Activated T-lymphocytes with myelosuppressive properties in patients with chronic idiopathic neutropenia

Repurposing of rituximab biosimilars to treat B cell mediated autoimmune diseases

Rituximab, the first monoclonal antibody approved for the treatment of lymphoma, eventually became one of the most popular and versatile drugs ever in terms of clinical application and revenue. Since its patent expiration, and consequently, the loss of exclusivity of the original biologic, its repurposing as an off-label drug has increased dramatically, propelled by the development and commercialization of its many biosimilars. Currently, rituximab is prescribed worldwide to treat a vast range of autoimmune diseases mediated by B cells. Here, we present a comprehensive overview of rituximab repurposing in 115 autoimmune diseases across 17 medical specialties, sourced from over 1530 publications. Our work highlights the extent of its off-label use and clinical benefits, underlining the success of rituximab repurposing for both common and orphan immune-related diseases. We discuss the scientific mechanism associated with its clinical efficacy and provide additional indications for which rituximab could be investigated. Our study presents rituximab as a flagship example of drug repurposing owing to its central role in targeting cluster of differentiate 20 positive (CD20) B cells in 115 autoimmune diseases.

How to Make the Right Diagnosis in Neutropenia

Isolated neutropenia without anemia or thrombocytopenia is a common clinical problem. The etiology of neutropenia may vary from transient bone marrow suppression, caused by self-limited viral illnesses, to previously undiagnosed congenital syndromes or serious systemic diseases. Consequently, determining the underlying cause of neutropenia and what treatment is required can be challenging. Acquired neutropenia is common and most of the times an etiologic factor can be found. Congenital neutropenia (CN) is rare, and we still have a lot to learn from mutational analysis as to the exact role of gene abnormalities in the pathogenesis of these complex diseases. This mini-review discusses a proposed approach to neutropenia in the adult patient.

Incidence and Prognosis of Clonal Hematopoiesis in patients with Chronic Idiopathic Neutropenia

The incidence and prognosis of clonal hematopoiesis in patients with isolated neutropenia among patients with idiopathic cytopenia of undetermined significance (ICUS), known as ICUS-N or chronic idiopathic neutropenia (CIN) patients, is poorly defined. In the present study we sought to investigate the frequency and clinical significance of mutations of genes implicated in myeloid malignancies using next generation sequencing, in CIN patients (n=185) with a long follow-up. We found that 21/185 patients (11.35%) carried totally 25 somatic mutations in 6 genes with median variant allele frequency (VAF) 12.75%. The most frequently mutated genes were DNMT3A and TET2 involving more than 80% of patients followed by IDH1/2, SRSF2 and ZRSR2. The frequency of transformation to a myeloid malignancy was low in the total group of patients (5/185 patients; 2.70%). However, from the transformed patients four belonged to the clonal (4/21; 19.05%) and one to the non-clonal (1/164; 0.61%) group, indicating that the presence of mutation(s) confers a relative risk for transformation 31.24 (P = 0.0017). The VAF of the mutant clones in the transformed patients was higher than 10% in all cases and the genes most frequently associated with malignant transformation were the SRSF2 and IDH1. No significant differences were identified between clonal and non-clonal groups in the severity of neutropenia. Patients with clonal disease were older compared to non-clonal patients. These data contribute to the better understanding of the heterogeneous entities underlying ICUS and highlight the importance of the mutation analysis for the diagnosis and prognosis of patients with unexplained neutropenias.

Immunodeficiency and bone marrow failure with mosaic and germline TLR8 gain of function

Inborn errors of immunity (IEI) are a genetically heterogeneous group of disorders with a broad clinical spectrum. Identification of molecular and functional bases of these disorders is important for diagnosis, treatment, and an understanding of the human immune response. We identified 6 unrelated males with neutropenia, infections, lymphoproliferation, humoral immune defects, and in some cases bone marrow failure associated with 3 different variants in the X-linked gene TLR8, encoding the endosomal Toll-like receptor 8 (TLR8). Interestingly, 5 patients had somatic variants in TLR8 with <30% mosaicism, suggesting a dominant mechanism responsible for the clinical phenotype. Mosaicism was also detected in skin-derived fibroblasts in 3 patients, demonstrating that mutations were not limited to the hematopoietic compartment. All patients had refractory chronic neutropenia, and 3 patients underwent allogeneic hematopoietic cell transplantation. All variants conferred gain of function to TLR8 protein, and immune phenotyping demonstrated a proinflammatory phenotype with activated T cells and elevated serum cytokines associated with impaired B-cell maturation. Differentiation of myeloid cells from patient-derived induced pluripotent stem cells demonstrated increased responsiveness to TLR8. Together, these findings demonstrate that gain-of-function variants in TLR8 lead to a novel childhood-onset IEI with lymphoproliferation, neutropenia, infectious susceptibility, B- and T-cell defects, and in some cases, bone marrow failure. Somatic mosaicism is a prominent molecular mechanism of this new disease.

