Macrophages form erythropoietic niches and regulate iron homeostasis to adapt erythropoiesis in response to infections and inflammation

It has recently emerged that tissue-resident macrophages are key regulators of several stem cell niches orchestrating tissue formation during development, as well as postnatally, when they also organize the repair and regeneration of many tissues including the hemopoietic tissue. The fact that macrophages are also master regulators and effectors of innate immunity and inflammation allows them to coordinate hematopoietic response to infections, injuries, and inflammation. After recently reviewing the roles of phagocytes and macrophages in regulating normal and pathologic hematopoietic stem cell niches, we now focus on the key roles of macrophages in regulating erythropoiesis and iron homeostasis. We review herein the recent advances in understanding how macrophages at the center of erythroblastic islands form an erythropoietic niche that controls the terminal differentiation and maturation of erythroblasts into reticulocytes; how red pulp macrophages in the spleen control iron recycling and homeostasis; how these macrophages coordinate emergency erythropoiesis in response to blood loss, infections, and inflammation; and how persistent infections or inflammation can lead to anemia of inflammation via macrophages. Finally, we discuss the technical challenges associated with the molecular characterization of erythroid island macrophages and red pulp macrophages.

PPARγ is essential for the development of bone marrow erythroblastic island macrophages and splenic red pulp macrophages

Tissue-resident macrophages play a crucial role in maintaining homeostasis. Macrophage progenitors migrate to tissues perinatally, where environmental cues shape their identity and unique functions. Here, we show that the absence of PPARγ affects neonatal development and VCAM-1 expression of splenic iron-recycling red pulp macrophages (RPMs) and bone marrow erythroblastic island macrophages (EIMs). Transcriptome analysis of the few remaining Pparg-deficient RPM-like and EIM-like cells suggests that PPARγ is required for RPM and EIM identity, cell cycling, migration, and localization, but not function in mature RPMs. Notably, Spi-C, another transcription factor implicated in RPM development, was not essential for neonatal expansion of RPMs, even though the transcriptome of Spic-deficient RPMs was strongly affected and indicated a loss of identity. Similarities shared by Pparg- and Spic-deficient RPM-like cells allowed us to identify pathways that rely on both factors. PPARγ and Spi-C collaborate in inducing transcriptional changes, including VCAM-1 and integrin αD expression, which could be required for progenitor retention in the tissue, allowing access to niche-related signals that finalize differentiation.

Rainbow Trout Red Blood Cells Exposed to Viral Hemorrhagic Septicemia Virus Up-Regulate Antigen-Processing Mechanisms and MHC I&II, CD86, and CD83 Antigen-presenting Cell Markers

Nucleated teleost red blood cells (RBCs) are known to express molecules from the major histocompatibility complex and peptide-generating processes such as autophagy and proteasomes, but the role of RBCs in antigen presentation of viruses have not been studied yet. In this study, RBCs exposed ex vivo to viral hemorrhagic septicemia virus (VHSV) were evaluated by means of transcriptomic and proteomic approaches. Genes and proteins related to antigen presentation molecules, proteasome degradation, and autophagy were up-regulated. VHSV induced accumulation of ubiquitinated proteins in ex vivo VHSV-exposed RBCs and showed at the same time a decrease of proteasome activity. Furthermore, induction of autophagy was detected by evaluating LC3 protein levels. Sequestosome-1/p62 underwent degradation early after VHSV exposure, and it may be a link between ubiquitination and autophagy activation. Inhibition of autophagosome degradation with niclosamide resulted in intracellular detection of N protein of VHSV (NVHSV) and p62 accumulation. In addition, antigen presentation cell markers, such as major histocompatibility complex (MHC) class I & II, CD83, and CD86, increased at the transcriptional and translational level in rainbow trout RBCs exposed to VHSV. In summary, we show that nucleated rainbow trout RBCs can degrade VHSV while displaying an antigen-presenting cell (APC)-like profile.

Thrombocytopenia and Anemia with Anti-c-Mpl antibodies Effectively Treated with Cyclosporine in a Patient with Rheumatoid Arthritis and Chronic Renal Failure

A 61-year-old woman with rheumatoid arthritis who was undergoing hemodialysis for end-stage renal failure was transferred to our hospital due to severe thrombocytopenia and anemia. A bone marrow biopsy showed the complete absence of megakaryocytes and erythroblasts. Cyclosporine treatment resulted in the improvement of her megakaryocyte and erythroblast levels, and a decrease in her serum level of anti-c-Mpl (thrombopoietin receptor) antibodies. After this initial improvement, her anemia progressively worsened, despite the continuous administration of immunosuppressive therapy with cyclosporine. Her platelet and leukocyte counts remained stable. This is the first report of a probable case of anti-c-Mpl antibody-associated pure red cell aplasia and acquired amegakaryocytic thrombocytopenic purpura.

Erythropoietin Receptors and IgG Autoantibody Expression on Nucleated Erythrocytes in Some Cases of Immuno-Related Pancytopenia

BACKGROUND

In recent years, we have detected autoantibodies in bone marrow (BM) hemopoietic cells in some patients with idiopathic cytopenia of undetermined significance (ICUS), termed immunorelated pancytopenia (IRP). However, we know little about the targets of these autoantibodies.

METHODS

Twenty-six newly diagnosed IRP patients with IgG autoantibody on nucleated erythrocytes and 20 healthy donors as controls were enrolled in this study. The serum erythropoietin (EPO) level was examined by ELISA. Expression of EPO receptor (EPOR) and IgG autoantibody on the membrane of nucleated erythrocytes were detected by flow cytometry before and after autoantibody stripping.

RESULTS

The serum EPO level of the untreated patients was 199.9 ± 106.4 mIU/mL, which was significantly higher than that of normal controls (13.2 ± 8.41 mIU/mL, p < 0.01). EPOR expression on nucleated erythrocytes in the patients was 1.38 ± 0.73%, lower than that of normal controls (2.33 ± 1.73%), but there was no significant difference; EPOR in these patients was inversely correlated with IgG autoantibody on erythrocytes (r = -0.479, p = 0.013). The regression equation was Y = 0.116-0.479X; EPOR expression on the membrane increased significiantly (5.63 ± 4.99%, p < 0.01) after stripping the autoantibodies. After immunosuppressive treatment, median hemoglobin increased from 72 g/L to 98 g/L, and median reticulocytes increased from 1.46% to 3.56%.

CONCLUSIONS

IgG autoantibodies might block or competitively inhibit EPOR on nucleated erythrocytes in some cases of ICUS.

Erythroblastic islands in the bone marrow of patients with immune-related pancytopenia

BACKGROUND

Immune-related pancytopenia (IRP) is characterized by pancytopenia caused by autoantibody-mediated bone marrow destruction or suppression. The bone marrows of IRP patients have remarkably increased erythroblastic islands (EIs).

METHODOLOGY AND PRINCIPAL FINDINGS

We determined the immunoglobulin G (IgG) autoantibodies in some parts of EIs of IRP patients using immunofluorescence to investigate the biological function of EIs with IgG in the pathophysiology of IRP. The dominant class of autoantibodies detected in mononuclear cells was IgG (CD34 IgG, CD15 IgG, and GlycoA IgG), specifically IgG on GlycoA-positive cells (GlycoA IgG). Results show that extravascular hemolysis occurred in IRP through IgG autoantibodies in the EIs. These data included a high percentage of reticulocytes in the peripheral blood, hypererythrocytosis in the bone marrow, and high serum bilirubin. Furthermore, we examined the macrophages in the bone marrow of IRP patients. The results show that the number of activated macrophages relatively increased, and the phagocytic activity of macrophages significantly increased.

