anemia, have high levels of arginase 2 (ARG2) and reactive oxygen species (ROS). In the spleens of anemic mice, CECs expansion-induced L-arginine depletion suppresses T-cell responses. In humans with anemia, CECs expand and express ARG1 and ARG2 that suppress T-cells IFN-γ production. Moreover, bone marrow CECs from healthy human donors suppress T-cells proliferation. CECs differentiated from peripheral blood mononuclear cells potently suppress T-cell activation, proliferation, and IFN-γ production in an ARG- and ROS-dependent manner. These effects are the most prominent for early-stage CECs (CD71highCD235adim cells). The suppressive properties disappear during erythroid differentiation as more differentiated CECs and mature erythrocytes lack significant immunoregulatory properties. Our studies provide a novel insight into the role of CECs in the immune response regulation.

Sex Matters: Physiological Abundance of Immuno-Regulatory CD71+ Erythroid Cells Impair Immunity in Females

Mature erythrocytes are the major metabolic regulators by transporting oxygen throughout the body. However, their precursors and progenitors defined as CD71+ Erythroid Cells (CECs) exhibit a wide range of immunomodulatory properties. Here, we uncover pronounced sexual dimorphism in CECs. We found female but not male mice, both BALB/c and C57BL/6, and human females were enriched with CECs. CECs, mainly their progenitors defined as CD45+CECs expressed higher levels of reactive oxygen species (ROS), PDL-1, VISTA, Arginase II and Arginase I compared to their CD45- counterparts. Consequently, CECs by the depletion of L-arginine suppress T cell activation and proliferation. Expansion of CECs in anemic mice and also post-menstrual cycle in women can result in L-arginine depletion in different microenvironments in vivo (e.g. spleen) resulting in T cell suppression. As proof of concept, we found that anemic female mice and mice adoptively transferred with CECs from anemic mice became more susceptible to Bordetella pertussis infection. These observations highlight the role of sex and anemia-mediated immune suppression in females. Notably, enriched CD45+CECs may explain their higher immunosuppressive properties in female BALB/c mice. Finally, we observed significantly more splenic central macrophages in female mice, which can explain greater extramedullary erythropoiesis and subsequently abundance of CECs in the periphery. Thus, sex-specific differences frequency in the frequency of CECs might be imprinted by differential erythropoiesis niches and hormone-dependent manner.

Blockade of IL-22 signaling reverses erythroid dysfunction in stress-induced anemias

Patients with myelodysplastic syndromes (MDSs) display severe anemia but the mechanisms underlying this phenotype are incompletely understood. Right open-reading-frame kinase 2 (RIOK2) encodes a protein kinase located at 5q15, a region frequently lost in patients with MDS del(5q). Here we show that hematopoietic cell-specific haploinsufficient deletion of Riok2 (Riok2f/+Vav1cre) led to reduced erythroid precursor frequency leading to anemia. Proteomic analysis of Riok2f/+Vav1cre erythroid precursors suggested immune system activation, and transcriptomic analysis revealed an increase in p53-dependent interleukin (IL)-22 in Riok2f/+Vav1cre CD4+ T cells (TH22). Further, we discovered that the IL-22 receptor, IL-22RA1, was unexpectedly present on erythroid precursors. Blockade of IL-22 signaling alleviated anemia not only in Riok2f/+Vav1cre mice but also in wild-type mice. Serum concentrations of IL-22 were increased in the subset of patients with del(5q) MDS as well as patients with anemia secondary to chronic kidney disease. This work reveals a possible therapeutic opportunity for reversing many stress-induced anemias by targeting IL-22 signaling.