Interaction Between MDSC and NK Cells in Solid and Hematological Malignancies: Impact on HSCT

Myeloid derived suppressor cells (MDSC) are heterogeneous populations that through the release of soluble factors and/or by cell-to-cell interactions suppress both innate and adaptive immune effector cells. In pathological conditions, characterized by the presence of inflammation, a partial block in the differentiation potential of myeloid precursors causes an accumulation of these immunosuppressive cell subsets both in peripheral blood and in tissues. On the contrary, NK cells represent a major player of innate immunity able to counteract tumor growth. The anti-tumor activity of NK cells is primarily related to their cytolytic potential and to the secretion of soluble factors or cytokines that may act on tumors either directly or indirectly upon the recruitment of other cell types. NK cells have been shown to play a fundamental role in haploidentical hemopoietic stem cell transplantation (HSCT), for the therapy of high-risk leukemias. A deeper analysis of MDSC functional effects demonstrated that these cells are capable, through several mechanisms, to reduce the potent GvL activity exerted by NK cells. It is conceivable that, in this transplantation setting, the MDSC-removal or -inactivation may represent a promising strategy to restore the anti-leukemia effect mediated by NK cells. Thus, a better knowledge of the cellular interactions occurring in the tumor microenvironment could promote the development of novel therapeutic strategies for the treatment of solid and hematological malignances.

Interaction Between MDSC and NK Cells in Solid and Hematological Malignancies: Impact on HSCT

Myeloid derived suppressor cells (MDSC) are heterogeneous populations that through the release of soluble factors and/or by cell-to-cell interactions suppress both innate and adaptive immune effector cells. In pathological conditions, characterized by the presence of inflammation, a partial block in the differentiation potential of myeloid precursors causes an accumulation of these immunosuppressive cell subsets both in peripheral blood and in tissues. On the contrary, NK cells represent a major player of innate immunity able to counteract tumor growth. The anti-tumor activity of NK cells is primarily related to their cytolytic potential and to the secretion of soluble factors or cytokines that may act on tumors either directly or indirectly upon the recruitment of other cell types. NK cells have been shown to play a fundamental role in haploidentical hemopoietic stem cell transplantation (HSCT), for the therapy of high-risk leukemias. A deeper analysis of MDSC functional effects demonstrated that these cells are capable, through several mechanisms, to reduce the potent GvL activity exerted by NK cells. It is conceivable that, in this transplantation setting, the MDSC-removal or -inactivation may represent a promising strategy to restore the anti-leukemia effect mediated by NK cells. Thus, a better knowledge of the cellular interactions occurring in the tumor microenvironment could promote the development of novel therapeutic strategies for the treatment of solid and hematological malignances.

Myeloid-Derived Suppressor Cells in Hematologic Diseases: Promising Biomarkers and Treatment Targets

Myeloid-derived suppressor cells (MDSC) are a heterogeneous group of immature myeloid cells that exist at very low numbers in healthy subjects but can expand significantly in malignant, infectious, and chronic inflammatory diseases. These cells are characterized as early-MDSCs, monocytic-MDSCs, and polymorphonuclear-MDSCs and can be studied on the basis of their immunophenotypic characteristics and their functional properties to suppress T-cell activation and proliferation. MDSCs have emerged as important contributors to tumor expansion and chronic inflammation progression by inducing immunosuppressive mechanisms, angiogenesis and drug resistance. Most experimental and clinical studies concerning MDSCs have been mainly focused on solid tumors. In recent years, however, the implication of MDSCs in the immune dysregulation associated with hematologic malignancies, immune-mediated cytopenias and allogeneic hemopoietic stem cell transplantation has been documented and the potential role of these cells as biomarkers and therapeutic targets has started to attract a particular interest in hematology. The elucidation of the molecular and signaling pathways associated with the generation, expansion and function of MDSCs in malignant and immune-mediated hematologic diseases and the clarification of mechanisms related to the circulation and the crosstalk of MDSCs with malignant cells and other components of the immune system are anticipated to lead to novel therapeutic strategies. This review summarizes all available evidence on the implication of MDSCs in hematologic diseases highlighting the challenges and perspectives arising from this novel field of research.

Autoimmune hemolytic anemia, autoimmune neutropenia and aplastic anemia in the elderly

The physiology of the immune system involves morphologic and functional changes occurring along ageing, with a decrease in immune response and an increase in autoimmune phenomena, even in the absence of overt disese. Autoimmune cytopenias, namely autoimmune hemolytic anemia (AIHA), chronic idiopathic neutropenia (CIN) and aplastic anemia (AA), show different epidemiologic predilection, but are increasingly diagnosed in the elderly, where complications and comorbidities are more frequent. A systematic review of recent literature, shows that comorbidities as well as underlying deficiencies, medications, neoplasms, and, pathophysiologic chronic organ failures, frequently challenge the differential diagnosis in this setting and should always be evaluated and excluded. Complications, particularly infections and thrombosis for AIHA, and bleeding for AA, should be monitored and promptly treated. Treatment choice should be carefully weighed on the individual general condition and comorbidities, granted that intense primary care and support (including evidence-based transfusion policies) are provided. Finally, bone marrow histology is highly advisable in the elderly, both at diagnosis to detect underlying conditions, and along the follow-up to monitor possible bone marrow failure or neoplastic evolution.

