Autoreactive erythroid progenitor-T suppressor cells in the pure red cell aplasia associated with thymoma and panhypogammaglobulinemia

Identification and Characterization of Non-Coding RNAs in Thymoma

BACKGROUND Thymoma is the most common tumor of the anterior mediastinum, and can be caused by infrequent malignancies arising from the epithelial cells of the thymus. Unfortunately, blood-based diagnostic markers are not currently available. High-throughput sequencing technologies, such as RNA-seq with next-generation sequencing, have facilitated the detection and characterization of both coding and non-coding RNAs (ncRNAs), which play significant roles in genomic regulation, transcriptional and post-transcriptional regulation, and imprinting and epigenetic modification. The knowledge about fusion genes and ncRNAs in thymomas is scarce. MATERIAL AND METHODS For this study, we gathered large-scale RNA-seq data belonging to samples from 25 thymomas and 25 healthy thymus specimens and analyzed them to identify fusion genes, lncRNAs, and miRNAs. RESULTS We found 21 fusion genes, including KMT2A-MAML2, HADHB-REEP1, COQ3-CGA, MCM4-SNTB1, and IFT140-ACTN4, as the most frequent and significant in thymomas. We also detected 65 differentially-expressed lncRNAs in thymomas, including AFAP1-AS1, LINC00324, ADAMTS9-AS1, VLDLR-AS1, LINC00968, and NEAT1, that have been validated with the TCGA database. Moreover, we identified 1695 miRNAs from small RNA-seq data that were overexpressed in thymomas. Our network analysis of the lncRNA-mRNA-miRNA regulation axes identified a cluster of miRNAs upregulated in thymomas, that can trigger the expression of target protein-coding genes, and lead to the disruption of several biological pathways, including the PI3K-Akt signaling pathway, FoxO signaling pathway, and HIF-1 signaling pathway. CONCLUSIONS Our results show that overexpression of this miRNA cluster activates PI3K-Akt, FoxO, HIF-1, and Rap-1 signaling pathways, suggesting pathway inhibitors may be therapeutic candidates against thymoma.

Anemia of Central Origin

Hypoproliferative anemia results from the inability of bone marrow to produce adequate numbers of red blood cells. The list of conditions that cause hypoproliferative anemia is long, starting from common etiologies as iron deficiency to rarer diagnoses of constitutional bone marrow failure syndromes. There is no perfect diagnostic algorithm, and clinical data may not always clearly distinguish "normal" from "abnormal", yet it is important for practicing clinicians to recognize each condition so that treatment can be initiated promptly. This review describes diagnostic approaches to hypoproliferative anemia, with particular emphasis on bone marrow failure syndromes.

Autoimmune cytopenias in chronic lymphocytic leukemia

The clinical course of chronic lymphocytic leukemia (CLL) may be complicated at any time by autoimmune phenomena.The most common ones are hematologic disorders, such as autoimmune hemolytic anemia (AIHA) and immune thrombocytopenia (ITP). Pure red cell aplasia (PRCA) and autoimmune agranulocytosis (AG) are, indeed, more rarely seen. However, they are probably underestimated due to the possible misleading presence of cytopenias secondary to leukemic bone marrow involvement or to chemotherapy cytotoxicity. The source of autoantibodies is still uncertain, despite the most convincing data are in favor of the involvement of resting normal B-cells. In general, excluding the specific treatment of underlying CLL, the managementof these complications is not different from that of idiopathic autoimmune cytopenias or of those associated to other causes. Among different therapeutic approaches, monoclonal antibody rituximab, given alone or in combination, has shown to be very effective.

Good's syndrome remains a mystery after 55 years: A systematic review of the scientific evidence

Good syndrome (GS) is a rare association of thymoma and immunodeficiency first described more than 50 years ago. However, this syndrome still remains a mystery to clinicians. We systematically reviewed all the clinical, laboratory and immunologic findings from 152 patients with Good syndrome. The syndrome has a worldwide distribution and approximately half of the cases (47%) have been described in Europe. The diagnosis of thymoma preceded the diagnosis of hypogammaglobulinemia, infection, or diarrhea in 42% of patients whereas in 38% of patients the diagnoses were made almost simultaneously within 2 months of each other. We found significant mortality in patients with this syndrome (44.5%). Astute clinical acumen and increased awareness about the clinical and immunological profile of this syndrome may increase early recognition of this syndrome and prevent mortality. Further studies are needed to elucidate this clinical entity.