Alterations in sialic-acid O-acetylation glycoforms during murine erythrocyte development

We used Casd1-deficient mice to confirm that this enzyme is responsible for 9-O-acetylation of sialic acids in vivo. We observed a complete loss of 9-O-acetylation of sialic acid on the surface of myeloid, erythroid and CD4+ T cells in Casd1-deficient mice. Although 9-O-acetylation of sialic acids on multiple hematopoietic lineages was lost, there were no obvious defects in hematopoiesis. Interestingly, erythrocytes from Casd1-deficient mice also lost reactivity to TER-119, a rat monoclonal antibody that is widely used to mark the murine erythroid lineage. The sialic acid glyco-epitope recognized by TER-119 on erythrocytes was sensitive to the sialic acid O-acetyl esterase activity of the hemagglutinin-esterase from bovine coronavirus but not to the corresponding enzyme from the influenza C virus. During erythrocyte development, TER-119+ Ery-A and Ery-B cells could be stained by catalytically inactive bovine coronavirus hemagglutinin-esterase but not by the inactive influenza C hemagglutinin-esterase, while TER-119+ Ery-C cells and mature erythrocytes were recognized by both virolectins. Although the structure of the sialoglycoconjugate recognized by TER-119 was not chemically demonstrated, its selective binding to virolectins suggests that it may be comprised of a 7,9-di-O-acetyl form of sialic acid. As erythrocytes mature, the surfaces of Ery-C cells and mature erythrocytes also acquire an additional distinct CASD1-dependent 9-O-acetyl sialic acid moiety that can be recognized by virolectins from both influenza C and bovine coronavirus.

CD71+VISTA+ erythroid cells promote the development and function of regulatory T cells through TGF-β

Cell-surface transferrin receptor (CD71⁺) erythroid cells are abundant in newborns with immunomodulatory properties. Here, we show that neonatal CD71⁺ erythroid cells express significant levels of V-domain Immunoglobulin (Ig) Suppressor of T Cell Activation (VISTA) and, via constitutive production of transforming growth factor (TGF)- β, play a pivotal role in promotion of naïve CD4⁺ T cells into regulatory T cells (Tregs). Interestingly, we discovered that CD71⁺VISTA⁺ erythroid cells produce significantly higher levels of TGF-β compared to CD71⁺VISTA⁻ erythroid cells and CD71⁺ erythroid cells from the VISTA knock-out (KO) mice. As a result, CD71⁺VISTA⁺ erythroid cells—compared to CD71⁺VISTA⁻ and CD71⁺ erythroid cells from the VISTA KO mice—significantly exceed promotion of naïve CD4⁺ T cells into induced Tregs (iTreg) via TGF-β in vitro. However, depletion of CD71⁺ erythroid cells had no significant effects on the frequency of Tregs in vivo. Surprisingly, we observed that the remaining and/or newly generated CD71⁺ erythroid cells following anti-CD71 antibody administration exhibit a different gene expression profile, evidenced by the up-regulation of VISTA, TGF-β1, TGF-β2, and program death ligand-1 (PDL-1), which may account as a compensatory mechanism for the maintenance of Treg population. We also observed that iTreg development by CD71⁺ erythroid cells is mediated through the inhibition of key signaling molecules phosphorylated protein kinase B (phospho-Akt) and phosphorylated mechanistic target of rapamycin (phospho-mTOR). Finally, we found that elimination of Tregs using forkhead box P3 (FOXP3)-diptheria toxin receptor (DTR) mice resulted in a significant expansion in the frequency of CD71⁺ erythroid cells in vivo. Collectively, these studies provide a novel, to our knowledge, insight into the cross-talk between CD71⁺ erythroid cells and Tregs in newborns. Our results highlight the biological role of CD71⁺ erythroid cells in the neonatal period and possibly beyond.

The primary role of the red blood cells is to transport oxygen, but we know relatively little about the other functions they perform. Following maturation, red blood cells exit the bone marrow and enter blood circulation. Their immature counterparts are normally absent or in very low frequency in the blood of healthy adults. However, we showed previously that immature red blood cells are abundant in the spleens of neonatal mice and in human umbilical cord blood and that these cells possess immunological properties. In this report, we studied a subset of neonatal immature red blood cells that express a protein called V-domain Immunoglobulin (Ig) Suppressor of T Cell Activation (VISTA) on their surface. We found that the presence of VISTA enables the cells to repeatedly produce the regulatory cytokine TGF-β. TGF-β induces a subset of naïve lymphocytes—the CD4⁺ T cells—and converts them into regulatory T cells, also known as Tregs. Tregs modulate and suppress other immune cells. Our studies provide novel insights, to our knowledge, into the immunological role of immature red blood cells in newborns.

