Gene mutation profile in patients with acquired pure red cell aplasia.

Acquired pure red cell aplasia (PRCA) is a disorder characterized by normocytic anemia associated with reticulocytopenia and an absence of erythroblasts. The gene mutation profile in acquired PRCA is not defined yet. In this study, we aimed to identify the gene mutation spectrum of patients with acquired PRCA and the correlation between gene mutations and response to immunosuppressive therapy (IST). Thirty newly diagnosed acquired PRCA patients were enrolled in this study, and then whole-exome sequencing were performed among these patients and a panel with 93 candidate genes which associated with other bone marrow failure for the following analysis. Subsequently patients were treated with IST for at least 2 years. When treated with IST, there were thirteen complete response, ten partial response (ORR 76.7%), and seven no response at a medium of 8 (6-10) months. Totally twenty-three mutations in fifteen genes were detected in sixteen patients (53%). The mutated genes were associated with transcription, signal transduction, and epigenetic regulation pathways. The most frequent transitions in the point mutations were C > T. Age, gender, hemoglobin level at diagnosis, and gene mutation or not did not influence the response to IST. However, although patients with BCOR or BCORL1 mutations had a similar response to IST compared with those without mutation (P = 0.235), they had a better response than those with other gene mutations (P = 0.0193). In conclusion, patients with acquired PRCA may have clonal gene mutations. The patients with BCOR and BCORL1 mutations may suggest a better response to IST compared with those with other mutations.

Acquired Pure Red Cell Aplasia and Acquired Amegakaryocytic Thrombocytopenia Associated With Clonal Expansion of T-Cell Large Granular Lymphocytes in a Patient With Lipopolysaccharide-responsive Beige-like Anchor (LRBA) Protein Deficiency.

Acquired pure red cell aplasia and acquired amegakaryocytic thrombocytopenic purpura are rare in children. Similarly, clonal expansion of T-cell large granular lymphocytes is infrequently seen in pediatrics. Lipopolysaccharide-responsive beige-like anchor (LRBA) protein deficiency is a recently described immunodeficiency syndrome that has been associated with inflammatory bowel disease and autoimmune phenomena such as Evans syndrome. Here, we describe a patient with LRBA deficiency who developed acquired pure red cell aplasia and acquired amegakaryocytic thrombocytopenic purpura associated with expansion of clonal T-cell large granular lymphocytes. This has not been described in the literature previously and adds to the knowledge on the spectrum of manifestations of LRBA deficiency.

Activated Gs signaling in osteoblastic cells alters the hematopoietic stem cell niche in mice.

Adult hematopoiesis occurs primarily in the BM space where hematopoietic cells interact with stromal niche cells. Despite this close association, little is known about the specific roles of osteoblastic lineage cells (OBCs) in maintaining hematopoietic stem cells (HSCs), and how conditions affecting bone formation influence HSC function. Here we use a transgenic mouse model with the ColI(2.3) promoter driving a ligand-independent, constitutively active 5HT4 serotonin receptor (Rs1) to address how the massive increase in trabecular bone formation resulting from increased G(s) signaling in OBCs impacts HSC function and blood production. Rs1 mice display fibrous dysplasia, BM aplasia, progressive loss of HSC numbers, and impaired megakaryocyte/erythrocyte development with defective recovery after hematopoietic injury. These hematopoietic defects develop without compensatory extramedullary hematopoiesis, and the loss of HSCs occurs despite a paradoxical expansion of stromal niche cells with putative HSC-supportive activity (ie, endothelial, mesenchymal, and osteoblastic cells). However, Rs1-expressing OBCs show decreased expression of key HSC-supportive factors and impaired ability to maintain HSCs. Our findings indicate that long-term activation of G(s) signaling in OBCs leads to contextual changes in the BM niche that adversely affect HSC maintenance and blood homeostasis.

Allogeneic Th1 cells home to host bone marrow and spleen and mediate IFNγ-dependent aplasia.