CONCLUSIONS AND SIGNIFICANCE

Increased EIs with IgG were the sites of erythroblast phagocytosis by the activated macrophages, rather than erythropoietic niches. The IgG autoantibodies in the EIs possibly functioned as adhesion molecules for a ring of erythroblasts around the macrophages, thereby forming morphologic EIs.

RNA-Seq reveals an integrated immune response in nucleated erythrocytes

Background

Throughout the primary literature and within textbooks, the erythrocyte has been tacitly accepted to have maintained a unique physiological role; namely gas transport and exchange. In non-mammalian vertebrates, nucleated erythrocytes are present in circulation throughout the life cycle and a fragmented series of observations in mammals support a potential role in non-respiratory biological processes. We hypothesised that nucleated erythrocytes could actively participate via ligand-induced transcriptional re-programming in the immune response.

Methodology/Principal Findings

Nucleated erythrocytes from both fish and birds express and regulate specific pattern recognition receptor (PRR) mRNAs and, thus, are capable of specific pathogen associated molecular pattern (PAMP) detection that is central to the innate immune response. In vitro challenge with diverse PAMPs led to de novo specific mRNA synthesis of both receptors and response factors including interferon-alpha (IFNα) that exhibit a stimulus-specific polysomal shift supporting active translation. RNA-Seq analysis of the PAMP (Poly (I∶C), polyinosinic∶polycytidylic acid)-erythrocyte response uncovered diverse cohorts of differentially expressed mRNA transcripts related to multiple physiological systems including the endocrine, reproductive and immune. Moreover, erythrocyte-derived conditioned mediums induced a type-1 interferon response in macrophages thus supporting an integrative role for the erythrocytes in the immune response.

Conclusions/Significance

We demonstrate that nucleated erythrocytes in non-mammalian vertebrates spanning significant phylogenetic distance participate in the immune response. RNA-Seq studies highlight a mRNA repertoire that suggests a previously unrecognized integrative role for the erythrocytes in other physiological systems.

[Expression of differentiation antigens on bone marrow myeloid cells of the patients with myelodysplastic syndromes and its clinical significances]

OBJECTIVE

To detect the abnormal differentiation of bone marrow myeloid cells in myelodysplastic syndromes (MDS) and its correlation with the prognosis of MDS patients.

METHODS

Quantitative assessment of CD11b, CD13, CD16 and HLA-DR expression on the membrane of bone marrow granulocytes, and CD71 and glycophorin A on erythroblasts of 12 MDS patients in low-risk, 22 in high-risk and 31 normal controls was conducted with flow cytometry. The correlation between the abnormality and the prognosis of MDS cases were analyzed.

RESULTS

The granulocytic differentiation was analyzed with the combinations of CD13/CD11b, CD13/CD16 and CD11b/CD16. The "right hook", "sickle" and "retroflex 7" shape expressions were found in normal controls while there were various changes in MDS groups. The ratios of CD11b-/CD11b+ (0.39 +/- 0.34) and CD16-/CD16+ (1.33 +/- 0.77) were significantly higher in high-risk MDS group than those of control group (0.07 +/- 0.05 and 0.39 +/- 0.31 respectively) (P < 0.05). The MFI (mean fluorescence index) of SSC (side scatter) in the granulocyte gate of MDS groups was lower while MFI of CD13 was higher. The mean percentages of CD11b-HLA-DR+ 3.88% +/- 3.07%, CD11b-HLA-DR- 16.23% +/- 15.59%, CD16-HLA-DR- 41.12% +/- 24.53%, CD11b+CD16- 33.53% +/- 17.26% and CD13+CD16- 44.51% +/- 21.99% granulocytes of high-risk MDS group were significantly higher than those of low-risk and control groups (P < 0.05). The erythroid cell lineage differentiation was analyzed with CD71/glycophorin A combination. Double positive expression was found in all controls, but asynchronous expression of CD71/glycophorin A was found in some MDS cases. The mean percentage of double positive cells in CD45- and glycophorin A+ cell population was significantly lower in low-risk and high-risk MDS groups. The abnormal numbers and patterns of the antigen expression of MDS cases per case correlated directly with their IPSS (international prognostic scoring system) (r = 0.690, P = 0.000) and WPSS (WHO adapted prognostic scoring system) (r = 0.651, P = 0.000) scores.

CONCLUSION

There is an abnormal expression of differentiation antigens on bone marrow myeloid cells of MDS patients. And the severity is correlated with the prognosis. The abnormal differentiation of myeloid cells is probably involved in the pathogenesis of MDS. So the examination of these antigenic expressions with flow cytometry might be helpful for diagnosis and prognosis of MDS.

Bone marrow mitogen-stimulated direct antiglobulin test in a case of erythroblastic synartesis

In this article we report a case of erythroblastic synartesis, a rare disease characterized by ineffective erythropoiesis, clusters of erythroblasts due to membrane invaginations, in which an autoimmune pathogenesis is hypothesized. We investigated the presence of anti-erythroblast autoimmunity in bone marrow cultures using a mitogen-stimulated direct antiglobulin test, a method reported to be able to disclose a latent autoimmunity in various diseases. The test revealed the presence of erythroblast-bound IgG, supporting the hypothesis of the autoimmune pathogenesis of erythroblastic synartesis. Supernatants induced the same specific morphological features, i.e erythroblastic clustering and diserythropoietic signs (multiple nuclei, nuclear inclusions, and intercellular bridges) in normal progenitors.

[The role of bone marrow cells immunophenotypic study by flow cytometry in diagnosing myelodysplastic syndrome]

Myelodysplastic syndromes are a heterogeneous group of clonal bone marrow disorders characterized by dysplasia, progressive bone marrow failure, and increased risk of transformation to acute myeloid leukemia. Although diagnostic criteria are well established, a diagnosis based on morphologic and cytogenetic findings is often difficult in a significant number of patients. Multiparametric flow cytometric immunophenotyping is a highly sensitive and specific method for quantitative and qualitative evaluation of hematopoietic cells. Flow cytometry is used to identify dysregulated antigen expression of myeloid cells, estimate the proportion of bone marrow blasts cells, and reveal their abnormal immunophenotype. Recent data suggest that flow cytometry adds important prognostic information to the widely accepted International Prognostic Scoring System.

Tissue-specific histone modification and transcription factor binding in α globin gene expression

To address the mechanism by which the human globin genes are activated during erythropoiesis, we have used a tiled microarray to analyze the pattern of transcription factor binding and associated histone modifications across the telomeric region of human chromosome 16 in primary erythroid and nonerythroid cells. This 220-kb region includes the α globin genes and 9 widely expressed genes flanking the α globin locus. This un-biased, comprehensive analysis of transcription factor binding and histone modifications (acetylation and methylation) described here not only identified all known cis-acting regulatory elements in the human α globin cluster but also demonstrated that there are no additional erythroid-specific regulatory elements in the 220-kb region tested. In addition, the pattern of histone modification distinguished promoter elements from potential enhancer elements across this region. Finally, comparison of the human and mouse orthologous regions in a unique mouse model, with both regions coexpressed in the same animal, showed significant differences that may explain how these 2 clusters are regulated differently in vivo.