Mode of delivery by an ulcerative colitis mother in a case of twins: Immunological differences in cord blood and placenta

AIM

To understand the effects of delivery mode on the immune cells frequency and function in cord blood and placenta.

METHODS

We evaluated immunological differences in cord blood and placental tissues for a case of twins one of which delivered vaginally while the other delivered by caesarian section (C-section). Cord blood mononuclear cells were isolated and placenta tissues were processed for cell isolation. Immune phenotyping was performed by flow cytometry methods following staining for T cells, natural killer (NK) cells, monocytes, neutrophils and CD71⁺ erythroid cells in both cord blood and placenta tissues. In addition, fetal calprotectin of twins was measured 12 wk after birth.

RESULTS

We found lower percentages of immune cells (e.g. T cells, monocytes and neutrophils) in the cord blood of C-section delivered compared to vaginally delivered newborn. In contrast, percentages of monocytes and neutrophils were > 2 folds higher in the placental tissues of C-section delivered newborn. More importantly, we observed lower percentages of CD71⁺ erythroid cells in both cord blood and placental tissues of C-section delivered case. Lower CD71⁺ erythroid cells were associated with a more pro-inflammatory milieu at the fetomaternal interface reflected by higher expression of inhibitory receptors on CD4⁺ T cells, higher frequency of monocytes and neutrophils. Furthermore, type of delivery impacted the gene expression profile in CD71⁺ erythroid cells. Finally, we found that C-section delivered child had > 20-fold higher FCP in his fecal sample at 12 wk of age.

CONCLUSION

Mode of delivery impacted immune cells profile in cord blood/placenta. In particular frequency of immunosuppressive CD71⁺ erythroid cells was reduced in C-section delivered newborn.

Anti-H can trigger apoptosis and down-regulate FUT1 expression in erythroid differentiated K562 cells without complement mediation

The reason why delayed RBC engraftment and pure red cell aplasia (PRCA) develop only in some but not all recipients of major ABO-incompatible hematopoietic stem cell transplantation (HSCT) remains elusive and the underlying mechanisms are not fully understood. Understanding how incompatible erythroid blood group antibodies (Abs) interact with ABH antigens (Ags) of grafts, and investigating how to induce artificially accommodation of grafts are of obvious importance in transplantation immunology. The effects of anti-H on proliferation, apoptosis, and α-(1,2)-fucosyltransferase gene (FUT1) expression in erythroid differentiated K562 cells were analyzed by the MTT assay, Annexin V/PI staining, and quantitative RT-PCR method. The growth of erythroid differentiated K562 cells was significantly suppressed when anti-H dilution was ≤ 1:8 (P<0.001, as compared with 1:16). Under the complement-free culture conditions, the apoptotic ratio of erythroid differentiated K562 cells was significantly increased when anti-H dilution was ≤ 1:16 (P<0.05, as compared with 1:32). The apoptosis was not only closely associated with anti-H dilution (F=138.991, P<0.001), but also correlated with treated time (F=583.249, P<0.001), which indicated typical dose- and time-dependent effects. Under the complement-free culture conditions, the FUT1 mRNA expression level was also suppressed when anti-H dilution was ≤ 1:16 (P<0.05, as compared with 1:32), which also manifested in typical dose-dependent (F=130.356, P<0.001) and time-dependent (F=1432.00, P<0.001) effects. The results confirm that anti-H can trigger apoptosis and down-regulate FUT1 expression in erythroid differentiated K562 cells without complement mediation. The findings suggest that anti-H could accommodate grafts through triggering apoptosis and down-regulating Fut1 expression to reduce ABH antigens.

