Serum erythropoietic inhibitors in patients with pure red cell aplasia

Summary Inhibitory mechanisms of erythropoiesis in 20 patients with pure red cell aplasia (PRCA) were investigated using the technique of in vitro hematopoiesis and an assay for human parvovirus. Complement-dependent serum inhibitors against late erythroid progenitors (CFU-E) were demonstrated in seven of 19 patients examined, and complement-dependent inhibitors against early erythroid progenitors (BFU-E) were demonstrated in three of these seven patients. Nonspecific and complement-independent inhibitors against CFU-E were thought to be associated with the etiology of PRCA in one patient. Human parvovirus-mediated erythropoietic suppression was demonstrated in a patient with complete remission of acute lymphoblastic leukemia complicated with marrow erythroid aplasia, whose serum showed a perfect inhibition against erythroid progenitor cells. T-cell-mediated erythroid suppression was not demonstrated in the patients examined. These findings reveal that erythroid aplasia is associated with complement-dependent serum erythropoietic inhibitor in some patients (36.8% in the present study) with PRCA, but it is difficult to identify the mechanism of erythroid aplasia in more than half of the patients with PRCA. In addition, our present study discovered the presence of parvovirus-mediated marrow pure red cell aplasia in one adult patient with acute lymphoblastic leukemia.     

Pure red cell aplasia associated with expansion of CD3+ CD8+ granular lymphocytes expressing cytotoxicity against HLA-E+ cells

T-cell granular lymphocyte-proliferative disorder (T-GLPD) is characterized by the proliferation of cytotoxic T lymphocytes, and is often associated with pure red cell aplasia (PRCA). The mechanism involved in the development of PRCA in T-GLPD is unknown. Peripheral blood mononuclear cells were isolated from 20 patients with T-GLPD. Ten patients had associated PRCA. Granular lymphocytes (GLs) of T-GLPD are positive for CD94, but not NKG2A. To clarify the functional role of CD94 in T-GLPD, we performed a cytotoxicity assay against the trophoblast cell line, BeWo, which is known to express human leucocyte antigen (HLA)-E, a natural ligand of CD94, and is deficient in other HLA class I and class II antigens. GLs isolated from T-GLPD with PRCA patients killed BeWo cells more significantly than GLs from T-GLPD without PRCA patients. Furthermore, GLs from T-GLPD with PRCA were significantly stimulated by a monoclonal antibody against CD94, whereas those of T-GLPD without PRCA were not. Taken together, HLA-E, a ligand of CD94, was suggested to stimulate CD94+ cells to kill HLA-E+ cells in T-GLPD with PRCA. GLs of T-GLPD with PRCA have a potential positive activity against HLA-E+ cells, whereas GLs from T-GLPD without PRCA do not. CD94 may play a key role in the pathogenesis of PRCA in T-GLPD.     

Pure red cell aplasia: response to therapy with anti-thymocyte globulin

Pure red cell aplasia (PRCA) results from the failure of erythrocyte differentiation and may respond to immunosuppressive therapies. We have treated nine patients with PRCA refractory to steroids and/or cyclophosphamide with anti-thymocyte globulin (ATG). Six patients had normal numbers of erythroid bursts (from erythroid burst-forming units) or erythroid colonies (from erythroid colony-forming units) detectable in vitro, and all responded to therapy with ATG. In vitro studies suggested T-cell inhibition of erythropoiesis in four of these six patients and humorally mediated erythroid suppression in one. In three individuals, virtually no erythroid progenitors were detected in marrow culture. None of these patients responded to ATG. Myelofibrosis, 5q- chromosomal abnormality, or the subsequent development of thrombocytopenia in these individuals suggested that PRCA resulted from an intrinsic stem cell disorder. Our studies demonstrate that ATG is effective therapy for PRCA, and it may be especially useful in children or other patients in whom alkylating agents are not appropriate. We also confirm that erythroid growth in marrow culture predicts those patients who will respond to ATG or other immunosuppressive therapies.     

High expression of the ILT2 (LIR-1) inhibitory receptor for major histocompatibility complex class I molecules on clonal expansions of T large granular lymphocytes in asymptomatic patients.