Immunoglobulin and B-cell disturbances in patients with chronic idiopathic neutropenia

Chronic idiopathic neutropenia (CIN) is a granulocytic disorder associated with presence of activated, myelosuppressive T-lymphocytes. In the present study we have evaluated constituents of humoral immunity in CIN patients (n=48) compared to healthy controls (n=52). CIN patients displayed lower serum IgG levels due to a reduction in IgG1, IgG3, IgG4 but not IgG2, lower IgA and increased IgM levels compared to controls. The proportion of CD19⁺ cells did not differ between patients and controls; however the proportion of the naïve IgD⁺/CD27^- B-cells was increased and the proportion of class-switched memory IgD^-/CD27⁺ B-cells was decreased in the patients. The percentage of CD40⁺ B-cells did not differ between patients and controls and no aberrations in the CD40-meadiated signal transduction pathway or in CD40-gene polymorphisms were identified. These data provide further evidence that immune disturbances are associated with the pathophysiology of CIN and point out for the first time the implication of the B-cell system.

The relationship between idiopathic cytopenias/dysplasias of uncertain significance (ICUS/IDUS) and autoimmunity

INTRODUCTION

This review examines the several lines of evidence that support the relationship between myelodysplasia and autoimmunity, i.e. their epidemiologic association, the existence of common immune-mediated physiopathologic mechanisms, and the response to similar immunosuppressive therapies. The same relationship is reviewed here considering idiopathic cytopenia of uncertain significance (ICUS) and idiopathic dysplasia of uncertain significance (IDUS), two recently recognized provisional conditions characterized by isolated/unexplained cytopenia and/or dysplasia in <10% bone marrow cells. Areas covered: The review focuses on alterations of cytokine profiles, telomere/telomerase and toll-like receptors, and on increased myelosuppressive mediators and apoptotic markers in both myelodysplasia and autoimmunity. In addition, the presence of an autoimmune reaction directed against marrow precursors is described in refractory/relapsing autoimmune cytopenias (autoimmune hemolytic anemia, immune thrombocytopenia, chronic idiopathic neutropenia), possibly contributing to their evolution to ICUS/IDUS/bone marrow failure syndromes. Expert commentary: The increasing availability of omics methods has fuelled the discussion on the role of somatic mutations in the pathogenesis of IDUS/ICUS, clonal hematopoiesis of indeterminate potential, and clonal cytopenias of undetermined significance, and in their possible evolution. Even more attracting is the involvement of the genetic background/accumulating somatic mutations in cytopenias with autoimmune alterations.

Minor populations of paroxysmal nocturnal hemoglobinuria-type cells in patients with chronic idiopathic neutropenia

Chronic idiopathic neutropenia (CIN) is an acquired disorder of granulopoiesis characterized by increased apoptosis of the bone marrow (BM) granulocytic progenitor cells under the influence of pro-inflammatory mediators and oligoclonal/monoclonal T-lymphocytes. Because patients with immune-mediated BM failure display frequently paroxysmal nocturnal hemoglobinuria (PNH)-type cells in the peripheral blood (PB), we investigated the possible existence of PNH-type cells in 91 patients with CIN using flow cytometry. The patients displayed increased proportions of PNH-type glycophorin A⁺ /CD59^dim and glycophorin A⁺ /CD59^- red blood cells (RBCs), FLAER^- /CD24^- granulocytes, and FLAER^- /CD14^- monocytes, compared to controls (n = 55). A positive correlation was found between the proportions of PNH-type RBCs, granulocytes, and monocytes and an inverse correlation between the number of PB neutrophils and the proportions of PNH-type cell populations. The number of patients, displaying percentages of PNH-type cells above the highest percentage observed in the control group, was significantly increased among patients with skewed compared to those with normal T-cell receptor repertoire suggesting that T-cell-mediated immune processes underlie the emergence of PNH-type cells in CIN. Our findings suggest that patients with CIN display PNH-type cells in the PB at a high frequency corroborating the hypothesis that CIN belongs to the immune-mediated BM failure syndromes.

How we diagnose and treat neutropenia in adults

Neutropenias (NPs), being acute and often transient, or chronic, range from life-threatening conditions with very low absolute neutrophil blood counts (ANC) to disorders characterized by only mild NP and of no obvious significance for health. Many are caused by genetic variations/mutations, e.g. the benign familial NP and the chronic severe NPs (e.g. Kostmann disease). Some of the latter are associated with various bodily malformations. Many of the mild-to-moderate NPs are signs of underlying disorders that need specialized treatments (e.g. HIV, hepatitis, autoimmune disorders, the large granular lymphocyte syndrome). We provide here means for the evaluation of a previously unknown NP, suggest a triage and treatments.