Bone marrow graft failure and poor graft function are frequent complications after hematopoietic stem cell transplantation and result in significant morbidity and mortality. Both conditions are associated with graft-versus-host disease (GVHD), although the mechanism remains undefined. Here we show, in 2 distinct murine models of GVHD (complete MHC- and class II-disparate) that mimic human peripheral blood stem cell transplantation, that Th1 CD4(+) cells induce bone marrow failure in allogeneic recipients. Bone marrow failure after transplantation of allogeneic naïve CD4(+) T cells was associated with increased CD4(+) Th1 cell development within bone marrow and lymphoid tissues. Using IFNγ-reporter mice, we found that Th1 cells generated during GVHD induced bone marrow failure after transfers into secondary recipients. Homing studies demonstrated that transferred Th1 cells express CXCR4, which was associated with accumulation within bone marrow and spleen. Allogeneic Th1 cells were activated by radiation-resistant host bone marrow cells and induced bone marrow failure through an IFNγ-dependent mechanism. Thus, allogeneic Th1 CD4(+) cells generated during GVHD traffic to hematopoietic sites and induce bone marrow failure via IFNγ-mediated toxicity. These results have important implications for prevention and treatment of bone marrow graft failure after hematopoietic stem cell transplantation.

Frequent STAT3 mutations in CD8+ T cells from patients with pure red cell aplasia.

Dysregulation of T-cell-mediated immunity is responsible for acquired pure red cell aplasia (PRCA). Although STAT3 mutations are frequently detected in patients with T-cell large granular lymphocytic leukemia (T-LGLL), which is often complicated by PRCA and which is also reported to be associated with acquired aplastic anemia (AA) and myelodysplastic syndrome (MDS), whether STAT3-mutated T cells are involved in the pathophysiology of PRCA and other types of bone marrow failure remains unknown. We performed STAT3 mutation analyses of the peripheral blood mononuclear cells from PRCA patients (n = 42), AA (n = 54), AA-paroxysmal nocturnal hemoglobinuria (AA-PNH; n = 7), and MDS (n = 21) using an allele-specific polymerase chain reaction and amplicon sequencing. STAT3 mutations were not detected in any of the 82 patients with AA/PNH/MDS but were detected in 43% of the 42 PRCA patients. In all 7 STAT3-mutation-positive patients who were studied, the STAT3 mutations were restricted to sorted CD8+ T cells. The prevalence of STAT3 mutation in idiopathic, thymoma-associated, autoimmune disorder-associated, and T-LGLL-associated PRCA was 33% (5 of 15), 29% (2 of 7), 20% (1 of 5), and 77% (10 of 13), respectively. The STAT3-mutation-positive patients were younger (median age, 63 vs 73 years; P= .026) and less responsive to cyclosporine (46% [6 of 13] vs 100% [8 of 8]; P= .0092) in comparison with STAT3-mutation-negative patients. The data suggest that STAT3-mutated CD8+ T cells may be closely involved in the selective inhibition of erythroid progenitors in PRCA patients.

Radiation-induced increase in plasma Flt3 ligand concentration in mice: evidence for the implication of several cell types.

Circulating T lymphocytes were proposed as the main producer of Flt3 ligand. However, during aplasia, there is a drastic reduction in the number of T lymphocytes, while plasma Flt3 ligand concentration is increased. This contradiction prompted us to compare variations in plasma Flt3 ligand during radiation-induced aplasia in BALB/c mice and in T-lymphocyte-deficient NOD-SCID mice to delineate the role of T lymphocytes in the increase in Flt3 ligand concentration. The results showed that plasma Flt3 ligand concentration was increased similarly in the two strains of mice, and that Flt3 ligand concentration was negatively correlated to the number of residual hematopoietic progenitors. Moreover, the Flt3 ligand mRNA expression and Flt3 ligand protein concentration were similar in the two strains of mice in all organs tested, i.e. thymus, spleen, bone marrow, liver, brain and blood cells. These results confirm that Flt3 ligand concentration in the blood is a reflection of bone marrow function and that T lymphocytes are not the main regulator of Flt3 ligand variations during aplasia.