[Preliminary study of autoantigens on the membrane of erythropoietic cells of the patients with BMMNC-Coomb's test(+) hemocytopenia]

OBJECTIVE

To observe the relationship between erythropoietin receptor (EPOR) and autoantibodies-IgG/IgM (auto-Ab) on the membrane of erythropoietic cells of the patients with bone marrow mononuclear cells (BMMNC)-Coomb's test(+) hemocytopenia (immunorelated pancytopenia (IRP)) and explore the probable autoantigens of auto-Ab in IRP.

METHODS

A total of 46 newly diagnosed IRP patients (15 with auto-Ab on erythropoietic cells and 31 without) and 18 healthy controls were enrolled. The EPOR expressions on their nuclear erythrocytes were tested with flow cytometry (FCM) to observe the relationship between EPOR and auto-Ab. EPOR mRNA was detected by reverse transcription (RT)-PCR. Stat5 and P-Stat5 proteins in nucleated erythrocytes were measured by Western blot. EPOR expressions on nucleated erythrocytes membrane were re-tested after stripping autoantibodies with glycine buffer.

RESULTS

(1) EPOR of auto-Ab(+) group (1.6% ± 0.9%)was significantly lower than that of auto-Ab(-) group (4.6% ± 4.1%, P < 0.01)and the latter was significantly higher than that of normal controls (2.3% ± 1.8%, P < 0.05). EPOR of IRP patients was inversely correlated with their auto-Ab (r = -0.543, P = 0.000). (2) EPOR mRNA of auto-Ab(+) group (0.68 ± 0.14)was significantly higher than that of auto-Ab(-) group (0.55 ± 0.12, P < 0.01) and normal controls (0.58 ± 0.12, P < 0.05). (3) Protein Stat5 of auto-Ab(+) group (1.45 ± 0.94) was significantly higher than that of normal controls (0.54 ± 0.36, P < 0.05). While P-Stat5 of auto-Ab(+) group (0.42 ± 0.18)was significantly lower than that of normal controls (0.85 ± 0.38, P < 0.05). (4) EPOR expression increased significantly after auto-Ab stripping.

CONCLUSIONS

The auto-Ab of some IRP patients blocks or competitively inhibits EPOR on the membrane of erythropoietic cells. And EPOR may be one of autoantigens in IRP.

Stem cell transplantation demonstrates that Sox6 represses εy globin expression in definitive erythropoiesis of adult mice

Sox6, a member of the Sox transcription factor family, is essential for the silencing of epsilon y globin gene expression in definitive erythropoiesis of mice. Homozygous Sox6-null mice are neonatally lethal, precluding analysis at later stages. We created adult mice that are deficient in Sox6 specifically in hematopoietic tissues by transplanting embryonic liver stem cells from Sox6-deficient mice into lethally irradiated congenic wild-type adult mice. The mice receiving mutant stem cells (mutant engrafted) showed high expression levels of epsilon y in bone marrow, spleen, and circulating blood compared with mice receiving wild-type and heterozygous stem cells (control engrafted). The level of expression of epsilon y in circulating blood was directly correlated with the percentage of successful mutant donor cell engraftment. Additionally, the mutant engrafted adult mice showed an increase in erythroid precursor cells in bone marrow, spleen, and blood. Thus, Sox6 continues to function as a major regulator of epsilon y in adult definitive erythropoiesis and is required for normal erythrocyte maturation. Therefore, Sox6 may provide a novel therapeutic target by reactivating epsilon y in patients with hemoglobinopathies such as sickle cell anemia and beta-thalassemia.