Multiple Members of the TNF Superfamily Contribute to IFN-γ-Mediated Inhibition of Erythropoiesis

IFN-gamma inhibits the growth and differentiation of erythroid precursor cells and mediates hemopoietic suppression through mechanisms that are not completely understood. We found that treatment of human erythroid precursor cells with IFN-gamma up-regulates the expression of multiple members of the TNF family, including TRAIL and the recently characterized protein TWEAK. TWEAK and its receptor fibroblast growth factor-inducible 14 (Fn14) were expressed by purified erythroblasts at all the stages of maturation. Exposure to recombinant TWEAK or agonist anti-Fn14 Abs was able to inhibit erythroid cell growth and differentiation through caspase activation. Because other members of the TNF family such as TRAIL and CD95 ligand (CD95L) are known to interfere with erythroblast growth and differentiation, we investigated the role of different TNF/TNFR family proteins as potential effectors of IFN-gamma in the immature hemopoietic compartment. Treatment of erythroid precursor cells with agents that blocked either TRAIL, CD95L, or TWEAK activity was partially able to revert the effect of IFN-gamma on erythroid proliferation and differentiation. However, the simultaneous inhibition of TRAIL, TWEAK, and CD95L resulted in a complete abrogation of IFN-gamma inhibitory effects, indicating the requirement of different receptor-mediated signals in IFN-gamma-mediated hemopoietic suppression. These results establish a new role for TWEAK and its receptor in normal and IFN-gamma-mediated regulation of hematopoiesis and show that the effects of IFN-gamma on immature erythroid cells depend on multiple interactions between TNF family members and their receptors.

Fetal cells in maternal blood: a comparison of methods for cell isolation and identification

OBJECTIVE

A variety of methods have been used to select and identify fetal cells from maternal blood. In this study, a commonly used 3-step selection method is compared with selection directly from whole blood. Identification of fetal origin by XY FISH of male cells was also evaluated.

METHODS

Maternal blood was drawn either before invasive chorion villus sampling (pre-CVS) or after (post-CVS) from women carrying a male fetus. Fetal cells were isolated either by density gradient centrifugation succeeded by CD45/CD14 depletion and CD71-positive selection from CD45/CD14-negative cells, or by CD71-positive selection directly from whole blood. The true origin of fetal cells recovered by the two methods was established by two rounds of XY chromosome FISH in reverse colors, in some instances combined with anti-zeta (zeta) or anti-zeta/anti-gamma (gamma) antibody staining.

RESULTS

In blood samples taken post-CVS and enriched by CD71 selection directly from whole blood, fetal cells were identified with a frequency that was almost four orders of magnitude higher than in post-CVS samples enriched by the 3-step method. In blood samples taken pre-CVS and enriched by the 3-step procedure, no fetal cells were identified by reverse color FISH in 371 ml of blood. In similar samples enriched by CD71 selection on whole blood, two fetal cells were identified in 27 ml of blood. Rehybridization with X and Y chromosome probes with reverse colors was necessary to exclude false Y chromosome signals. Not all fetal cells identified by the presence of a true Y chromosome signal stained with anti-zeta antibody.

CONCLUSIONS

Selection of fetal NRBCs from maternal blood by CD71-positive selection directly from whole blood is superior to density gradient centrifugation succeeded by CD45/CD14 depletion and CD71 selection of CD45/CD14-negative cells. Combining two markers for fetal origin is recommended for unambiguously identifying a cell as fetal.

A monoclonal antibody with potential for aiding non-invasive prenatal diagnosis: utility in screening of pregnant women at risk of preeclampsia

The development of a non-invasive method of prenatal diagnosis in maternal blood has been the goal of our investigations during the last years. We have developed several anti-CD71 monoclonal antibodies and optimized a protocol for the isolation of nucleated red blood cells (NRBC) from peripheral maternal blood. The enhanced traffic of fetal erythroblasts into the maternal circulation in preeclampsia has been investigated by several groups. In this study, we compared one of our antibodies, 2F6.3, with a commercial anti-CD71 antibody in blood samples from pregnant women suffering pregnancy-induced hypertension (PIH) and in a control group of pregnant women without clinical features suggestive of an increased risk of developing preeclampsia. The mAb 2F6.3, developed by our group, has succeeded in isolating a significantly higher number of erythroblasts with less maternal cell contamination than the commercial antibody in both women with PIH and in the control group (p<0.01; Wilcoxon Signed Ranks Test). Fluorescence in situ hybridization analysis also demonstrated that 2F6.3 is a better antibody for the isolation of fetal NRBC in maternal blood than the commercial anti-CD71 antibody.

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.

Cold weather exercise and airway cytokine expression

Athletes who perform repeated exercise while breathing cold air have a high prevalence of asthmalike chronic airway disease, but the mechanism linking such activity to airway inflammation is unknown. We used a novel animal model (exercising horses) to test the hypothesis that exercise-induced chronic airway disease is caused by exposure of intrapulmonary airways to unconditioned air, resulting in the upregulation of cytokine expression. Bronchoalveolar lavage fluid (BALF) was obtained from eight horses 5 h after submaximal exercise while they breathed room temperature or subfreezing air in a random crossover design. BALF total and differential nucleated cell counts were determined, and relative cytokine mRNA expression in BALF nucleated cells was quantified by real-time RT-PCR using primer and probe sequences specific for equine targets. There were no significant changes in total or differential cell concentrations between BALF recovered after warm and cold air exercise, although there was a strong trend toward increased concentrations of airway epithelial cells after cold air exercise (P = 0.0625). T(H)2 cytokines IL-4, IL-5, and IL-10 were preferentially upregulated after cold air exercise 12-, 9-, and 10-fold, respectively, compared with warm air exercise. Other cytokines (IL-2 and IL-6) were upregulated to a lesser extent (6- and 3-fold, respectively) or not at all (IL-1, IL-8, IFN-gamma, and TNF-alpha). These results suggest that cold weather exercise can lead to asthmalike airway disease through the local induction of cytokines typical of the T(H)2 phenotype.

[Immunopathomorphology of the human placental barrier in the first trimester of pregnancy complicated by the inflammation of the birth-ways]

The effect of ascending infection of birth-ways on transport of maternal immunoglobulins (Igs) through the placental barrier in humans during the first trimester of pregnancy was studied. The transport of Igs is seen already in 3.5-to 5-week-old embryos, and different cellular and biochemical compounds participate at each stage of this process. Transport of Igs through the trophoblast is carried out due to the secretory component (SC) and, perhaps, to some other receptors. Monocytes together with Igs penetrate into capillaries between the endothelial cells and are transported with the blood all over the body. It seems that SC and other receptors help Igs to penetrate into capillaries through the endothelium. Further, Igs are transported with erythroblasts. In the development without infection the transport of IgG was seen in all cases studied. Inflammation of the birth-ways is accompanied by an increase in transport of all Igs, already in early embryogenesis. Three groups were distinguished: 1) abortions without inflammation; 2) cases with signs of moderate inflammation (endometritis, deciduitis); 3) cases with intensive inflammation with necrosis and leucocytic infiltration. Transport of Igs was seen in 77.8% cases of the first group and in all cases of groups 2 and 3. Transport of IgM was not found in the first group, but was seen in 50% cases of group 2 and 66.7% of group 3.

Production of hemo- and immunoregulatory cytokines by erythroblast antigen+ and glycophorin A+ cells from human bone marrow

BACKGROUND

Erythroid nuclear cells (ENC) of the bone marrow (BM) have not previously been considered as important producers of wide spectrum of haemo- and immunoregulatory cytokines. The aim of the current work was to confirm the production of the main hemo- and immunoregulatory cytokines in human ENC from BM.