BACKGROUND AND OBJECTIVES. The lymphoproliferative disorders of large granular lymphocytes (LGLD) are divided into two groups: T-cell type and NK-cell type. These entities may be either asymptomatic or associated with autoimmune manifestations (especially cytopenias). A number of surface receptors, expressed by NK-cells and some T-lymphocyte subsets repress cytotoxicity and cytokine production upon ligation with HLA class I molecules and are clonally expressed in theses lymphoproliferative disorders. These cytotoxic lymphocytes can lyse erythroid progenitors in vitro, and the physiologic lower levels of HLA class I antigens on the erythroid lineage may contribute to this form of autoimmunity. It is conceivable that the clinical outcome of T-LGLD might be influenced by the expression of MHC class I inhibitory receptors. DESIGN AND METHODS. We analyzed the surface expression of these molecules, lectin-like heterodimers (CD94/NKG2A) or killer immunoglobulin (Ig)-like receptors (KIR) and another Ig-like inhibitory receptor, termed ILT2 or LIR-1 in CD8+ cells from 12 cases of ab T-LGLD using specific monoclonal antibodies. RESULTS. None of the LGLD cases had anemia and 11 of 12 patients remain asymptomatic. KIR and CD94/NKG2A expression was detected on CD8+ populations only in some cases of T-LGLD. By contrast, our observations revealed that ILT2 expression was markedly higher in CD8+ cells from LGLD patients than from healthy donors. INTERPRETATION AND CONCLUSIONS. Expression of the ILT2 inhibitory receptor for HLA class I molecules on LGLD cells might indeed contribute to preventing their autoreactivity. Further studies are required to evaluate the expression/function of the ILT2 receptor in patients who eventually become symptomatic. The development of cytopenias in LGLD patients must involve other self-reactive activating receptors. Analysis of the expression and function of triggering NKR in LGLD needs to be carefully addressed.     

Long-term proliferation in vitro of hematopoietic progenitor cells from children with congenital bone marrow failure: effect of rhGM-CSF and rhEPO

We have characterized the proliferation kinetics of hematopoietic cells in long-term marrow cultures (LTMC) from five normal children and seven children with congenital bone marrow failure (four with Fanconi anemia [FA] and three with congenital pure red cell aplasia [PRCA]). Total nonadherent and adherent cells, as well as nonadherent progenitors, were determined weekly in the presence or in the absence of rhGM-CSF (10 ng/ml) or rhEPO (3 U/ml). As compared to normal LTMC, hematopoiesis was drastically reduced in cultures from FA patients. Myeloid and erythroid progenitor cells reached undetectable levels after only 3 and 1 weeks of culture, respectively. This was observed even in cultures supplemented with rhGM-CSF, in which no response to this cytokine occurred. In LTMC from PRCA children, the growth of erythroid and multipotent progenitors was also drastically reduced. Myelopoiesis, on the other hand, showed normal levels during the first three weeks of culture; however, from week 4, there was a significant decrease in the levels of both progenitor and mature cells, reaching undetectable levels several weeks before normal cells did. Response to rhGM-CSF and rhEPO was transient and deficient. Our results suggest that in FA, alterations at the level of primitive progenitor cells are so severe that myeloid, erythroid and multipotent progenitors are unable to proliferate in LTMC, even in the presence of rhGM-CSF. In patients with PRCA the erythroid arm of hematopoiesis is preferentially affected and addition of rhGM-CSF and/or rhEPO to these cultures had little or no effect on erythroid cell production. Interestingly, myelopoiesis in this culture system was deficient as well and response to rhGM-CSF was defective, suggesting that the myeloid lineage is also altered in congenital PRCA.     

Successful treatment of chronic refractory pure red cell aplasia with antithymocyte globulin: correlation with in vitro erythroid culture studies

Two contrasting cases of chronic refractory pure red cell aplasia (PRCA) responsive to a commercial preparation of horse antihuman thymocyte globulin (ATG) are reported. Both cases were refractory to trials of cyclophosphamide, corticosteroids, and plasmapheresis. One patient developed a reticulocytosis after a single intravenous infusion of ATG; the other patient responded after administration of 14.7 g of ATG over a 28-day course. At presentation, erythroid progenitors (CFU-E and BFU-E) in one patient were normal; in the second patient, the number of erythroid progenitors was severely reduced. Neither patient had a serum IgG inhibitor to progenitor cells as judged by in vitro erythroid colony studies. Both patients had increased numbers of marrow T-cells and co-culture studies in one case were consistent with T-cell-mediated suppression of erythropoiesis. These studies confirm that ATG is a useful agent in the treatment of refractory PRCA. However, ATG may not act by removal of T suppressor cells in all cases.     