SIMULTANEOUS MEASUREMENT OF NUCLEATED CELL COUNTS AND CELLULAR DIFFERENTIALS IN RAT BONE MARROW EXAMINATION USING FLOW CYTOMETER

The purpose of this study was to establish the simultaneous measurement of nucleated cell counts and cellular differentials in rat bone marrow examination. The bone marrow cells were stained with an anthraquinone fluorescent DNA stain (DRAQ5) and fluorescence-labeled antibodies, and were analyzed quantitatively using a flow cytometer in the presence of internal standard beads. DRAQ5 distinguished populations of nucleated cells. The absolute counts of nucleated cells were determined using an internal standard, and were equivalent to that measured by the electrical resistance method. The population of nucleated cells was classified into myeloids and erythroids by labeling with CD11b/c and CD71 antibodies, respectively. In a separate examination, T- and B-lymphocytes were also classified by labeling with CD3 and CD45RA antibodies, respectively. The classification of each cell lineage was identical with that of the alternative flow-cytometric method in which cells were differentiated according to cellular size and the fluorescence of a peroxidase indicator, 2',7'-dichlorofluorescin. The ratios of cell lineage, together with myeloid/erythroid ratio (ME), were the same as those obtained by a manual microscopic method. The present flow cytometric method enables the simultaneous measurement of the total nucleated cell counts and cellular differentials of rat bone marrow cells, allowing for rapid and highly quantitative bone marrow examination in rats.

A small-scale serum-free liquid cell culture model of erythropoiesis to assess the effects of exogenous factors

Anaemia is an important global health problem. Therefore, it is crucial to understand its pathophysiology in various genetic or infectious diseases where dyserythropoiesis is a key pathological feature. To this effect, reproducible and reliable models of erythropoiesis in vitro are much needed as investigative tools. We have developed a serum-free liquid culture model of erythropoiesis using human umbilical cord blood CD34(+) cells cultured in the cytokine combination, interleukin-3 (IL-3), IL-6, stem cell factor (SCF) and erythropoietin (Epo), over 14 days. We found that these culture conditions favored erythroid differentiation over the expansion of the more primitive erythroid precursors. With an initiating culture density of 5x10(4) cells per ml, the nucleated cell fold expansion increased from 7.9+/-3.9 (range 4.5 to 11.1) after 4 days to 2990.2+/-1936.1 (range 626.6 to 6912.0) after 14 days in culture. Day-14 burst-forming unit-erythroid (BFU-E) frequencies peaked at day 4 (24.0+/-8.9%), with a marked decrease in BFU-E burst size as the cultures progressed. Time-course immunophenotypical profiles were characteristically erythroid with a decrease in CD34 expression (from 96.8+/-3.0% at day 0 to 0.8+/-0.8% at day 14), and a concomitant increase in the expression of erythroid-specific markers, CD36, glycophorin A (GpA) and CD71 (from 14.8+/-5.0%, 1.7+/-1.0% and 37.9+/-18.0% to 93.0+/-7.0%, 82.1+/-14.0% and 95.7+/-3.0%, respectively). Morphological studies revealed the presence of normoblasts with the complete absence of reticulocytes and mature erythrocytes after 14 days in culture. Once the culture conditions were optimized, we scaled down our culture model from 24-well plate (large-scale) to 96-well plate cultures (small-scale). We found that the small-scale cultures compared favorably with their large-scale counterpart in terms of erythroid progenitor cell proliferation and differentiation, particularly at low CD34(+) initiating cell doses. By using tumor necrosis factor-alpha (TNF-alpha), a known inhibitor of erythropoiesis, we validated our model system and showed a dose-dependent inhibition of erythroid differentiation with TNF-alpha in our cultures. Therefore, our results demonstrate a small-scale serum-free liquid culture model of erythropoiesis that is comparable with and complements our well-defined large-scale model. Our system would prove useful for screening the effects of exogenous factors on erythropoiesis in vitro.