RESULTS

We used native human BM ENC in our experiments. We for the first time have shown, that the unstimulated erythroblasts (Gl A+ or AG-EB+) produced a wide spectrum of immunoregulatory cytokines. Human BM ENC produce cytokines such as interleukin (IL)-1beta, IL-2, IL-4, IL-6, interferon (IFN)-gamma, transforming growth factor (TGF)-beta1, tumor necrosis factor (TNF)-alpha and IL-10. They can be sub-divided into glycophorin A positive (Gl A+) and erythroblast antigen positive (AG-EB+) cells. To study potential differences in cytokine expression between these subsets, ENC were isolated and purified using specific antibodies to Gl A and AG-EB and the separated cells were cultivated for 24 hours. The cytokine contents of the supernatant were measured by electrochemiluminescence immunoassay. Quantitative differences in TGF-beta1 and TNF-alpha production were found between Gl A+ and AG-EB+ BM ENC. Furthermore, in vitro addition of erythropoietin (EPO) reduced IFN-gamma and IL-2 production specifically by the AG-EB+ ENC. Thus, Gl A+ and AG-EB+ ENC produce IL-1beta, IL-2, IL-4, IL-6, IFN-gamma, TGF-beta1 and TNF-alpha. Gl A+ ENC also produce IL-10.

CONCLUSION

Cytokine production by erythroid nuclear cells suggests that these cells might be involved in regulating the proliferation and differentiation of hematopoietic and immunocompetent cells in human BM.

[Use of specific antibody to detect fetal erythroblasts in maternal circulation]

OBJECTIVE

To investigate the feasibility of using immunohistochemical technique to detect the presence of fetal erythroblasts in the maternal circulation for prenatal diagnosis.

METHODS

Maternal blood was obtained from 30 pregnant women at 8 to 26 weeks of gestation. Nucleated red blood cells (NRBCs) were separated with Percoll using a discontinuous density gradient method, and then smeared on microscope slides using cytocentrifugation. Slides were stained with antibody against the gamma-chain of fetal hemoglobin (HbF). All positive NRBCs were collected by micromanipulator under microscopic observation, and then amplified by improved primer extension preamplification(PEP). Sex and Duchenne's musclar dystrophy (DMD) genetic diagnosis were determined from a small aliquot of the PEP reaction.

RESULTS

NRBCs stained with HbF were found in all of the blood from the 30 pregnant women at 8 to 26 weeks of gestation. 17 male fetuses and 13 female fetuses were detected in the 30 cases. These results coincided with those of induced labor or amniotic fluid control, and 8 fetuses at the risk of DMD were diagnosed.

CONCLUSION

This diagnostic method using immunohistochemical technique to mark fetal NRBC shows good application prospects.

Rare cell isolation using antibodies covalently linked to slides: application to fetal cells in maternal blood

We describe here a new type of method for isolation of rare cell populations in biological fluids. The method is based on the anthraquinone technology for covalent binding of molecules to a polymer surface. An anthraquinone molecule conjugated via a linker to an electrophilic group (AQ Immobilizer trade mark reagent, Exiqon A/S) is covalently bound to a polymer surface by UV irradiation. The electrophilic group of this AQ reagent can covalently bind a specific antibody directed against a specific cell marker. Applying a cell sample to the functional surface, the cells having the specific cell marker on the cell surface will bind to the antibody on the functional surface. Using this technique, even extremely small cell populations may be isolated. We succeeded in isolating fetal cells from maternal blood samples in the first trimester for chromosome defects genetic diagnosis.

Decreased expression of membrane alpha4beta1, alpha5beta1 integrins and transferrin receptor on erythroblasts in splenectomized patients with beta-thalassemia intermedia. Parallel assessment of serum soluble transferrin receptors levels

Dysfunction of cell membrane is a recognized consequence of the pathogenetic process underlying the beta-thalassemia syndromes and it is reasonable to hypothesize that surface structures crucial for the development of erythroid lineage may also be affected. The study included six adult splenectomized patients with beta-thalassemia intermedia. Expression of alpha4beta1 integrin (CD49d/CD29), alpha5beta1 integrin (CD49e/CD29) and transferrin receptor (CD71) on peripheral blood and bone marrow erythroblasts and on erythroid precursors grown in vitro was studied by flow cytometry and immunocytochemistry. Serum soluble transferrin receptor levels (sCD71) were also measured with enzyme-linked immunosorbent assay. In beta-thalassemic patients, significant reduction of CD49d, CD29 and CD71 expression was found in peripheral blood nucleated red cells, compared to patients presenting with erythroblasts in the circulation because of other diseases. Marrow erythroblasts were also deficient for the same molecules against the erythroblasts in iron deficiency anemia. All molecules tested were greatly diminished on erythroid precursors developed in vitro from the patients' cells. Serum sCD71 levels were much higher in thalassemic patients in comparison to both patients with iron deficiency anemia and healthy individuals. The loss of certain integrins and CD71 from erythroid precursors in beta-thalassemia intermedia could be attributed to a generalized membrane dysfunction, perhaps affecting the integrity of their transmembrane domains. The elevation of serum sCD71 levels may be the result of the increased red cell lineage turnover or, alternatively, may indicate increased shedding from the cells to prevent iron overload. In any case, further molecular study of the membrane components is warranted to provide a better understanding of the pathogenetic process in beta-thalassemia syndromes.

A new anti-hemoglobin F antibody against synthetic peptides for the detection of F-cell precursors (F-blasts) in bone marrow

To date there are few antibodies available for the detection of fetal hemoglobin (HbF)-containing erythroblasts (F-blasts) in paraffin-embedded hematopoietic tissues. Recently, we developed a new polyclonal antibody specific to F-blasts by immunization of a rabbit with synthetic peptides of human HbF. Specificity and reactivity of the antibody were confirmed by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry. ELISA confirmed that the antibody showed strong immunoreactivity to fetal hemoglobin but no reaction to adult hemoglobin. The antibody could detect the presence of fetal blood hemolysates (10 microg/mL) at a dilution of 10(-5). According to immunohistochemical analysis, there were strong positive reactions to fetal erythroblasts in the liver and the spleen at 29 weeks of gestation and to erythroblasts from patients with myelodysplastic syndromes and erythroleukemia but no reactions to normal adult erythroblasts in bone marrow. Fetal erythrocytes in fetal blood vessels of placental tissues were strictly distinguished from maternal erythrocytes in the same sections by their positive reactions, indicating the presence of HbF. This new antibody will be a useful tool for studying fetal hemoglobin synthesis and for detecting F-blasts in archival specimens of various hematological diseases.