Is chronic neutropenia always a benign disease? Evidences from a 5-year prospective study

AIM

To evaluate infections and oncohematologic evolution in adult patients with chronic idiopathic and autoimmune neutropenia in a prospective study.

PATIENTS AND METHODS

76 consecutive patients were enrolled from September 2008 to April 2012. Complete blood counts and clinical evaluation were performed at enrolment, at month 3, 6, and then every 6 months. Anti-neutrophil antibodies were tested by GIFT method.

RESULTS

Patients (49 chronic idiopathic- and 27 autoimmune neutropenia) were followed for a median of 5 years (range 24-84 months). At enrolment, neutropenia was mild in 44 patients (median neutrophils 1.27×10(3)/μL), moderate in 23 (median 0.8×10(3)/μL), and severe in 9 (median 0.4×10(3)/μL). Neutrophil counts showed a great inter-subject but no intra-subject variability, with lower values in autoimmune neutropenia, in males, and in MGUS cases. Over time, no grade >3 infections occurred; 13/49 chronic idiopathic and 6/27 autoimmune neutropenia patients experienced a grade 2 event, irrespective of mean and nadir neutrophil values. Bone marrow evaluation at enrolment showed reduced cellularity in 23% of cases, and dyserythropoietic features in 55%, with no definite hematologic diagnosis. During the follow-up, 5 cases were diagnosed with NK expansion, 4 with hairy cell leukemia, and 3 with myelodysplasia (1 myelomonocytic leukemia, 1 refractory cytopenia with unilineage dysplasia, and 1 multilineage dysplasia), with a median time to evolution of 30 months.

CONCLUSION

Chronic idiopathic and autoimmune neutropenia, although usually benign, deserve hematological follow-up with a bone marrow evaluation at diagnosis and a re-evaluation in the presence of worsening neutropenia, appearance of additional cytopenias, and lymphocytosis.

CXCR3 axis in patients with primary biliary cirrhosis: a possible novel mechanism of the effect of ursodeoxycholic acid

The CXC chemokines, monokine induced by interferon (IFN)-gamma (MIG) (CXCL9), IFN-gamma-induced protein 10 (IP-10) (CXCL10) and IFN-inducible T cell alpha chemoattractant (I-TAC) (CXCL11), are known to attract CXCR3- (CXCR3A and CXCR3B) T lymphocytes. We investigated MIG, IP-10 and I-TAC mRNAs expression by semi-quantitative multiplex reverse transcription-polymerase chain reaction (RT-PCR) in liver biopsies obtained from patients with a first diagnosis of primary biliary cirrhosis [(PBC) = 20] compared to patients with normal liver biopsy [normal controls (NCs) = 20]. Chemokine production was assessed by enzyme-linked immunosorbent assay (ELISA) in serum. Measurements were repeated 6 months after ursodeoxycholic acid (UDCA) treatment in PBC patients. CXCR3A and CXCR3B mRNAs expression was examined in immunomagnetically sorted CD3(+) peripheral blood lymphocytes (PBL) pre- and post-treatment by RT-PCR. Flow cytometry was used to evaluate the expression of CXCR3(+) PBLs of NCs and PBC patients. A marked mRNA expression of MIG and IP-10 was found in PBC patients. I-TAC mRNA was not detected. In serum of PBC patients there was a significant increase of MIG and IP-10 compared to NCs. Interestingly, there was a significant reduction of these proteins in patients' serum after UDCA treatment. I-TAC was not statistically different between groups. CXCR3A mRNA expression was found in PBLs from PBC patients as well as in NCs. CXCR3B mRNA was expressed in four of 20 (19%) NCs and 20 of 20 PBC patients. Flow cytometry revealed a significantly lower CXCR3 expression in NCs (13·5%) than in PBC (37·2%), which was reduced (28·1%, P < 0·01) after UDCA administration. These data suggest a possible role for CXCR3-binding chemokines and their receptor in the aetiopathogenetic recruitment of lymphocytes in PBC and a new mechanism of action for UDCA.

Genetic associations in acquired immune-mediated bone marrow failure syndromes: insights in aplastic anemia and chronic idiopathic neutropenia

Increasing interest on the field of autoimmune diseases has unveiled a plethora of genetic factors that predispose to these diseases. However, in immune-mediated bone marrow failure syndromes, such as acquired aplastic anemia and chronic idiopathic neutropenia, in which the pathophysiology results from a myelosuppressive bone marrow microenvironment mainly due to the presence of activated T lymphocytes, leading to the accelerated apoptotic death of the hematopoietic stem and progenitor cells, such genetic associations have been very limited. Various alleles and haplotypes of human leucocyte antigen (HLA) molecules have been implicated in the predisposition of developing the above diseases, as well as polymorphisms of inhibitory cytokines such as interferon-γ, tumor necrosis factor-α, and transforming growth factor-β1 along with polymorphisms on molecules of the immune system including the T-bet transcription factor and signal transducers and activators of transcription. In some cases, specific polymorphisms have been implicated in the outcome of treatment on those patients.