Diagnosis and management of acquired pure red cell aplasia

Pure red cell aplasia is a syndrome characterized by a severe normocytic anemia, reticulocytopenia, and absence of erythroblasts from an otherwise normal bone marrow. Although the causes and natural course of this syndrome are variable and although the anemia in some patients can be managed by treatment of an underlying inflammatory or neoplastic disease, the pathogenesis of a large number of cases is autoimmune, including those associated with thymoma, and are best managed with immunosuppressive therapy.

Chronic Lymphocytic Leukemia-Associated Pure Red Cell Aplasia

Pure red cell aplasia (PRCA) is a well-known marrow failure which may be acquired or constitutional/congenital, as the Diamond-Blackfan syndrome. Acquired PRCA may show as a primary hematological disorder or secondary to an associated disease, infection or drug. PRCA rarely complicates chronic lymphocytic leukemia (CLL), may occur anytime in the course of the disease and, in this context, it is a minority of total PRCA. Anemia due to PRCA in CLL patients must be carefully evaluated and differentiated from other causes (autoimmune hemolytic anemia, neoplastic lymphocyte infiltration of bone marrow, chemotherapy) that require a different therapeutic approach. PRCA is thought to be an immunologically mediated disorder, but there is no uniformity in the setting of the management. Immunosuppressive therapy is frequently given, such as steroids and cyclosporin-A. Recently, anecdotal cases have been published on the effectiveness of monoclonal antibodies rituximab and alemtuzumab.

Thymoma: Benign Appearance, Malignant Potential

Thymoma is a rare tumor with a largely indolent growth pattern. It does, however, have malignant potential as a result of its ability to invade locally and metastasize regionally. Often associated with a number of immune- and nonimmune-mediated paraneoplastic syndromes, patient outcomes are directly related to stage of disease and the ability to achieve a complete surgical resection. Surgery is the mainstay of treatment, with adjuvant radiation recommended for invasive thymoma. Sensitive to both chemotherapy and radiation, durable responses are achievable in incompletely resected and inoperable patients. We present two cases of thymoma followed by a general discussion with an emphasis on treatment for both early and advanced-stage disease.

Early autoimmune complications after thymomectomy in a patient with interstitial lung disease. Case report

Thymoma has been associated with a variety of autoimmune disorders. We report a case of myasthenia gravis and pancytopenia in a 53-year-old man with lymphoepithelial thymoma and interstitial lung disease. Preoperative examination revealed neither hematologic abnormality nor myasthenia gravis. The patient had enteritis prior to thymomectomy, sternal infection in the first month of operation, and urinary infection at the third month. About three months after thymomectomy, he required mechanical ventilation support due to myasthenia gravis-related respiratory failure. One month later, a rapidly progressing pancytopenia developed. The patient died within two weeks of overwhelming septicemia unresponsive to treatment with antibiotics and steroids. The possible onset of myasthenia gravis or pancytopenia after thymomectomy should be kept in mind during follow-up. Recurrent infections in the early stages of thymomectomy may suggest a lethal onset of pancytopenia.

Defect in the lymphoid compartment might account for CD8+-mediated effects in the pathophysiology of pure red cell aplasia

Pure red cell aplasia (PRCA) is a rare hematological syndrome characterized by the lack of red cell progenitors in an otherwise normocellular bone marrow. Many agents and mechanisms have been implicated in the pathophysiology of PRCA, including immune-mediated dysfunctions. This report describes three patients with PRCA with unknown underlying cause and showed that for each, increases in CD8+ cells blunted the maturation of early erythroid (BFU-E). Each patient subsequently responded to immunosuppressive therapy. Peripheral blood mononuclear cells from age- and sex-matched healthy controls showed comparable distribution of CD3, CD4 and CD16, but significant increase in CD8 and decreased CD19. The distribution of lymphocyte subsets correlated with mitogen responses, but showed no difference in allogeneic responses when compared to controls. The adherent population in PRCA is important for mediating the hyper-immune state of patients, when IL-2 levels were used as readout. There was a trend for decreased BFU-E in patients, but marked reduction for late erythroid progenitors (CFU-E). CD8+ cells from PRCA blunted the maturation of BFU-E, despite increasing erythropoietin concentrations. These results strongly suggest that there are defects in the lymphoid compartment that feedback on the erythroid lineage of PRCA.