The distribution of PIG-A gene abnormalities in paroxysmal nocturnal hemoglobinuria granulocytes and cultured erythroblasts

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hemolytic anemia that is characterized by a deficiency of glycosylphosphatidylinositol-anchored membrane proteins due to phosphatidylinositol glycan-class A (PIG-A) gene abnormalities in various lineages of peripheral blood cells and hematopoietic precursors. The purpose of our study was to clarify the distribution of PIG-A gene abnormalities among various cell lineages during differentiation and maturation in PNH patients. The expression of CD16b or CD59 in peripheral blood granulocytes or cultured erythroblasts from three Japanese PNH patients was analyzed using flow cytometry. PIG-A gene abnormalities in both cell types, including glycophorin A(+) bone marrow erythroblasts, were examined using nucleotide sequence analysis. The expression study of PIG-A genes from each patient was also performed using JY-5 cells.Flow cytometry revealed that the erythroblasts consisted of negative, intermediate, and positive populations in Cases 1 and 3 and negative and intermediate populations in Case 2. The granulocytes consisted of negative and positive populations in all three cases. DNA sequence analysis indicated that all the PNH cases had two or three types of PIG-A gene abnormalities, and that a predominant clone with an abnormal PIG-A gene was different in granulocytes and erythroblasts from Cases 2 and 3. Expression studies showed that all the mutations from the patients were responsible for the null phenotype.PIG-A gene abnormalities result in deficiencies of glycosylphosphatidylinositol-anchored proteins in PNH erythroblasts and granulocytes. The distribution of predominant PNH clones with PIG-A gene abnormalities is often heterogeneous between the cell types, suggesting that a clonal selection of PIG-A gene abnormalities occurs independently among various cell lineages during differentiation and maturation.

Regulation of functional activity of bone marrow hemopoietic stem cells by erythroid cells in mice

Transplantation of erythroid and bone marrow cells to irradiated mice stimulated exogenous colony formation. Pretreatment of erythroid cells with specific rabbit antiserum to erythroblasts abolished this effect. The reverse transcriptase polymerase chain reaction revealed the presence of mRNA for interleukin-1alpha, interleukin-1beta, interleukin-3, interleukin-6, and granulocyte-macrophage colony-stimulating factor in erythroid cells. Granulocyte-macrophage colony-stimulating factor was found in the conditioned medium from erythroid cells. Thus, erythroid cells stimulated colony-forming activity of bone marrow cells, which was probably mediated via cytokine synthesis (e.g., granulocyte-macrophage colony-stimulating factor).

Diagnosis and characterization of acute erythroleukemia subsets by determining the percentages of myeloblasts and proerythroblasts in 69 cases

Acute erythroleukemia (FAB M6) is a rare heterogeneous disease with an increase in red cell precursors and myeloblasts. Three subsets have been described: M6A (myeloblast-rich erythroleukemia); M6B (proerythroblast-rich erythroleukemia); and M6C (myeloblast- and proerythroblast-rich mixed variant). This study was undertaken to define and compare the clinical courses and survival outcomes among M6A, M6B, and M6C variants of erythroleukemia. Sixty-nine cases of M6 leukemia were categorized as consisting of >/=50% erythroid of all nucleated cells and M6A with >/=30% myeloblasts/nonerythroid component; M6B with >/=30% proerythroblasts/erythroid component; and M6C with >/=30% myeloblasts and >/=30% proerythroblasts. The demographics, cell type distribution, and survival (mean +/- sd) of these groups were compared. There were 32 M6A, 26 M6B, and 11 M6C patients. No significant difference was seen among the groups in age, sex, or treatment. Compared to M6A, both the M6B (P< 0.0001) and M6C (P< 0.0001) variants showed a statistically significant increase in the percentage of bone marrow erythroid cells, proerythroblasts, and the proerythroblasts/erythroid ratios. Comparing the groups for survival, M6B (3 +/- 3.6 months) versus M6A (25 +/- 28 months), P< 0. 002, and M6C (10 +/- 13 months) versus M6A, P< 0.01 had a poorer prognosis. Calculating the proerythroblasts as a component of total bone marrow erythroids provides a complimentary method for delineating the pure red cell erythroleukemia (M6B) and mixed variant (M6C), similar to that for the myeloid/erythroid (M6A) leukemia. Now that it is possible to delineate erythroleukemia subtypes, innovative treatments are indicated to target the malignant erythroid population, which is resistant to myeloid-based therapies.

Antigen of erythroblast (Ag-Eb): a membrane protein that may be an erythroid-specific transferrin receptor

Only a limited number of erythroid cell surface markers have been described in the literature. Ag-Eb was originally described as an erythroid-specific cell surface glycoprotein and could be used as an erythroid differentiation marker, but more recent studies suggest this localization is more widespread. From the data summarized in this review, it is hypothesized that Ag-Eb is a member of a subset of the transferrin receptor family and that it functions together with these receptors in the uptake and metabolism of iron, particularly at histo-hematic barriers.

[Levels of peripheral circulating nucleated erythrocytes in pregnant women for noninvasive prenatal diagnosis]

OBJECTIVE

Enrichment of nucleated red blood cells (NRBCs) from maternal blood for non-invasive prenatal diagnosis.

DESIGN

Pilot study.

SETTING

2nd Clinic of Paediatrics, University Hospital Motol, Prague, Czech Republic.

METHODS

Mononuclear cells were isolated from 13-28 ml of peripheral maternal blood between 13 and 37 weeks of gestation. Leukocytes from maternal peripheral blood were depleted from mononuclear cells by treatment with anti-CD14 and anti-CD45 microbeads and high-gradient magnetic cell separation (MACS) on VarioMACS. NRBCs were sorted from CD14-/CD45- fraction by positive selection using anti-CD71 microbeads on MiniMACS. All sorting steps were analysed by three-colour cytometric analysis with FACScan flow cytometer.

RESULTS

In 68 out of 78 pregnant woman (87%) NRBCs were found in range 2 x 10(5) - 1.02 x 10(6). NRBC were enriched with an average enrichment rate of 138-fold ranging from 4-526 fold. In our cohort of pregnant woman the number of isolated NRBCs was individual. We identified NRBCs from the 13th week of gestation.

CONCLUSION

The aim of the study is to establish and standardise the method of enrichment of NRBCs from maternal blood samples and verify the applicability of this alternative source for non-invasive prenatal diagnosis.

Erythroblastic synartesis: an auto-immune dyserythropoiesis

Erythroblastic synartesis is a rare form of acquired dyserythropoiesis, first described by Breton-Gorius et al in 1973. This syndrome is characterized by the presence of septate-like membrane junctions and "glove finger" invaginations between erythroblasts, which are very tightly linked together. This phenomenon, responsible for ineffective erythropoiesis, leads to an isolated severe anemia with reticulocytopenia. In the following report, we describe 3 new cases of erythroblastic synartesis associated with dysimmunity and monoclonal gammapathy. In all cases, the diagnosis was suggested by characteristic morphological appearance of bone marrow smears, and further confirmed by electron microscopy. Ultrastructural examination of abnormal erythroblast clusters showed that these cells were closely approximated with characteristic intercellular membrane junctions. The pathogenesis of the dyserythropoiesis was modeled in vitro using crossed erythroblast cultures and immunoelectron microscopy: when cultured in the presence of autologous serum, the erythroblasts from the patients displayed synartesis, whereas these disappeared when cultured in normal serum. Moreover, synartesis of normal erythroblasts were induced by the patient IgG fraction. Immunogold labeling showed that the monoclonal IgG were detected in, and restricted to, the synartesis. A discrete monoclonal plasmacytosis was also found in the patient bone marrow. The adhesion receptor CD36 appeared to be concentrated in the junctions, suggesting that it might be involved in the synartesis. These experiments indicated that a monoclonal serum immunoglobulin (IgG in the present cases) directed at erythroblast membrane antigen was responsible for the erythroblast abnormalities. Specific therapy of the underlying lymphoproliferation was followed by complete remission of the anemia in these cases.