Characterization of hepatic progenitors from human fetal liver during second trimester

AIM： To enrich hepatic progenitors using epithelial cell adhesion molecule （EpCAM） as a marker from human fetal liver and investigate the expression of human leukocyte antigen （HLA） and their markers associated with hepatic progenitor cells.
METHODS： EpCAM ＋ve cells were isolated using magnetic cell sorting （MACS） from human fetuses （n = 10） at 15-25 wk gestation. Expression of markers for hepatic progenitors such as albumin, alpha-fetoprotein （AFP）, CD29 （integrin ~1）, CD49f （integrin c~6） and CD90 （Thy 1） was studied by using flow cytometry, immunocytochemistry and RT-PCR; HLA class Ⅰ （A, B, C） and class Ⅱ （DR） expression was studied by flow cytometry only. RESULTS： FACS analysis indicated that EpCAM ＋ve cells were positive for CD29, CD49f, CD90, CD34, HLA class I, albumin and AFP but negative for HLA class Ⅱ （DR） and CD45. RT PCR showed that EpCAM ＋ve cells expressed liver epithelial markers （CK18）, biliary specific marker （CK19） and hepatic markers （albumin, AFP）. On immunocytochemical staining, EpCAM ＋ve cells were shown positive signals for CK18 and albumin.
CONCLUSION： Our study suggests that these EpCAM ＋ve cells can be used as hepatic progenitors for cell transplantation with a minimum risk of alloreactivity and these cells may serve as a potential source for enrichment of hepatic progenitor.     

Cyclosporin-a for the treatment of pure red cell aplasia in a patient with chronic lymphocytic leukemia

A 62-year-old man with B-cell chronic lymphocytic leukemia had three separate episodes of pure red cell aplasia (PRCA). The last episode was treated with cyclosporin-A (CyA) and prednisone. After the patient was on the therapy for 2 weeks, erythropoietic recovery was observed and with continued therapy the hematocrit (Hct) became normal. The PRCA remission was associated with a fall in the blood lymphocyte count, and a reduction in the spleen and lymph node size and bone marrow lymphocyte density. At diagnosis of PRCA the blood T-cells bearing IgG Fc receptors (T gamma cells) were increased, and the marrow contained very few or no late-stage erythroid progenitors. After remission of PRCA the T gamma cell fraction decreased, and the marrow erythroid progenitor's number became normal. We speculate that therapy with CyA and prednisone inhibited the production of interleukins-1 and -2 from monocytes and T-cells, respectively, and was responsible for the reduction of the T gamma cell fraction and B-cell leukemic mass in this patient. Further, we believe that normalization of T gamma cells in association with the therapy was responsible for the PRCA remission.     

Pure red cell aplasia complicating the course of long-standing mantle cell lymphoma

Pure red cell aplasia (PRCA) is a rare cause of severe hypoplastic anemia characterized by profound depletion of erythroid precursors. Although PRCA may be associated with lymphoproliferative diseases, it has never been described in mantle cell lymphoma (MCL). We report what to our knowledge is the first case of a patient with indolent, non-nodal MCL complicated by PRCA. The patient presented with severe hypoproliferative anemia in the setting of a long-standing diagnosis of B-cell chronic lymphocytic leukemia. Bone marrow studies revealed the complete absence of erythroid progenitors. Cyclin D1 positivity on immunohistochemistry, confirmed by a positive FISH for t(11;14) (q13;q32), established the final diagnosis of MCL in conjunction with PRCA. Rituximab monotherapy led to rapid remission of splenomegaly and the leukemic picture, but the patient achieved transfusion independency only with subsequent administration of cyclosporine-A, and remained so during the subsequent 15 months despite the gradual disease recurrence.     

Pure red cell aplasia: lymphocyte inhibition of erythropoiesis

The pathogenesis of pure red cell aplasia (PRCA) was studied in a patient who had no evidence of malignancy. In marrow culture, no erythroid colonies (from late erythroid progenitors [CFU-E]) but normal numbers of well-haemoglobinized erythroid bursts (from early erythroid progenitors [BFU-E]) were found, indicating that BFU-E existed in the patient but that their subsequent in vivo differentiation was inhibited. Autologous coculture studies suggested that inhibition was mediated by the patient's ER+ lymphocytes. After remission was induced with cyclophosphamide, autologous ER + cells no longer suppressed in vitro erythropoiesis. However, cryopreserved ER + cells, obtained with anaemia, suppressed BFU-E growth from remission marrow. An expanded population of large granular lymphocytes (LGL) with ER +, F_cγ+. T3 +, T8 +, HNK-1 +, Ia —, M1 — phenotype and no functional natural killer (NK) cell activity was noted during PRCA that reverted to normal with remission. For this patient, both in vivo and in vitro evidence demonstrates a cellular inhibition of erythropoiesis at the level of differentiation between BFU-E and CFU-E.     