Abnormal telomere shortening of peripheral blood mononuclear cells and granulocytes in patients with chronic idiopathic neutropenia

BACKGROUND

Chronic idiopathic neutropenia is characterized by immune-mediated suppression of neutrophil production. Because patients with immune-mediated bone marrow failure syndromes display age-inappropriate telomere shortening in leukocytes, we investigated telomere lengths in peripheral blood mononuclear cells and granulocytes of patients with chronic idiopathic neutropenia.

DESIGN AND METHODS

We studied 37 patients with chronic idiopathic neutropenia and 68 age- and sex-matched healthy controls. Relative telomere length and telomerase reverse transcriptase expression were assessed by a quantitative real time polymerase chain reaction. Telomerase activity was determined by a polymerase chain reaction-based immunoassay.

RESULTS

The mean relative telomere values of peripheral blood mononuclear cells and granulocytes were significantly lower in patients compared to controls, and significantly lower than expected on the basis of the age-adjusted healthy control distribution. The difference in the relative telomere lengths between patients and controls in both peripheral blood mononuclear cells and granulocytes was prominent in those under the age of 50 years. Contrary to the peripheral blood mononuclear cells, in which an inverse correlation was observed between relative telomere values and age, no significant correlation was noted between granulocyte telomere values and patient age. A significant correlation was observed between individual relative telomere values and absolute neutrophil counts. There was no difference in expression of telomerase reverse transcriptase in peripheral blood mononuclear cells between patients and controls but telomerase activity was identified at a significantly higher frequency in controls than in patients. No correlation was found between telomerase activity or telomerase reverse transcriptase expression and relative telomere lengths of peripheral blood mononuclear cells.

CONCLUSIONS

Patients with chronic idiopathic neutropenia display age-inappropriate telomere shortening of peripheral blood cells and low telomerase activity in peripheral blood mononuclear cells. A compensatory increased proliferation of bone marrow hematopoietic progenitor cells in association with lymphocyte replicative exhaustion probably account for these abnormalities.

Increased levels of the high mobility group box 1 protein sustain the inflammatory bone marrow microenvironment in patients with chronic idiopathic neutropenia via activation of toll-like receptor 4

PURPOSE

Chronic idiopathic neutropenia (CIN) is a granulocytic disorder characterized by increased apoptosis of the bone marrow (BM) granulocytic progenitor cells and an inflammatory BM microenvironment. The aim of this study was to investigate the possible involvement of Toll-like receptors (TLRs) in the production of pro-inflammatory mediators in CIN BM.

METHODS

We evaluated the expression of TLRs in patient BM cell subsets and adherent cells of long-term BM cultures (LTBMCs) using flow cytometry. We also examined the activation of TLR-mediated signaling using real-time PCR arrays and explored for potential endogenous TLR-specific ligands in CIN BM.

RESULTS

CIN patients (n = 30) displayed significantly increased expression of surface TLR4 in monocytes of BM and LTBMC adherent cells compared to controls (n = 27). The TLR signaling gene array study in purified BM CD14(+) cells showed that numerous TLR-related genes displayed at least two-fold increase in patients compared to controls. Among the over-expressed genes were genes related to the MyD88-dependent and MyD88-independent pathway suggesting a TLR4-mediated signaling. BM plasma from CIN patients induced the production of pro-inflammatory mediators including interleukin (IL)-6, IL-1β, tumor necrosis factor-α, and IL-8 by autologous BM monocytes, and this effect was abrogated by a specific TLR4 inhibitor. The levels of the high mobility group box 1 protein (HMGB1), representing a TLR4 ligand, were significantly increased in patient LTBMC supernatants compared to controls.

CONCLUSION

These data demonstrate a significant role of BM monocytes in the pathophysiology of CIN through the production of pro-inflammatory cytokines in a TLR4-mediated mechanism under the influence of endogenous ligands such as HMGB1.

Lymphopenia in patients with chronic idiopathic neutropenia is associated with decreased number of T-lymphocytes containing T-cell receptor excision circles

OBJECTIVES

Chronic idiopathic neutropenia (CIN) is a disorder of granulopoiesis characterized by the presence of activated T-lymphocytes that induce/sustain apoptosis of bone marrow (BM) granulocytic progenitors. T-cell lymphopenia is commonly found in CIN. The aim of the study is to probe the mechanisms underlying T-cell lymphopenia in CIN.

METHODS

We investigated parameters of T-cell homeostasis namely the proliferation/apoptotic rate of naïve and memory T cells, the T-cell senescence by telomere measurement, the recent thymic T-cell production through quantification of T-cell receptor rearrangement excision circles (TRECs), and the production of interleukin (IL)-7.