Chromatin-binding in vivo of the erythroid kruppel-like factor, EKLF, in the murine globin loci

EKLF is an erythroid-specific, zinc finger-containing transcription factor essential for the activation of the mammalian beta globin gene in erythroid cells of definitive lineage. We have prepared a polyclonal anti-mouse EKLF antibody suitable for Western blotting and immunoprecipitation (IP) qualities, and used it to define the expression patterns of the EKLF protein during mouse erythroid development. We have also used this antibody for the chromatin-immunoprecipitation (ChIP) assay. EKLF was found to bind in vivo at both the mouse beta-major-globin promoter and the HS2 site of beta-LCR in the mouse erythroleukemia cells (MEL) in a DMSO-inducible manner. The DMSO-induced bindings of EKLF as well as three other proteins, namely, RNA polymerase II, acetylated histone H3, and methylated histone H3, were not abolished but significantly lowered in CB3, a MEL-derived cell line with null-expression of p45/NF-E2, an erythroid-enriched factor needed for activation of the mammalian globin loci. Interestingly, binding of EKLF in vivo was also detected in the mouse alpha-like globin locus, at the adult alpha globin promoter and its far upstream regulatory element alpha-MRE (HS26). This study provides direct evidence for EKLF-binding in vivo at the major regulatory elements of the mouse beta-like globin gene clusters the data also have interesting implications with respect to the role of EKLF-chromatin interaction in mammalian globin gene regulation.

Immunophenotypic differentiation patterns of normal hematopoiesis in human bone marrow: reference patterns for age-related changes and disease-induced shifts

BACKGROUND

The abundance of monoclonal antibodies (mAb) and the routine use of quadruple stainings in flow cytometry allow stepwise analysis of bone marrow (BM) samples that are suspected for abnormal hematopoiesis. A screening phase that precedes lineage-specific classification phases should be sufficient to assess whether the BM has a normal or abnormal composition, as well as to identify the abnormal differentiation lineage.

METHODS

For a quick and easy flow cytometric screening of BM samples, we selected six quadruple immunostainings that cover multiple differentiation stages of the B-cell, monocytic, granulocytic, and erythroid lineages: TdT/CD20/CD19/CD10 and CD45/CD34/CD19/CD22 for B cells, CD34/CD117/CD45/CD13.33 for precursor granulocytic and precursor monocytic cells (myelo/monoblasts), CD14/CD33/CD45/CD34 for monocytic cells, CD16/CD13/CD45/CD11b for granulocytic cells, and CD71/CD235a/CD45/CD117 for erythroid cells.

RESULTS

The six quadruple immunostainings reveal specific staining patterns in normal BM, which allow the recognition of various subpopulations of the respective lineages. These staining patterns can be used as a frame of reference for recognition of normal and abnormal BM development. Examples of normal (age-related) variations in these otherwise stable staining patterns are presented together with several abnormal differentiation patterns.

CONCLUSIONS

Although alternative immunostainings can be used (e.g., including NK- and T-cell markers), we feel that the selected six stainings represent a comprehensive and easy screening phase for quick identification of shifts in the composition of the studied differentiation lineages, reflecting age-related changes or disease-induced BM abnormalities.

Ku80 autoantigen as a cellular coreceptor for human parvovirus B19 infection

Human parvovirus B19 (B19) infects human erythroid cells expressing P antigen. However, some cell lines that were positive for P antigen failed to bind B19, whereas some cell lines had an ability to bind B19 despite undetectable expression of P antigen. We here demonstrate that B19 specifically binds with Ku80 autoantigen on the cell surface. Furthermore, transfection of HeLa cells with the gene of Ku80 enabled the binding of B19 and allowed its entry into cells. Moreover, reduction of cell-surface expression of Ku80 in KU812Ep6 cells, which was a high-sensitive cell line for B19 infection, by short interfering RNA for Ku80 resulted in the marked inhibition of B19 binding in KU812Ep6 cells. Although Ku80 originally has been described as a nuclear protein, human bone marrow erythroid cells with glycophorin A or CD36, B cells with CD20, or T cells with CD3 were all positive for cell-surface expression of Ku80. B19 infection of KU812Ep6 cells and bone marrow cells was inhibited in the presence of anti-Ku80 antibody. Our data suggest that Ku80 functions as a novel coreceptor for B19 infection, and this finding may provide an explanation for the pathologic immunity associated with B19 infection.