Fatal subacute cytomegalovirus encephalitis associated with hypogammaglobulinemia and thymoma

Parathymic syndromes are systemic disorders that occur in association with thymoma. One such parathymic syndrome, hypogammaglobulinemia, was initially identified by Good in 1954 and has been referred to as Good syndrome. Patients with this syndrome develop a variety of recurrent infections due to the associated immunodeficiency. We describe a patient with cytomegalovirus encephalitis associated with Good syndrome and discuss the pathologic findings present on autopsy. The possibility of a cytomegalovirus infection should be considered early in the evaluation of patients with Good syndrome if appropriate clinical symptoms are present.

Autoimmune disorders of erythropoiesis

Immune-mediated disorders of erythropoiesis can result in acquired severe anemia, low reticulocyte counts, and bone marrow exhibiting pure red cell aplasia or ineffective erythropoiesis. Erythropoiesis can be suppressed or impaired by humoral or cellular mechanisms. In vitro inhibition of erythroid colony growth by immunoglobulins or lymphocytes can be a strong argument for the immune origin of the disease. Classical etiologies are thymoma and hematologic malignancies such as chronic lymphocytic leukemia (CLL). Clonal proliferation of T cells has been incriminated. Recently, acquired circulating autoantibodies directed against erythropoietin have been detected in a case of pure red cell aplasia. Autoimmune mechanisms have also been detected or suggested in synartesis and in Fas-associated dyserythropoiesis, two distinct syndromes recently described where morphologic abnormalities specific to the erythroid lineage illustrate ineffective erythropoiesis.

Infections in patients with immunodeficiency with thymoma (Good syndrome). Report of 5 cases and review of the literature

Immunodeficiency with thymoma (Good syndrome, GS) is a rare, adult-onset condition that is characterized by thymoma, hypogammaglobulinemia, and low numbers of peripheral B cells. CD4+ T lymphopenia and an inverted CD4:CD8+ T-cell ratio may be present. Here we report 5 patients with GS and infectious complications who were seen at 3 institutions between 1983 and 1999. Three patients had recurrent sinopulmonary infections, 3 had severe cytomegalovirus (CMV) disease, and 1 had Pneumocystis carinii pneumonia. Review of the literature identified 46 other reports of infections in GS patients. The infections reported in all 51 patients included recurrent sinopulmonary infection (19 cases with documented respiratory pathogens), generally with encapsulated bacteria, most often Haemophilus influenzae (11 cases); CMV disease (5 cases); bacteremia (7 cases); oral or esophageal candidiasis (6 cases); persistent mucocutaneous candidiasis (5 cases); chronic diarrhea (5 cases with documented stool pathogens); urinary tract infections (4 cases); P. carinii pneumonia (3 cases); tuberculosis (2 cases); Kaposi sarcoma (1 case); disseminated varicella (1 case); candidemia (1 case); wound infection with Clostridium perfringens (1 case); Mycoplasma arthritis (1 case); and other infections. Patients with GS present with a spectrum of sinopulmonary infections and pathogens similar to common variable immunodeficiency (CVID). Compared with patients with CVID, opportunistic infections, including severe CMV disease, P. carinii pneumonia, and mucocutaneous candidiasis, appear to be more common in patients with GS, and patients with GS may have a worse prognosis. GS should be ruled out in patients with thymoma or CVID who develop severe, especially opportunistic, infections. Treatment with intravenous immune globulin is recommended for all patients with GS.

Macrocytic anemia and thrombocytosis associated with thymoma: a case report

Thymomas are often associated with autoimmune disorders. We report on a 45-year-old female patient with thymoma and hypogammaglobulinemia (Good's syndrome) who developed symptomatic macrocytic anemia (Hb 4.4 g/dl, MCV 112 fl) and thrombocytosis (Plt 442 G/l). Besides hypogammaglobulinemia (IgG 589 mg/dl), an inverted ratio of CD4(+)/CD8(+) cells was seen. The bone marrow biopsy showed a slightly hypercellular bone marrow with normal granulopoiesis, normal megakaryopoiesis and a mild dyserythropoiesis without any ring-sideroblasts. The in-vitro stem cell culture from the bone marrow revealed an atypical growth of macroclusters, reduced BFU-E and CFU-GEMM colony growth, whereas the CFU-GM colony growth was within the normal range. The chromosomal analysis showed a normal karyotype. The plasma vitamin B(12) and folate levels were within normal ranges, and we could not detect any autoantibodies. These findings excluded the differential diagnoses pure red cell aplasia (PRCA) and pernicious anemia. After resection of the thymoma of mixed cell type, the macrocytic anemia and thrombocytosis disappeared. The clinical course was complicated by a cerebral palsy and a life-threatening fungal septicemia after surgery. In the third year after thymectomy, hyporegenerative macrocytic anemia and thrombocytosis reappeared and an immunosuppressive treatment with prednisolone (1 mg/kg BW) was started. After initiation of the prednisolone therapy, reticulocyte counts increased and macrocytic anemia as well as thrombocytosis disappeared. The normalization of these laboratory parameters during glucocorticoid therapy suggests that in rare cases the constellation of macrocytic anemia, thrombocytosis and hypogammaglobulinemia may be due to an underlying immunologic mechanism.