RESULTS

Patients with CIN (n = 44) displayed lower proportion of naïve CD45RA(+) cells within the CD4(+) and CD8(+) cells compared with controls (n = 15). The proportion of apoptotic cells within the CD8(+) fraction was higher in patients compared with controls and was correlated with the percentage of Ki-67(+) cells, indicating an activation-induced accelerated CD8(+) cell death. The TREC content of CD4(+) and CD8(+) cells was lower in patients compared with controls and was correlated with the proportion of CD45RA(+) CD4(+) and CD8(+) cells and with the levels of serum and BM IL-7, which were significantly decreased in the patients. The mean relative telomere length of CD4(+) and CD8(+) cells was significantly lower in patients with CIN compared with age-matched controls.

CONCLUSIONS

The aberrant T-cell expansions associated with the pathogenesis of CIN result in increased proliferation/apoptosis and possibly exhaustion of peripheral blood T cells which, in association with the inadequate compensatory thymic export of new TREC expressing T cells partially because of IL-7 deficiency, may contribute to lymphopenia in CIN.

The role of CD40/CD40 ligand interactions in bone marrow granulopoiesis

The CD40 ligand (CD40L) and CD40 are two molecules belonging to the TNF/TNF receptor superfamily, and their role in adaptive immune system has widely been explored. However, the wide range of expression of these molecules on hematopoietic as well as nonhematopoietic cells has revealed multiple functions of the CD40/CD40L interactions on different cell types and processes such as granulopoiesis. CD40 triggering on stromal cells has been documented to enhance the expression of granulopoiesis growth factors such as granulocyte-colony-stimulating factor (G-CSF) and granulocyte/monocyte-colony-stimulating factor (GM-CSF), and upon disruption of the CD40/CD40L-signaling pathway, as in the case of X-linked hyperimmunoglobulin M (IgM) syndrome (XHIGM), it can lead to neutropenia. In chronic idiopathic neutropenia (CIN) of adults, however, under the influence of an inflammatory microenvironment, CD40L plays a role in granulocytic progenitor cell depletion, providing thus a pathogenetic cause of CIN.

Pathophysiologic mechanisms and management of neutropenia associated with large granular lymphocytic leukemia

Large granular lymphocyte (LGL) syndrome includes a spectrum of clonal T cell and natural killer cell chronic lymphoproliferative disorders. These conditions are thought to arise from chronic antigenic stimulation, while the long-term survival of the abnormal LGLs appears to be sustained by resistance to apoptosis and/or impaired survival signaling. T-cell LGL (T-LGL) leukemia is the most common LGL disorder in the Western world. Despite its indolent course, the disease is often associated with neutropenia, the pathogenesis of which is multifactorial, comprising both humoral and cytotoxic mechanisms. This article addresses the pathogenesis of T-LGL leukemia and natural killer cell chronic lymphoproliferative disorder, as well as that of T-LGL leukemia-associated neutropenia. Furthermore, as symptomatic neutropenia represents an indication for initiating treatment, available therapeutic options are also discussed.

Increased expression of chemokine receptor CCR3 and its ligands in ulcerative colitis: the role of colonic epithelial cells in in vitro studies

Human colonic epithelial cells express T helper type 1 (Th1)-associated chemoattractants, yet little is known about the production of Th2-associated chemoattractants. CCL11/eotaxin-1, CCL24/eotaxin-2 and CCL26/eotaxin-3 are known to attract CCR3-expressing, Th2-polarized lymphocytes. We studied constitutive and inflammation-induced expression and production of CCR3 together with its ligands in the colon and peripheral blood of patients with inflammatory bowel disease (IBD) by flow cytometry, reverse transcription–polymerase chain reaction (RT–PCR) and enzyme-linked immunosorbent assay (ELISA). We further defined the regulated expression of these chemokines by RT–PCR and ELISA using cultured human epithelial cell lines. A higher fraction of peripheral T lymphocytes were found to be positive for CCR3 in patients with ulcerative colitis (UC) compared to Crohn’s disease (CD), while almost no CCR3(+) T cells were found in normal controls (NC). Similarly, higher and more frequent expression of CCR3 was observed in colonic biopsies from patients with UC, regardless of the disease activity, when compared to CD or NCs. Serum CCL11/eotaxin-1 was increased significantly in UC (306 ± 87 pg/ml) and less so in CD (257 ± 43 pg/ml), whereas CCL24/eotaxin-2, and CCL26/eotaxin-3 were increased only in UC. Colonic expression of the three chemokines was minimal in NCs but high in inflammatory bowel diseases (especially UC) and was independent of disease activity. Th2, and to a lesser extent Th1, cytokines were able to induce expression and production of all three eotaxins from colonic epithelial cells in culture. CCR3 and ligands over-expression would appear to be a characteristic of UC. The production of CCR3 ligands by human colonic epithelial cells suggests further that epithelium can play a role in modulating pathological T cell-mediated mucosal inflammation.