[Expansion of erythroid progenitors and CD34+ cells by umbilical cord blood mononuclear cells]

Cord blood represents a large source of hematopoietic stem/progenitor cells. It can be induced to proliferate directly into erythroid progenitors in a appropriate ex vivo culture condition, then to generate mature red blood cells after injection into the body. The combination of Flt3 ligand, TPO, SCF and EPO is ideal for cord blood MNC to proliferate into erythroid progenitors. This study was aimed to evaluate the effect of FL, SCF and TPO on CD34(+) expansion. and to investigate influence of the cytokine combination on the proliferation of the CD34(+) cells. Mononuclear cells (MNC) were cultured in serum-free liquid culture system. Experiments were divided into 3 groups. In the group A as control no cytokines were added in the culture system; in the group B the cells cultured with SCF + FL + TPO + EPO + IGF-1; in the group C the cells were cultured with SCF + FL + TPO. EPO and IGF-1 were added at day 6. Part of the renewed MNCs and colony-forming units were counted, the proportion of CD34(+), CD34(+) CD71(+), CD71(+) GPA(+) cells was detected by FACS. The result showed that after 10 days, the the total cord blood cells increased 6.89-folds in group B and 3.06-folds in group C (P < 0.05). The CD34(+) cells increased 4.83-folds in group B and 2.47-folds in group C (P < 0.05). The colony-forming cells (CFCs) increased 4.3-folds in group B and 2.5-folds in group C (P < 0.05). Erythroid progenitors (BFU-E) and CFU-E increased 5.4-folds in group B and 3.1-folds in group C (P < 0.05). The CD34(+)CD71(+) cells increased 8.72-folds in group B and 3.37-folds in group C (P < 0.05). The CD71(+) GPA(+) cells increased 53.4-folds in group B and 30.29-folds in group C. They were different at any time point (P < 0.05). It is concluded that in the group with FL + SCF + TPO, CD34(+) cells and CFC can greatly be expanded from cord blood MNC in the serum-free culture system. In the group with FL + SCF + TPO + EPO + IGF-1, erythroid progenitors can greatly be expanded in the serum-free culture system, supplying EPO at day 0 was better than supplying at day 6. Since the largest number of colony-forming cells such as BFU-E and CFU-E were gained in the TPO + SCF + FL + EPO + IGF-1 group at day 10, the harvest time after cultivation in vitro should be selected at day 10.

Erythroid cells in immunoregulation: characterization of a novel suppressor factor

Nucleated erythroid cells (EC) have been previously reported to possess a potent natural suppressor (NS) activity for B-cell responses. In this study, we demonstrate that murine EC are able to reduce not only lipopolysaccharide (LPS)-driven B-cell proliferation, but also proliferative and cytotoxic T-cell responses generated in a primary allogeneic mixed lymphocyte culture (MLC); and that a soluble low molecular weight factor may be involved in such EC-derived immunoregulation. In addition, the erythroid cell-derived suppressor factor (ESF) was found to be capable of effectively reducing the allergen-driven proliferation of peripheral blood mononuclear cells (PBMC) isolated from allergic patients. From the data presented herein, it appears that ESF is heat-stable (80 degrees C for 20 min) and has molecular weight (MW) lower or close to 0.5 kDa. ESF activity is resistant to both enzyme (trypsin plus chymotrypsin) proteolysis and action of the enzymes such as lipase and phospholipase C. On the other hand, ESF is effectively inactivated by neuraminidase treatment, suggesting the presence in its structure of sialic residue(s). The neuraminidase-sensitive, ESF-like activity is readily detected in the medium conditioned with normal mouse bone marrow (BM) cells. On fractionation of low MW erythroid products on a reversed-phase C16 column in a linear acetonitrile gradient (5-95%), ESF activity is detected in the first peak alone with the shortest time of its retention by the column. The results suggest that (1) by producing ESF, EC may regulate both B- and T-cell-mediated immune processes and (2) based on its physicochemical and biological characteristics, ESF can be distinguished from each of earlier characterised suppressor mediators of bone marrow origin.