Treatment of refractory pure red cell aplasia with cyclosporine A: disappearance of IgG inhibitor associated with clinical response

Remissions were obtained in 6/9 evaluable patients with pure red cell asplasia (PRCA) refractory to other immunosuppressive agents who were treated with cyclosporine A (CsA). Four of these patients have remained in continuous remission off all treatment for 4-19 months. Another patient who stopped CsA abruptly relapsed, but responded to reinstitution of therapy. The sixth patient died of a cerebrovascular accident while in remission on a low dose of CsA. Acute side effects were minimal and were responsive to dose reduction. One patient developed a lymphoma while in an unmaintained remission, and one patient who did not respond to CsA was found to have a lymphoma approximately a year after stopping treatment. In vitro studies of autologous erythroid progenitors in a patient with an IgG inhibitor of erythropoiesis showed a reduction of autoantibody associated with the response to CsA. The antigen to which this inhibitor is directed was expressed only during the marrow erythroid burst-forming unit (BFU-E) period of erythroid differentiation. CsA can induce sustained remissions in cases of PRCA refractory to other multiple agents, and these remissions may be associated with a reduction in autoantibody to erythroid progenitor cells. Further studies of patients with PRCA who respond to CsA may lead to an improved understanding of this disorder.     

Successful treatment of pure red cell aplasia with a single dose of rituximab in a child after major ABO incompatible peripheral blood allogeneic stem cell transplantation for acquired aplastic anemia

Pure red cell aplasia (PRCA) is a well-known although infrequent hematologic complication after allogeneic bone marrow transplantation. PRCA occurs in cases of major ABO-mismatch between donor and recipient and is believed to be due to inhibition of donor erythroid progenitors by residual host isohemagglutinins. We report a 10-year-old boy with post-hepatitis aplastic anemia (AA) who developed PRCA after HLA-matched familial peripheral blood stem cell transplantation (SCT) following conditioning with Cph 200 mg/kg + ATG 90 mg/kg. Granulocyte engraftment occurred on day +18, platelet engrafted on day +40, while reticulocytopenia at 0% persisted until day +118, and erythroid precursors were totally absent from bone marrow. After a single dose of rituximab 200 mg/m(2)administered on day +118 PRCA resolved and on day +132 the reticulocytes rose to 5.7%. On day +139 the Hb reached 137 g/l and the erythroid lineage in BM increased to 21%. We conclude that due to the rapid recovery from PRCA and lack of side effects, rituximab should be tried as first-line treatment of PRCA after allo-SCT.     

Mesenchymal stem cells for the treatment of refractory pure red cell aplasia after major ABO-incompatible hematopoietic stem cell transplantation

Pure red cell aplasia (PRCA) is a well-known, although infrequent, hematological complication after allogeneic hematopoietic stem cell transplantation (HSCT). PRCA occurs in cases of major ABO mismatch between donor and recipient and is believed to be due to inhibition of donor erythroid progenitors by residual host isohemagglutinins. The purpose of our study was to further evaluate the efficacy of human adipose tissue-derived mesenchymal stem cells (AMSC) as the salvage therapy for refractory PRCA after major ABO-incompatible HSCT. Two patients with refractory pure red cell aplasia received intravenous infusions of AMSC at a dose of 1.5 × 10⁶/kg of the patients’ weight, and rapid recovery from PRCA without any side effects was observed. We conclude that AMSC seems to be a promising therapeutic option in patients with PRCA after ABO-mismatched HSCT, in whom conventional treatment fails.     