Mesenchymal stem cells contribute to the abnormal bone marrow microenvironment in patients with chronic idiopathic neutropenia by overproduction of transforming growth factor-β1

Chronic idiopathic neutropenia (CIN) is a granulopoiesis disorder associated with an inhibitory bone marrow (BM) microenvironment consisting of activated T-lymphocytes and pro-inflammatory mediators. In this study, we investigated the possible involvement of BM mesenchymal stem cells (MSCs) in the pathophysiology of CIN by assessing the frequency and function of BM MSCs in terms of the proliferative/clonogenic characteristics, the differentiation capacity, the potential to produce pro-inflammatory cytokines, and the ability to suppress T-cell proliferation. The frequency, differentiation capacity toward adipocytes, chondrocytes, or osteoblasts, and immunosuppressive potential to inhibit mitogen-induced T-cell proliferation did not differ significantly between patient (n = 14) and normal (n = 21) MSCs. Tumor necrosis factor-α, interleukin-1β, and interleukin-6 levels in MSC supernatants did not differ significantly between patients and controls; however, transforming growth factor (TGF)-β1 levels were significantly elevated in patients, particularly in those displaying the -509C/T TGF-β1 polymorphism. Patient MSCs displayed defective proliferative/clonogenic potential, which could not be attributed to altered cellular survival characteristics or to increased TGF-β1 production as TGF-β1 neutralization did not restore the impaired colony formation by patient MSCs. We conclude that although BM MSCs do not exert a significant role in the immune deregulation associated with CIN, they contribute to the inhibitory microenvironment by overproducing TGF-β1, at least in patients displaying the -509C/T polymorphism.

Effect of lenalidomide therapy on hematopoiesis of patients with myelodysplastic syndrome associated with chromosome 5q deletion

BACKGROUND

Lenalidomide improves erythropoiesis in patients with low/intermediate-1 risk myelodysplastic syndrome and interstitial deletion of the long arm of chromosome 5 [del(5q)]. The aim of this study was to explore the effect of lenalidomide treatment on the reserves and functional characteristics of bone marrow hematopoietic progenitor/precursor cells, bone marrow stromal cells and peripheral blood lymphocytes in patients with low/intermediate-1 risk myelodysplastic syndrome with del(5q).

DESIGN AND METHODS

We evaluated the number and clonogenic potential of bone marrow erythroid/myeloid/megakaryocytic progenitor cells using clonogenic assays, the apoptotic characteristics and adhesion molecule expression of CD34(+) cells by flow cytometry, the hematopoiesis-supporting capacity of bone marrow stromal cells using long-term bone marrow cultures and the number and activation status of peripheral blood lymphocytes in ten patients with low/intermediate-1 risk myelodysplastic syndrome with del(5q) receiving lenalidomide.

RESULTS

Compared to baseline, lenalidomide treatment significantly decreased the proportion of bone marrow CD34+ cells, increased the proportion of CD36(+)/GlycoA(+) and CD36(-)/GlycoA(+) erythroid cells and the percentage of apoptotic cells within these cell compartments. Treatment significantly improved the clonogenic potential of bone marrow erythroid, myeloid, megakaryocytic colony-forming cells and increased the proportion of CD34(+) cells expressing the adhesion molecules CD11a, CD49d, CD54, CXCR4 and the SLAM antigen CD48. The hematopoiesis-supporting capacity of bone marrow stroma improved significantly following treatment, as demonstrated by the number of colony-forming cells and the level of stromal-derived factor-1 alpha and intercellular adhesion molecule-1 in long-term bone marrow culture supernatants. Lenalidomide treatment also increased the proportion of activated peripheral blood T lymphocytes.

CONCLUSIONS

The beneficial effect of lenalidomide in patients with lower risk myelodysplastic syndrome with del(5q) is associated with significant increases in the proportion of bone marrow erythroid precursor cells and in the frequency of clonogenic progenitor cells, a substantial improvement in the hematopoiesis-supporting potential of bone marrow stroma and significant alterations in the adhesion profile of bone marrow CD34(+) cells.

Expression of a splice variant of CXCR3 in Crohn's disease patients; indication for a lymphocyte--epithelial cell interaction

BACKGROUND AND AIM

T-lymphocyte migration is implicated in the pathogenesis of Crohn's disease (CD) and ulcerative colitis (UC). CXC chemokines MIG, IP-10, and I-TAC act by binding to CXCR3 receptor on T-lymphocytes. We investigated the role of these chemokines and their receptor in patients with UC, CD, and normal controls (NC).

METHODS

Chemokine expression and serum levels were examined in colonic biopsies from patients and NC using reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay. HT-29 and Caco2 colonic epithelial cells were studied following in vitro stimulation with proinflammatory (Th1) and Th2-derived cytokines. CXCR3 receptor expression was assessed in CD3+ peripheral blood lymphocytes (PBL) from patients and NC and in stimulated Jurkat leukaemia cells, using RT-PCR and flow cytometry.