Increased expression of c-maf in pure red cell aplasia secondary to plasma cell dyscrasia.

Th2 dominancy in the peripheral T helper (Th) cell subsets were reported to be involved in the pathogenesis of pure red cell aplasia (PRCA). We encountered a PRCA case secondary to plasma cell dyscrasia that showed Th2 dominancy at the relapse of PRCA. Increased expression of c-maf, a transcriptional factor which induces Th2 differentiation of naive T-cells, and elevated expression of interleukin (IL)-4 were observed in the RNA derived from patient's bone marrow at relapse of PRCA. Following the administration of methylprednisolone which improved PRCA, normalization of Th1/Th2 ratio and decreased expression of c-maf and IL-4 were observed, which suggests that the upregulation of c-maf might have played a role in the pathogenesis of PRCA secondary to plasma cell dyscrasia.

CDR3-independent expansion of Vδ1 T lymphocytes in acquired chronic pure red cell aplasia.

Although there exist case reports describing the association of clonal expansion of γδ T cells with chronic acquired pure red cell aplasia (PRCA), there is no consensus regarding whether clonal expansion of γδ T cells are generally found in chronic PRCA. We examined the γδ T cell receptor repertoire in 19 PRCA patients and found that there was a difference in γδ T-cell repertoires between PRCA patients and healthy donors. We observed an increase in Vδ1 γδ T cells and a decrease in Vδ2 T cells in PRCA patients. CDR3δ1 size distribution patterns were skewed in 9 out of 13 PRCA patients examined, although the skewing was also observed in 7 out of 10 healthy individuals. No significant changes were present in CDR3δ1 size distribution between PRCA patients and healthy donors. Moreover, no apparent consensus amino acid motifs were identified in PRCA patients. Expansion of Vδ1 T cells and depletion of Vδ2 T cells are unique features for chronic acquired PRCA but expansion of Vδ1 T cells does not seem to be the consequence of CDR3-dependent selection. We conclude that clonal expansion of Vδ1 T cells is not a general feature for chronic acquired PRCA.

Burst-forming unit-erythroid assays to distinguish cellular bone marrow failure disorders.

Patients with cytopenias and a cellular bone marrow can be a diagnostic and therapeutic challenge. Previous reports suggested a role for progenitor assays for diagnosis and predicting response to therapy. We report the results of Burst-forming unit-erythroid (BFU-E) assays in 48 consultative cases of single or multilineage cytopenias with cellular marrows. The final diagnoses included 17 patients with myelodysplastic syndrome, 9 patients with pure red cell aplasia (non-large granular lymphocytosis [LGL] in etiology], 15 patients with LGL (eight of whom had a single-lineage cytopenia only, whereas the other seven had multilineage cytopenias), and 7 patients with cytopenias associated with systemic inflammation from autoimmune conditions. In this cohort, nonmalignant diseases were well-distinguished from myelodysplastic syndrome by BFU-E growth. Our data suggest that low BFU-E growth (less than 10 BFU-E per 10(5) marrow mononuclear cells) helps to exclude LGL, pure red cell aplasia, or cytopenias associated with systemic inflammation as a cause of pancytopenia with a sensitivity of 96.8%, specificity of 76.5%, and a predictive value of 88.2% (p = 0.0001). BFU-E growth also was examined to predict treatment response. Of the 29 patients in this cohort treated with immunosuppressive therapy, there was an 86% response rate with 25 responders (11 partial responses and 14 complete responses) and 4 nonresponders. This result correlated with higher BFU-E growth. Our results suggest that BFU-E assays are a useful adjunct in the diagnosis and management of cytopenias in the setting of a normocellular or hypercellular marrows.

Strategy to confirm the presence of anti-erythropoietin neutralizing antibodies in human serum.