Pure red cell aplasia induced by B19 parvovirus during allogeneic bone marrow transplantation

We report a patient who had abrupt onset of pure red cell aplasia (PRCA) induced by B19 parvovirus during allogeneic bone marrow transplantation (BMT). A 14-year-old girl with APL in complete remission was admitted in February 1988, for the purpose of BMT. She was received marrow from HLA identical sister on March 17, 1988 (day 0). She received 120 mg/kg cyclophosphamide and 12 Gy total body irradiation for conditioning of BMT. For graft-versus-host disease (GVHD) prophylaxis she was given cyclosporine and short term methotrexate. She did not develop acute GVHD after BMT, but on the day 28 a bone-marrow aspirate revealed findings of PRCA. During this course the number of white blood cell and platelet favorably recovered. B 19 parvovirus DNA was detected in the serum of the day 30 and day 42. Antihuman B 19 parvovirus (HPV) antibody titers were increased: the values of anti-HPV IgM were suddenly elevated and those of anti-HPV IgG were elevated. Serum on the day 42 inhibited erythroid progenitors (CFU-E, BFU-E) but not inhibited myeloid progenitors (CFU-C). A reticulocyte count recovered on the day 50. As the patient was HPV-IgG negative prior to BMT and the donor was HPV-IgG seronegative, the source of infection may be platelet transfusion (day 7 through 14).     

Carbonic anhydrase I is an early specific marker of normal human erythroid differentiation

The expression of carbonic anhydrase (CA) as a marker of erythroid differentiation was investigated by immunologic and enzymatic procedures. A polyclonal anti-CA antibody was obtained by immunizing rabbits with purified CA I isozyme. This antibody is reactive with CA I but not with CA II. Within blood cells, CA I was only present in erythrocytes, whereas CA II was also detected in platelet lysates by enzymatic assay. Concerning marrow cells, identifiable erythroblasts and some blast cells expressed CA I. Most of the glycophorin A-positive marrow cells were clearly labeled by the anti-CA I antibody. However, rare CA I-positive cells were not reactive with anti-glycophorin A antibodies. We therefore investigated whether these cells were erythroid precursors or progenitors. In cell sorting experiments of marrow cells with the FA6 152 monoclonal antibody, which among hematopoietic progenitors is reactive only with CFU-E and a part of BFU- E, was performed, CA I+ cells were found mainly in the positive fraction. The percentage of CA I+ cells nonreactive with anti- glycophorin A antibodies contained in the two fractions was in the same range as the percentage of erythroid progenitors identified by their capacity to form colonies. In addition, the anti-CA I antibody labeled blood BFU-E-derived colonies as early as day 6 of culture, whereas in similar experiments with the anti-glycophorin A antibodies, they were stained three or four days later. No labeling was observed in CFU-GM- or CFU-MK-derived colonies. The phenotype of the day 6 cells expressing CA I was similar to that of erythroid progenitors (CFU-E or BFU-E): negative for glycophorin A and hemoglobin, and positive for HLA-DR antigen, the antigen identified by FA6 152, and blood group A antigen. Among the cell lines tested, only HEL cells expressed CA I, while K562 was unlabeled by the anti-CA I antibody. In contrast, HEL and K562 cells expressed CA II as detected by a biochemical technique. Synthesis of CA I, as with other erythroid markers such as glycophorin A and hemoglobin, was almost abolished after 12-O-tetradecanoyl-phorbol-13 acetate treatment of HEL cells. In conclusion, CA I appears to be an early specific marker of the erythroid differentiation, expressed by a cell with a similar phenotype as an erythroid progenitor.     

Somatic mutations in acquired pure red cell aplasia

Acquired pure red cell aplasia (PRCA) is a syndrome characterized by anemia and a marked reduction of erythroid progenitor cells with various etiologies. The 3 major subtypes of PRCA are idiopathic PRCA, large granular lymphocytic leukemia-associated PRCA and thymoma-associated PRCA, which are thought to be caused by a T-cell-mediated mechanism. In these 3 subtypes, an expansion of clonal cytotoxic T cells is often detected. In addition, those T cells recurrently harbor somatic mutations of STAT3, a gene coding one of the important signal transducers in the JAK/STAT system. Somatic mutations of clonal hematopoiesis (CH)-related genes, including epigenetic modifying genes, have also been reported, however, the data are still not mature enough upon which to draw conclusion, Somatic mutations of STAT3 and CH-related genes may be unique characteristics of acquired PRCA. However, their involvement in dyserythropoiesis or clinical relevance to the clinical course of those somatic mutations. Mutational landscapes, their involvements in dyserythropoiesis and clinical relevance in acquired PRCA remains unclear, and further investigation is needed.     