New Insights into the Pathophysiology of Acquired Cytopenias

This review addresses three related bone marrow failure diseases, the study of which has generated important insights in hematopoiesis, red cell biology, and immune-mediated blood cell injury. In Section I, Dr. Young summarizes the current knowledge of acquired aplastic anemia. In most patients, an autoimmune mechanism has been inferred from positive responses to nontransplant therapies and laboratory data. Cytotoxic T cell attack, with production of type I cytokines, leads to hematopoietic stem cell destruction and ultimately pancytopenia; this underlying mechanism is similar to other human disorders of lymphocyte-mediated, tissue-specific organ destruction (diabetes, multiple sclerosis, uveitis, colitis, etc.). The antigen that incites disease is unknown in aplastic anemia as in other autoimmune diseases; post-hepatitis aplasia is an obvious target for virus discovery. Aplastic anemia can be effectively treated by either stem cell transplantation or immunosuppression. Results of recent trials with antilymphocyte globulins and high dose cyclophosphamide are reviewed.

Dr. Abkowitz discusses the diagnosis and clinical approach to patients with acquired pure red cell aplasia, both secondary and idiopathic, in Section II. The pathophysiology of various PRCA syndromes including immunologic inhibition of red cell differentiation, viral infection (especially human parvovirus B19), and myelodysplasia are discussed. An animal model of PRCA (secondary to infection with feline leukemia virus [FeLV], subgroup C) is presented. Understanding the mechanisms by which erythropoiesis is impaired provides for insights into the process of normal red cell differentiation, as well as a rational strategy for patient management.

Among the acquired cytopenias paroxysmal nocturnal hemoglobinuria (PNH) is relatively rare; however, it can pose formidable management problems. Since its first recognition as a disease, PNH has been correctly classified as a hemolytic anemia; however, the frequent co-existence of other cytopenias has hinted strongly at a more complex pathogenesis. In Section III, Dr. Luzzatto examines recent progress in this area, with special emphasis on the somatic mutations in the PIG-A gene and resulting phenotypes. Animal models of PNH and the association of PNH with bone marrow failure are also reviewed. Expansion of PNH clones must reflect somatic cell selection, probably as part of an autoimmune process. Outstanding issues in treatment are illustrated through clinical cases of PNH. Biologic inferences from PNH may be relevant to our understanding of more common marrow failure syndromes like myelodysplasia.

New Insights into the Pathophysiology of Acquired Cytopenias

This review addresses three related bone marrow failure diseases, the study of which has generated important insights in hematopoiesis, red cell biology, and immune-mediated blood cell injury. In Section I, Dr. Young summarizes the current knowledge of acquired aplastic anemia. In most patients, an autoimmune mechanism has been inferred from positive responses to nontransplant therapies and laboratory data. Cytotoxic T cell attack, with production of type I cytokines, leads to hematopoietic stem cell destruction and ultimately pancytopenia; this underlying mechanism is similar to other human disorders of lymphocyte-mediated, tissue-specific organ destruction (diabetes, multiple sclerosis, uveitis, colitis, etc.). The antigen that incites disease is unknown in aplastic anemia as in other autoimmune diseases; post-hepatitis aplasia is an obvious target for virus discovery. Aplastic anemia can be effectively treated by either stem cell transplantation or immunosuppression. Results of recent trials with antilymphocyte globulins and high dose cyclophosphamide are reviewed.

Dr. Abkowitz discusses the diagnosis and clinical approach to patients with acquired pure red cell aplasia, both secondary and idiopathic, in Section II. The pathophysiology of various PRCA syndromes including immunologic inhibition of red cell differentiation, viral infection (especially human parvovirus B19), and myelodysplasia are discussed. An animal model of PRCA (secondary to infection with feline leukemia virus [FeLV], subgroup C) is presented. Understanding the mechanisms by which erythropoiesis is impaired provides for insights into the process of normal red cell differentiation, as well as a rational strategy for patient management.