A comparison of different density gradients and antibodies for enrichment of fetal erythroblasts by MACS

The enrichment of fetal cells, in particular fetal erythroblasts from the blood of pregnant women offers a promising non-invasive alternative for prenatal diagnosis. The purpose of this study was to compare the retrieval of erythroblasts by different density gradients and different antibodies against erythroid surface antigens, in both a model test system and in blood samples of pregnant women. We enriched erythroblasts from artificial mixtures of cord and adult blood (1:50) and from 16 ml of peripheral blood from pregnant women at a mean gestational age of 14+2 weeks. The yield of erythroblasts was calculated and compared using Wilcoxon's matched-pairs signed-rank test. In the artificial mixture most erythroblasts were retrieved using the heaviest density gradient (specific density of 1119) followed by antibody-labelled magnetic cell sorting (MACS). With anti-GPA the yield of erythroblasts from the artificial mixture was highest (9362.5 erythroblasts) compared with anti-CD36 (5164.3), anti-i (3455.2), anti-CD71 (3055.8) and HAE9 (2364.2). The difference between anti-GPA and anti-CD71, HAE9 and anti-i was significant (p=0.0277). The enrichment of erythroblasts from peripheral blood of pregnant women showed similar results. The yield of erythroblasts using anti-GPA was the highest. These results enable us to simplify our enrichment protocols to a single density gradient of 1119 specific density followed by MACS, with anti-GPA.

[The erythroblast antigen: a membrane protein bound to the erythroid form of the transferrin receptor?]

An interspecific marker of mammalian erythroid cells, which was called the erythroblast antigen, was identified in 1974, using polyclonal monospecific antibodies. Further studies have demonstrated the expression of this antigen in a variety of nonhemopoietic organs and tissues, which have the following common feature: they have a barrier location; that is, they are located at the boundary. It has been proposed that the erythroblast antigen participates directly or indirectly in the transport of various substances and specifically transport of iron. The present review deals with this topic.

The use of in vitro expanded erythroid cells in a model system for the isolation of fetal cells from maternal blood

The development of a non-invasive prenatal diagnostic test using fetal nucleated red blood cells (NRBCs) isolated from the maternal circulation is hampered by the low frequency of these cells in maternal blood, requiring extensive enrichment procedures before any analytical procedure can be performed. In order to improve and simplify these procedures, we have used in vitro expanded erythroid cells derived from male umbilical cord blood in a model system for the isolation of fetal NRBCs from maternal blood. Erythroblast cells were expanded in vitro to high cell numbers and were immunophenotypically identical to fetal NRBCs isolated from maternal blood. Magnetic activated cell sorting (MACS) isolation procedures were optimized using in vitro expanded male NRBCs diluted up to 1 in 400,000 with female peripheral blood mononucleated cells. The number of recovered male cells was determined using two-colour fluorescence in situ hybridization with X and Y chromosomal probes. Using this model system, an NRBC isolation technique is described. It is based on a one-step MACS enrichment protocol for CD71 positive cells, which showed a significant (Wilcoxon signed ranks test, p<0.05) two-fold higher yield of male NRBCs than previously described MACS methodologies, in which CD71 positive cells were enriched after depletion of other cell types. Application of these isolation strategies to maternal blood samples resulted in a similar improved enrichment of male fetal cells after the direct enrichment of CD71 positive cells.

Putative myeloma precursor cells expressing 2,6 sialic acid-modified antigens actually belong to the erythroid lineage

The Golgi enzyme alpha2,6-sialyltransferase modifies glycoconjugates by adding sialic acid. In lymphocytes, different epitopes that result from this modification have been identified by the B cell-related CDw75, CDw76, HB4 or HB6 Ab. We previously described positive staining with these Ab of a highly transferrin receptor-positive (CD71) cell type in the bone marrow of multiple myeloma patients. These cells were distinct from plasma cells, but did contain Ig of the same isotype and idiotype as seen in the plasma cells. We postulated a precursor role for this cell type in myeloma. Here, we report that this CD71+ (HB4/HB6/CDw75/CDw76)+ cell is an erythroid precursor cell instead. RT-PCR did not detect Ig mRNA, and from immuno electron microscopy Ig appeared to be endocytosed rather than synthesized by these cells. At their cell surface the erythroid/megakaryocytic markers CD36 and CD41, and the erythroid-specific glycophorin A can be detected, while haemoglobin can be detected antigenically in the cytoplasm. Finally, purified cells proliferate in vitro upon addition of erythropoietin. Uptake of Ig could be explained by the presence of Fc gammaRIII(CD16), which has also been found on other haematopoietic precursor cells.

Search for the optimal fetal cell antibody: results of immunophenotyping studies using flow cytometry

Fetal nucleated cells circulating in maternal peripheral blood are a noninvasive source of fetal DNA for prenatal genetic diagnoses. The successful isolation of fetal cells from maternal blood depends upon identification of differences between fetal and maternal cell surface antigen expression. To our best knowledge, a monoclonal antibody that binds only fetal blood cells has not yet been identified. We studied antigens recognized by six different monoclonal antibodies for their biologic expression on fetal blood cells as a function of gestational age, and compared their ability to bind fetal but not maternal cells. The results suggest a relationship between gestational age and nucleated cell surface antigen expression. The monoclonal antibodies FB3-2, H3-3, CD71 and 2-6B/6 are suitable reagents for first or early second trimester fetal cell isolation, although FB3-2 and H3-3 are more specific for fetal cells due to significantly lower expression of these antigens on maternal mononuclear cells. The observation that samples from fetuses with chromosome abnormalities or multiple structural anomalies express higher levels of these antigens indicates that these reagents will potentiate the detection of abnormal fetal cells in maternal blood samples.

Use of antibodies against the human antigen of erythroblasts for the detection of nucleated erythrocytes in the maternal circulation

In the present study, we tried to detect nucleated erythrocytes in maternal blood by means of the HAE9 antibody that binds to the antigen of erythroblasts (Ag-Eb) on nucleated erythroid cells. Umbilical cord blood and placental cells, which are known to contain a high number of nucleated erythrocytes, indeed demonstrated a high percentage of Ag-Eb-positive cells. In comparison, HAE9 stained up to 4.5% of the peripheral blood cells collected from pregnant women, but not those of nonpregnant women or normal men. These results, demonstrating a simple and reliable method for the identification of nucleated erythrocytes in the maternal circulation using the anti-Ag-Eb antibody, might open new possibilities for the detection of nucleated erythrocytes in maternal blood.

Expression of erythroblast antigen (AG-EB) in hematopoietic and non-hematopoietic mouse cells during pre- and postnatal ontogenesis. Immunocytochemical study using monoclonal antibody

It has been shown previously that erythroblast antigen (AG-EB) is an interspecies antigen expressed on the surface of nucleated red cells and reticulocytes. We have recently produced the monoclonal antibody MAE 15 that reacted specifically with murine epitope of AG-EB. Using MAE15 and immunocytochemical techniques on the light and electron microscopic levels the expression of AG-EB was studied in mouse embryonal and adult tissues. In mouse embryos AG-EB was revealed in erythroid cells of the yolk sac, liver and spleen, in epithelial cells of the intestine, salivary and thyroid glands as well as in the skin. The adult pregnant mice displayed AG-EB in cells of the yolk sac, decidua and trophoblast. The normal adult mice definitely expressed AG-EB not only in nucleated erythroid cells of the bone marrow and spleen but also in cells of non-hemopoietic organs and tissues: in epithelium of intestine, some glands and tubules of the kidney and testis; in endothelium of blood brain capillaries; in cells of the glandular layer of the epidermis; in insertion disks of myofibrils. Our findings suggest a possible transport role of AG-EB in different "barrier" cells.