Functional cell-based assays are the preferred method to test for the presence of anti-rHuEPO neutralizing antibodies (NAbs). However, due to the unpredictable nature of test serum matrix effects on cell-based assays, confirmatory assays are essential for verifying NAb positive results observed during the course of sample testing. The cell-based assay used for the detection of NAbs described by Wei et al. [1] used 32D-EPOR cells, a murine myeloid cell line transfected with the human EPO receptor (EPOR). The 32D-EPOR cell line responded to either rHuEPO or murine interleukin 3 (mIL-3) with proliferation. NAbs were expected to only inhibit rHuEPO-induced cell proliferation and not mIL-3 induced proliferation. Due to reliance on proliferation, the results from this cell-based assay can be confounded by the presence of non-antibody inhibitory serum factors. This paper describes a strategy for confirming that the inhibition of rHuEPO-induced proliferation in a cell-based assay is only attributable to NAbs. The strategy of antibody depletion uses a resin mixture composed of Protein G Sepharose and Protein L Sepharose (Protein G/L resin) to significantly reduce the concentration of immunoglobulins of IgG, IgM and IgA isotypes from human serum prior to testing in the cell-based assay. If the reduction in immunoglobulins in a serum sample corresponds to a reduction in inhibition of EPO-induced proliferation, it would infer that EPO neutralizing activity is antibody-mediated and not due to non-antibody inhibitory serum factors.

Pure red cell aplasia associated with Good's syndrome accompanied by decreased stem cell factor production in the bone marrow.

A 79-year-old Japanese woman diagnosed with pure red cell aplasia (PRCA) associated with thymoma and hypogammaglobulinemia (Good's syndrome) was successfully treated with cyclosporine-A after a thymectomy. We further studied the etiology of this case. A burst-forming unit erythroid (BFU-E) assay with SCF restored erythropoiesis in vitro. SCF production was reduced in bone marrow stromal cells; however, it was restored in vitro and in vivo after cyclosporine-A treatment.

Spontaneous IL-2 production in vitro in two patients with pure red cell aplasia.

We investigated spontaneous cytokine production in two patients with pure red cell aplasia (PRCA). The peripheral blood mononuclear cells (PBMNC) from two patients produced IL-2. Cyclosporin A (CyA) suppressed in vitro IL-2 production in one patient, but not in the other. Spontaneous IL-2 production disappeared in one patient 10 months after the start of CyA therapy. The patient for whom CyA therapy was stopped after the disappearance of spontaneous IL-2 production has remained in continuous remission for 1 year. The present case suggests that spontaneous IL-2 production in PBMNC might be an indicator of disease activity.

Model of reticuloendothelial iron metabolism in humans: abnormal behavior in idiopathic hemochromatosis and in inflammation.

Iron transport in the reticuloendothelial (RE) system plays a central role in iron metabolism, but its regulation has not been characterized physiologically in vivo in humans. In particular, why serum iron is elevated and RE cells are much less iron-loaded than parenchymal cells in idiopathic hemochromatosis is not known. The processing of erythrocyte iron by the RE system was studied after intravenous (IV) injection of 59Fe heat-damaged RBCs (HDRBCs) and 55Fe transferrin in normal subjects and in patients with iron deficiency, idiopathic hemochromatosis, inflammation, marrow aplasia, or hyperplastic erythropoiesis. Early release of 59Fe by the RE system was calculated from the plasma iron turnover and the 59Fe plasma reappearance curve. Late release was calculated from the ratio of 59Fe/55Fe RBC utilization in 2 weeks. The partitioning of iron between the early (release from heme catabolism) and late (release from RE stores) phases depended on the size of RE iron stores, as illustrated by the inverse relationship observed between early release and plasma ferritin (P less than .001). There was a strong correlation between early release and the rate of change of serum iron levels during the first three hours in normal subjects (r = .85, P less than .001). Inflammation produced a blockade of the early release phase, whereas in idiopathic hemochromatosis early release was considerably increased as compared with subjects with similar iron stores. Based on these results, we describe a model of RE iron metabolism in humans. We conclude that the RE system appears to determine the diurnal fluctuations in serum iron levels through variations in the immediate output of heme iron. In idiopathic hemochromatosis, a defect of the RE cell in withholding iron freed from hemoglobin could be responsible for the high serum iron levels and low RE iron stores.