Among the acquired cytopenias paroxysmal nocturnal hemoglobinuria (PNH) is relatively rare; however, it can pose formidable management problems. Since its first recognition as a disease, PNH has been correctly classified as a hemolytic anemia; however, the frequent co-existence of other cytopenias has hinted strongly at a more complex pathogenesis. In Section III, Dr. Luzzatto examines recent progress in this area, with special emphasis on the somatic mutations in the PIG-A gene and resulting phenotypes. Animal models of PNH and the association of PNH with bone marrow failure are also reviewed. Expansion of PNH clones must reflect somatic cell selection, probably as part of an autoimmune process. Outstanding issues in treatment are illustrated through clinical cases of PNH. Biologic inferences from PNH may be relevant to our understanding of more common marrow failure syndromes like myelodysplasia.

Clinical value of bone marrow cultures in childhood pure red cell aplasia

PURPOSE

We assessed the value of marrow cultures for defining the pathophysiology, diagnosis, and therapeutic response to immunosuppressive therapy in childhood pure red cell aplasia (PRCA).

PATIENTS AND METHODS

Patients were evaluated either at diagnosis (n = 23) or at the time of treatment failure (n = 2). Twelve patients had transient erythroblastopenia of childhood (TEC), 4 had Diamont-Blackfan anemia (DBA), and 9 had acquired sustained PRCA (A-Su-PRCA). Bone marrow mononuclear cells were cultured with combination of human recombinant (rhu) erythropoietin (EPO), granulocyte monocyte colony stimulating factor (GM-CSF), granulocyte colony stimulating factor (G-CSF), Interleukin 3 (IL-3), either with or without stem cell factor (SCF), and burst forming unit of erythroid (BFU-E) growth was assessed.

RESULTS

The combination of growth factors without SCF failed to induce any erythropoiesis (BFU-E < 10/10(5) mononuclear cells) in 10 patients (2 with TEC, 2 with DBA, and 6 with A-Su-PRCA), although the growth of erythroid colonies was substantially lower in the remaining patients than in controls (45.5 +/- 15.4 versus 91.7 +/- 12.7, p < 0.05). Addition of SCF restored erythropoiesis in all but 6 patients (5 with A-Su-PRCA and 1 with DBA). Five of 6 nonresponders did not respond to any immunomodulating therapy; of the 5, 3 had or developed some evidence of myelodysplasia.

CONCLUSION

Our data indicate that in vitro colony studies might prove to be a useful diagnostic tool, because erythropoiesis' poor response to growth factors, including SCF, may suggest the diagnosis of myelodysplasia. Moreover, it may have predictive value; in cases of PRCA, regardless of etiology, poor growth of erythropoietic colonies may predict refractoriness to immunomodulating therapy.

Thymoma associated with CD4+ lymphopenia, cytomegalovirus infection, and Kaposi's sarcoma

A case of thymoma with associated opportunistic infections, CD4/CD8 T-lymphocyte imbalance, low CD4-positive T-lymphocyte counts and Kaposi's sarcoma (KS) without HIV infection is reported. Cytomegalovirus inclusions were identified in the nuclei of some KS spindle and endothelial cells. It is known that KS has a high prevalence in AIDS patients and has occasionally been associated with other causes of immunosuppression. In previous studies, coexisting KS and thymoma were related to myasthenia gravis, corticosteroid treatment and excess CD8-positive T-lymphocyte counts. More recently an imbalance between CD4 and CD8 positive T lymphocytes has been identified in association with thymoma. The present case suggests that there may be a relationship between thymoma, CD4-positive lymphopenia, and KS.

Immune mediated agranulocytosis and anemia associated with thymoma

Thymoma has been associated with a variety of autoimmune disorders. We report a case of agranulocytosis and anemia in a 68-year-old woman with a spindle cell thymoma. She was unresponsive to treatment with antibiotics, granulocyte-colony stimulating factor (G-CSF), prednisone, and high-dose intravenous immunoglobulin. Serial bone marrow examinations on this therapy showed progression from a cellular marrow with mild myeloid and erythroid hyperplasia and lymphocytosis, to granulocyte aplasia and severe erythroid hypoplasia. Her serum contained granulocyte-specific antibodies and inhibited the growth in culture of her own marrow cells and marrow cells from a normal donor. An IgG fraction from her serum also inhibited the growth of marrow cells. Although the patient's spindle cell thymoma was surgically removed, she remained neutropenic. She was treated with six plasma exchanges followed by 1,000 milligrams of intravenous cyclophosphamide 2 days after the final plasma exchange and daily G-CSF. Three weeks later her peripheral blood showed marked leukocytosis with pronounced neutrophilia and a left shift. Although her agranulocytosis resolved, she died of fungal sepsis. This case demonstrates that aggressive plasma exchange and immunosuppressive therapy may benefit patients with agranulocytosis associated with thymoma.