Expression of sialosyl-Tn in colony-forming unit-erythroid, erythroblasts, B cells, and a subset of CD4+ cells

The epitopes Tn and sialosyl-Tn are expressed on erythrocytes of individuals with a very rare blood group, who often suffer from "Tn syndrome." We surveyed expression of Tn and sialosyl-Tn in normal blood cells, malignant transformed cells, and progenitor stem cells from bone marrow (BM). An anti-Tn antibody, IE3, and an anti-sialosyl-Tn antibody, TKH2, were used in this study. TKH2 reacted with erythroblasts, B cells, and a subset of CD4+ cells; but not with erythrocytes. Erythroblastic cell lines (K562, HEL, and UT7/EPO) and B-cell lines (Daudi, Raji, and B-cell lines transformed by Epstein-Barr virus) showed reactivity to TKH2. Similar results from the reactivity of TKH2 with transformed cells from leukemia patients and lymphoma patients were obtained; TKH2 reacted with blasts from erythroleukemia (M6; for 4 of 4 cases) and with lymphocytes from B-cell chronic lymphocytic leukemia (3 of 3), B-cell lymphoma (5 of 5), and CD4+ adult T-cell leukemia (4 of 4), but did not react with blasts from acute myeloid leukemia (M0 to M5; 0 of 22) or acute lymphoid leukemia (B-lymphoid leukemia, 0 of 11; T-lymphoid leukemia, 0 of 2; undifferentiated leukemia, 0 of 1). IE3 did not react with all of the tested cells. CD2-CD19-TKH2+ normal BM cells (BMC) contained blasts and various maturation stages of erythroblasts. The TKH2+ cells produced a large number of colony-forming unit-erythroid (CFU-E) colonies, whereas they produced a small number of burst-forming unit-erythroid colonies and CFU-granulocyte-macrophage colonies. CD34+ normal BMC did not express Tn and sialosyl-Tn. These findings suggest that sialosyl-Tn expresses in CFU-E to erythroblasts.

[The effect of cells presenting the erythroblast antigen on the natural suppressor activity of nonadhesive bone marrow cells]

Concanavalin A-induced proliferation of spleen cells of C57B1/6 mice was inhibited by syngeneic normal bone marrow cells. Elimination of Ag-Eb-positive cells by panning was shown to result in markedly reduced inhibitory activity of bone marrow cells. To evaluate the role of Ag-Eb in natural suppressor activity, bone marrow cells were preincubated with different dilutions of MAE-15 monoclonal antibody and then added to spleen cells. The inhibitory effect of bone marrow cells decreased with the increasing concentration of the monoclonal antibody in a dose-dependent manner and nearly disappeared at a concentration of MAE-15 of 150 m micrograms/ml and 300 m micrograms/ml. In control experiments, bone marrow cells were preincubated with antibodies non-reactive with Ag-Eb under the same conditions. It is concluded that the decrease of natural suppressor activity after incubation of bone marrow cells with MAE-15 monoclonal antibody is specific for anti-Ag-Eb antibodies.

Cytotoxic effect of ricin A-chain conjugates containing monoclonal antibodies against human erythroid cells

Selective elimination of human erythroblastoid cells by the conjugate of the A-chain of a plant toxin ricin (RA) and monoclonal antibody (MAb) HAE9 (IgM) directed against human erythroblast antigen (Ag-Eb) has been demonstrated. In comparative experiments, MAb HAE3 (IgM) against human glycophorin-A was used. On average, the conjugates obtained contained two A-chain molecules and one antibody molecule. Efficiency of cytotoxic action of native ricin and conjugates was compared both with the amount of binding sites on the surface of K562 cells and the internalization rate of these proteins. The association constants of the proteins proved to be almost the same (ka = 10(8) M-1). The ID50 values were 1.1 x 10(-11), 3.2 x 10(-10) and 3.1 x 10(-9) M for ricin, HAE9/RA and HAE3/RA, respectively. Ammonium chloride at a concentration of 10 mM increases the cytotoxic effect of the HAE9/RA conjugate approximately 10 times and does not change the activity of the HAE3/RA conjugate.

[Phagocytic activity of the central macrophage of erythroblastic islet in experimental inhibition and stimulation of erythropoiesis]

Phagocytic activity of the erythroblastic island central macrophage (EICM) was studied under normal conditions and in experimental inhibition and stimulation of erythropoiesis. Specific phagocytic activity (SPA) was estimated by the amount of latex particles absorbed by 1 EICM during 30-min incubation on plastic Petri dishes. SPA of CM in all the animals (no matter what experimental model was chosen) depended on EI affiliation to a certain class, with the maximum activity in EICM of the III class. SPA in EICM of the II-III classes in polycythemia animals was low. Blood loss significantly increased SPA in EICM of the II-IV classes of maturity. EICM of the I class showed a lower SPA that was, probably, due to the involvement of immature monocytes into EI organization.

Differential expression of non-major histocompatibility complex-restricted cytotoxicity in patients with granular lymphocyte-proliferative disorders associated with or unassociated with severe anemia

Of 27 patients with granular lymphocyte-proliferative disorders (GLPD), 18 patients had CD3+ T-cell-lineage GLPD (T-GLPD), and 9 patients had CD3-CD16+ natural killer (NK) cell-lineage GLPD (NK-GLPD). In 9 of the 18 patients with T-GLPD, severe anemia of less than or equal to 7.5 g/dl hemoglobin (mean 5.4 g/dl) and erythroid hypoplasia in the bone marrow developed, while the remaining 9 patients with T-GLPD and 9 patients with NK-GLPD exhibited hemoglobin levels of greater than or equal to 10.0 g/dl, and erythroid hypoplasia was not found. The number of leukocytes, neutrophils, lymphocytes or granular lymphocytes in the peripheral blood, or the percentage of lymphocytes in the bone marrow did not differ significantly between the patients with T-GLPD associated with severe anemia and those with T-GLPD not associated with severe anemia, and the immunophenotypes of peripheral blood mononuclear cells (PBMC) were not significantly different either. However, when non-major histocompatibility complex (MHC)-restricted cytotoxicity was assayed with PBMC, T-GLPD patients with severe anemia and NK-GLPD patients exhibited significantly higher levels of non-MHC-restricted cytotoxicity than T-GLPD patients without severe anemia. Because PBMC obtained from T-GLPD patients with severe anemia were shown not to lyse erythroblasts directly, the possibility that patient PBMC lyse erythroblasts in the bone marrow and thus cause anemia seems unlikely. The pathogenesis of anemia in GLPD was discussed.

Erythroblast- and erythrocyte-bound antibodies in alpha and beta thalassaemia syndromes

Thirty-five Thai patients with various alpha-thalassaemia (alpha-thal 1/alpha-thal 2, alpha-thal 1/HbCS, HbCS/HbCS) and beta-thalassaemia (beta-thal/HbE, severe and mild form, HbE/HbE) syndromes were examined for the presence of immunoglobulins and C3d on o-tolidine positive erythroblasts in the bone marrow, and for the amounts of IgG of some specificities bound to circulating erythrocytes. In mild, but not in severe beta-thal/HbE and in alpha-thalassaemia, the percentages of Ig-positive erythroblasts were significantly higher than in controls and correlated well with the percentage of IgG-positive erythroblasts. By contrast, the percentages of IgM and C3d positive erythroblasts were low and similar in thalassaemic and control marrows. A substantial proportion of thalassaemic patients showed more erythrocyte-bound IgG than controls, but statistically significant elevations were seen only in severe beta-thal/HbE. Within a particular syndrome erythrocyte-bound IgG was more abundant in splenectomized than non-splenectomized subjects. It showed specificity for spectrin in some beta-thalassaemic patients and for band 3 protein in several individuals with alpha- or beta-thalassaemia. The results suggest that IgG antibodies play a role in the haemolysis of thalassaemia and that they are likely to be involved in the ineffective erythropoiesis in at least some of the syndromes studied.