Low-molecular-weight protein (LMP)2/LMP7 abnormality underlies the downregulation of human leukocyte antigen class I antigen in a hepatocellular carcinoma cell line

BACKGROUND: Tumor cells may alter the expression of numerous components involved in antigen-processing machinery to decrease human leukocyte antigen (HLA) class I expression, allowing the tumor cells to escape immune surveillance. The purpose of the present study was to investigate the involvement of these components in the downregulation of HLA class I expression in human hepatocellular carcinoma cell line BEL7,404. METHODS: Expression of HLA-I and antigen presentation-related genes were analyzed by flow cytometry and polymerase chain reaction. The HLA class I-deficient BEL7,404 cell was transfected with the low-molecular-weight protein (LMP) 2 and LMP7 gene and were analyzed by flow cytometry for restoration of surface HLA class I expression. RESULTS: The BEL7,404 cells downregulated the expression of HLA class I antigen and lacked expression of LMP2 and LMP7. Interferon (IFN)-gamma treatment increased the expression of LMP2 but not LMP7. The LMP2-transfected BEL7,404 cells or LMP2 and LMP7-cotransfected cells restored surface HLA class I expression while LMP7-transfected cells did not. However, in IFN-gamma-treated BEL7,404 cells, transfection with the LMP7 gene induced more HLA class I expression than mock transfection. CONCLUSIONS: The LMP2 gene was required for the expression of HLA class I molecules in BEL7,404. The LMP7 was not the major reason for loss of HLA class I in BEL7,404 cells, although the supply of exogenous LMP7 could increase surface expression of HLA class I antigen.     

Stochastic expression of fetal hemoglobin in adult erythroid cells.

The expression of fetal hemoglobin, Hb F, in the adult cells is cellularly restricted both in vivo and in culture. Because, in cultures of erythroid progenitors, subclones that express or fail to express Hb F are derived from the same erythroid stem cell, a mechanism must exist whereby Hb F expression segregates in the progeny of erythroid progenitors during their differentiation. We present mathematical analyses of experimental data which suggest that expression of Hb F in human adult erythroid cells occurs on a stochastic basis. We quantified Hb F expression among the subclones of erythroid bursts (clones) in vitro by labeling subclones with fluorescent anti-Hb F antibodies. The observed data were compared with predictions from a stochastic model with the assumption that the expression of Hb F in a subclone occurs with a probability P equal to the frequency of Hb F-expressing subclones in an experiment. There was good fit between the observed and predicted data with respect to: (i) the relative frequencies of monomorphic F+, monomorphic F-, and bimorphic F+/F- bursts, respectively; (ii) the size distributions among F+, F- and F+/F- bursts; and (iii) the proportions of subclones expressing Hb F within bimorphic F+/F- bursts. Given the hypothesis that erythroid progenitors which have an active Hb F program are less differentiated than cells which do not proceed to express Hb F, the stochastic event indicated by our analyses may be the probability that adult erythroid progenitor cells undergo terminal differentiation at an earlier stage than usual.     

Enhancement of growth and survival and alterations in Bcl-family proteins in beta-thalassemic erythroid progenitors by novel short-chain fatty acid derivatives

Accelerated apoptosis of erythroid progenitors is a characteristic of beta-thalassemia which presents a significant barrier to definitive therapeutic approaches utilizing induction of endogenous fetal globin gene expression. gamma-globin gene expression may not be inducible in, or may not be able to rescue, erythroid cells in which programmed cell death is initiated early in erythroblast development. In this report, short-chain fatty acid derivatives (SCFADs) which induce fetal globin gene expression were tested for their ability to promote proliferation and survival of erythroid progenitors cultured from beta-thalassemic subjects, and of cytokine-dependent erythroid cell lines. Certain SCFADs promoted thalassemic Bfu-e growth and cytokine-independent growth and survival of erythroid cell lines. A 40-80% increase in erythroid Bfu-e colony number was observed in cultures established with any of five mitogenic SCFADs, compared to control or butyrate-treated cultures from the same subjects. Immunoblot analysis demonstrated that these same SCFADs also regulated the expression of specific protein inhibitors of apoptosis. Anti-apoptotic ratios of the proteins Bcl-xL/Bcl-xS in thalassemic Bfu-e were increased by 30-120% with exposure to the SCFDs, compared to the ratios in the same cells cultured under control conditions. Similar anti-apoptotic increases in Mcl-1L/Mcl-1S ratios were induced by the SCFADs. These findings suggest that select fetal globin-inducing SCFADs which enhance proliferation of beta-thalassemia progenitors may enhance survival of these progenitors by altering levels of Bcl-family protein members. This combination of effects should enhance erythroid cell survival in the beta-thalassemia syndromes, allowing fetal globin gene expression to be induced more effectively than currently available, growth-suppressing, fetal globin-inducing agents, such as the butyrates or chemotherapeutic agents.