Pancytopenia associated with thymoma resolving after thymectomy and immunosuppressive therapy. Case report

In a 43-year-old woman, pancytopenia accompanying thymoma persisted after thymectomy, requiring weekly blood transfusions, and did not respond to prednisone 50 mg/day. Cyclosporine 10 mg/kg/day plus prednisone 20 mg/day for a month gradually corrected the blood parameters. Thirty months later the patient is well and haematologically stable.

A B cell line from a patient with pure red cell aplasia produces an immunoglobulin that suppresses erythropoiesis

A 4-year-old boy with pure red cell aplasia was investigated. Immunophenotypic analysis of peripheral blood lymphocytes revealed a marked increase of CD20+ cells, which fell from 25.9% in the active stage to 9.7% in remission. The plasma contained a suppressive activity against CFU-e and BFU-e formation by the patient's bone marrow cells, which disappeared when the disease went into remission. Prednisone (2 mg/kg/day) therapy was tried for 5 weeks, but produced no improvement. Subsequently, high-dose gamma-globulin therapy induced complete remission of anemia. A lymphoblastoid B cell line obtained from the patient before therapy produced a factor that suppressed erythropoiesis but not granulopoiesis. The suppressive activity resided in the immunoglobulin fraction and was adsorbed by an anti-immunoglobulin column. These results indicate that expansion of B cells producing an immunoglobulin which suppressed erythropoiesis was involved in the pathogenesis of the disease in this patient.

Response of agranulocytosis to thymectomy in a patient with thymoma and chronic lymphocytic leukemia

A patient with chronic lymphocytic leukemia presented with recurrent episodes of severe neutropenia. This neutropenia was initially responsive to prednisone but eventually became refractory. A spindle-cell thymoma was diagnosed and resected with dramatic improvement in his granulocytopenia. Both autologous and heterologous granulocyte macrophage colony growth were clearly inhibited by the patient's serum. This is the first reported case of severe granulocytopenia associated with a thymoma that seemed to be reversed following thymectomy.

Demonstration of three distinct immunological disorders on erythropoiesis in a patient with pure red cell aplasia and autoimmune haemolytic anaemia associated with thymoma

A patient with pure red cell aplasia (PRCA) and autoimmune haemolytic anaemia (AIHA), associated with a thymoma which had already been removed, was studied in order to investigate the pathogenesis of PRCA and AIHA. The autoantibody eluted from the surface of the patient's red blood cells (RBC) reacted with the large E antigen of the Rh complex. Immunoglobulin-G (IgG) purified from the patient's serum suppressed CFU-E and BFU-E but not CFU-GM colony formation in the presence of complement. This antibody was not adsorbed with large E antigen. T-lymphocytes in the bone marrow suppressing autologous CFU-E and BFU-E colonies were demonstrated. Thus, three distinct immunological disorders on erythropoiesis were present in this patient with PRCA and AIHA associated with thymoma in a thymectomized state.

Enrichment of haemopoietic progenitor cells from the marrow of patients with myelodysplasia

Myeloid and erythroid progenitors from myelodysplastic marrows have been separated from accessory cell populations likely to influence their in-vitro growth. Myeloid colony-forming cells were enriched 23-fold and erythroid progenitors 5-7-fold but, in both cases, retained their abnormal growth characteristics. After enrichment and removal of lymphocytes and monocytes, erythroid burst formation became markedly more dependent on the addition of 5637 bladder carcinoma conditioned medium as an exogenous source of haemopoietic growth factors. This suggests that lymphocytes and monocytes usually support erythropoiesis in cultures of myelodysplastic marrow and demonstrates that erythroid burst-forming progenitor cells from myelodysplastic patients can respond to these populations in vitro. Haemopoietic failure in myelodysplasia appears to result from a defect within the preleukaemic clonogenic cell, rather than from an aberration in exogenous factors. The procedure outlined here can be used as a first step towards the isolation of these abnormal progenitors.