[Erythroblast antigen expression in murine hematopoietic and nonhematopoietic cells. 2. An immunofluorescent study in pre- and postnatal ontogeny using monoclonal antibodies]

The expression of erythroblast antigen (Ag-Eb) in cell membranes during pre- and postnatal mouse development was studied by immunofluorescence using the monoclonal antibody MAE-15. Ag-Eb was detected in embryonic liver, spleen, epithelia of intestine, various glands and skin, as well as in extraembryonic tissues (yolk sac and trophoblast). In pregnant mice positive immunofluorescence was observed in placenta and on the surface of decidual cells in uterus. In adult non-pregnant mice Ag-Eb expression was detected not only in membranes of erythroid cells, but also in non-hemopoietic tissues, such as epithelia of various glands, intestine, kidney and testis, brain endothelium, basal layer of epidermis, and intercalated discs of the heart muscle. A possible role of Ag-Eb in processes of cell transport is discussed.

Natural serum antibodies which bind to damaged erythroblasts: isotypes and light-chain composition

Dimethyl-sulphoxide-induced Friend leukaemia erythroblasts (IFLE) which had been damaged by treatment with inhibitors of protein synthesis (cycloheximide, puromycin) were incubated with normal mouse serum or with doubling dilutions of it. The erythroblasts were subsequently tested for their binding of natural antibodies of all the major immunoglobulin (Ig) isotypes and both light-chain types, using Fc- and light-chain-specific FITC-immunoconjugates, and flow cytometry. After short-term (4-h) exposure of IFLE to puromycin, some binding of IgG but not of IgM or IgA could be demonstrated. By contrast, prolonged (17-h) exposure of IFLE to cycloheximide or puromycin resulted in their reaction with antibodies of all major isotypes (IgM, IgG1, IgG2a, IgG2b, IgG3, IgA) containing kappa-light chains. Under these conditions of damage the percentage of IgM- or IgG-binding IFLE significantly exceeded that of IgA-reactive cells. Moreover, the percentage of damaged IFLE which bound IgG2a or IgG3 was greater than that of cells which bound IgG1 or IgG2b. The percentage of damaged IFLE which bound a certain Ig-isotype did not correlate with the concentration of that Ig-isotype in normal mouse serum. The results suggest that natural antibodies of all major isotypes containing kappa-light chains bind specifically to severely damaged IFLE and could facilitate their interaction with macrophages in a concerted manner.

Identification of two additional v-sea-encoded proteins in avian erythroblastosis virus, S13-infected fibroblasts

Rabbit antibodies prepared against a v-sea-encoded polypeptide expressed in bacteria were used to characterize the v-sea-encoded proteins in cells transformed by the avian erythroblastosis virus, S13. In addition to the two previously described v-sea-encoded proteins, gp155 and gp70, two additional proteins were identified of molecular weights 38,000 and 36,000 Da. Interestingly, these two proteins were found only in fibroblasts infected with the S13 virus and not in S13-transformed erythroid cells. These two proteins were phosphoproteins, but, unlike the two previously characterized v-sea-encoded proteins, they did not appear to be modified by the addition of N-linked sugars. Possible mechanisms for the biosynthesis of these two new proteins are discussed.

Lymphoblastic crisis of chronic myelogenous leukemia. Hand mirror variant

We present, to our knowledge, the first extensively studied case of lymphoid L2 blast crisis of chronic myelogenous leukemia with a hand mirror cell (HMC) variant. Special stains revealed the leukemic cells to be terminal deoxynucleotidyl transferase positive by immunofluorescence and cytochemically positive for alpha-naphthyl acetate esterase and acid phosphatase (diffuse granular). Immunophenotyping identified the major leukemic cell population as B-cells that expressed CD10+, CD19+, and HLA-DR+. It was not possible to separate the HMC and the non-HMC leukemic population by gating various cell populations, dual staining, cytochemistry, or by terminal deoxynucleotidyl transferase. Gene rearrangements were observed in both Ig heavy-chain alleles and one T-cell antigen receptor gamma-subunit allele. The rearrangements occupied all of the cells, indicating that the HMC and non-HMC were of a common clonal origin. The patient had a mosaic karyotype, with 90% of the cells having t(9;22), t(8;14), and t(9;15) translocations, an additional chromosome 8, and deleted chromosomes 9 and 15. Antibodies to simian sarcoma-associated virus and baboon endogenous virus were isolated in the patient's peripheral blood plasma.

Murine monoclonal antibodies against a unique determinant of erythrocytes, related to Rh and U antigens: expression on normal and malignant erythrocyte precursors and Rhnull red cells

Three murine monoclonal antibodies (Mabs) MB-2D10, LA-18.18 and LA-23.40 were prepared. They reacted with red cells of all common and most rare blood-group phenotypes, with the exception of those of the RhnullU negative and RhmodU negative phenotypes. So far, only a single example of an alloantibody (Duclos or anti-Rh38) of a similar specificity has been found. Serological studies indicated that the Mabs were probably not directed against an antigenic determinant of Rh polypeptides, the LWab glycoprotein or glycophorin B, all structures absent from or aberrantly expressed on Rhnull red cells. The antigen was found to be erythrocyte-specific, and was also present on pro-erythroblasts, erythroblasts and malignant erythroblastoid cells but not on erythroid progenitors in the bone marrow. The Mabs were found to block each other in an immune rosette method and are thus probably directed against the same epitope or against neighbouring epitopes on the same structure. In immunochemical studies, MB-2D10 precipitated the 30-32 kDa Rh polypeptides from red cell membranes and a protein or proteins which formed diffuse and overlapping bands in SDS-polyacrylamide gel electrophoresis, with Mrs of 40-200 kDa (probably the Rh-related glycoproteins). Under certain experimental conditions glycophorin B appeared to be coprecipitated. The 2D10 structure, detected by the Mabs, seems to be part of a complex of proteins and/or glycoproteins, which includes Rh polypeptides, the LWab glycoprotein and glycoproteins recognized by various Mabs with Rh-related specificities. In the red cell membrane, the complex may be associated with glycophorin B.

A new murine monoclonal antibody for the diagnosis of erythroleukemia

The authors have developed a murine monoclonal antibody, RC-82.4, against an antigen expressed by a human erythroleukemia cell line OCI-MIR. The antibody reacts with an antigen expressed by proerythroblasts, normoblasts, and some reticulocytes but not expressed in erythrocytes, granulocytes, monocytes, megakaryocytes, plasma cells, or lymphocytes. The authors have established an immunocytochemical method for studying bone marrow smears with RC-82.4. By studying bone marrow smears from 11 patients with M-6 erythroleukemia and 104 patients with various other hematologic and nonhematologic malignancies, the authors have found that RC-82.4 has great sensitivity and specificity in recognizing erythroid differentiation in blasts. The authors have used RC-82.4 and antihemoglobin antibodies to identify erythroblasts in acute and secondary acquired cases of erythroleukemia that would have been unclassifiable by morphologic and all other conventional cytochemical and immunocytochemical criteria.