RESULTS

Full size CXCR3 mRNA (FS) expression was found in CD3+ PBL from controls and UC, but not from CD patients. In contrast, CD3+ PBL from CD patients showed a marked mRNA expression of the spliced variant CXCR3 (TV). This finding explains the high expression of CXCR3 on CD3+ PBL from CD patients in flow cytometry. Increased chemokine expression and production was found in colonic biopsies and serum from CD compared to UC patients and controls. Stimulation of epithelial cells with proinflammatory cytokines significantly induced chemokine production. The addition of Th2 cytokines had an inhibitory effect. Stimulation of Jurkat cells with cytokines and supernatant conditioned media from epithelial cells induced CXCR3TV expression.

CONCLUSIONS

These data demonstrate that PBL from CD patients express a spliced variant of the CXCR3 receptor and suggest a role for the colonic epithelial cells in T-lymphocyte migration in intestinal inflammation.

Clonal predominance of CD8(+) T cells in patients with unexplained neutropenia

OBJECTIVE

T-cell-mediated autoimmunity may be involved in some cases of idiopathic neutropenia. We hypothesized that a precise T-cell receptor repertoire analysis may uncover cytotoxic T-cell (CTL) expansions that are less pronounced than those seen in T large granular lymphocyte leukemia (T-LGL), but are pathophysiologically analogous and thus can serve as markers of a T-cell-mediated process.

MATERIALS AND METHODS

Using rational algorithms for T-cell receptor analysis and in vivo tracking of CTL responses previously established in our laboratory, we studied patients with unexplained chronic neutropenia (n = 20), T-LGL (n = 15), and healthy controls (n = 12). We further investigated the involvement of soluble inhibitory factors by coculture assays. To determine the level of immune activation, we studied interferon-gamma expression in CD8(+)cells using Taqman polymerase chain reaction.

RESULTS

Fifteen expanded (immunodominant) CTL clones were detected in 12 of 20 patients. In comparison to LGL leukemia, these clones were less immunodominant, but clearly discernible from subclinical lymphoproliferations in controls. As a surrogate of cytotoxic activity, we found markedly increased production of interferon-gamma in most of the neutropenia patients, irrespective of the presence of immunodominant CTL clones.

CONCLUSIONS

These results suggest that, while immunodominant CTL clones are detectable in a proportion of patients only, CTL-mediated pathophysiology may be a general mechanism operating in idiopathic neutropenia. Oligogoclonal CTL expansions in chronic neutropenia may indicate an ongoing autoimmune process, while highly polarized monoclonalities in a subset of neutropenic LGL patients may represent the "extreme" end of the clonal continuum.

Interferon-gamma is increased in patients with primary Sjogren's syndrome and Raynaud's phenomenon

OBJECTIVES

To determine the prevalence of Raynaud's phenomenon (RP) in patients with primary Sjogren's syndrome (pSS) and to identify clinical and immunological characteristics associated with this manifestation. Since increased interferon-gamma (INF-gamma) has been associated with RP, we also compared the INF-gamma production in pSS patients with or without RP.

METHODS

RP was diagnosed if pSS patients presented with characteristic sequence of skin color changes of the digits. In uncertain cases noninvasive vascular tests were performed by ultrasound examination. The secretion of INF-gamma by peripheral blood mononuclear cells was assessed by enzyme-linked immunospot analysis. Further, we examined the expression of different lymphocyte activation markers (CD25, CD45RO, CD69) on CD4+ T-cells by flow cytometric analysis.

RESULTS

Thirty-six of 108 patients with pSS had RP. In these patients we found a significantly increased number of INF-gamma-secreting peripheral blood mononuclear cells compared with patients without RP or to healthy controls. Further, in patients with RP a significantly increased percentage of CD25-positive T-helper cells was detectable. In addition we found an association of leukopenia, thyroiditis, and lower C3 levels with RP in pSS patients.

CONCLUSIONS

These results suggest a pathogenic role of INF-gamma in pSS patients with RP. Whether the RP is immune-mediated or whether INF-gamma directly causes vasospasm still remains to be elucidated.

Normal levels of constitutive and death receptor-mediated apoptosis of peripheral blood neutrophils from patients with chronic idiopathic neutropenia

To investigate the role of neutrophil apoptosis in the pathogenesis of chronic neutropenia, we examined constitutive and death receptor-mediated apoptosis ex vivo of peripheral blood neutrophils obtained from six chronic idiopathic neutropenia (CIN) patients and six healthy adult blood donors. Apoptosis was quantified based on phosphatidylserine externalization and caspase-3 activation in freshly isolated neutrophils or after overnight cultivation of neutrophils in the absence or presence of pro- or anti-apoptotic factors, including the pan-caspase inhibitor, zVAD-fmk. Neutrophils from CIN patients receiving treatment with granulocyte colony-stimulating factor appeared to be more prone to constitutive apoptosis than cells from untreated patients; however, further investigations in larger cohorts of patients are needed to validate these pilot studies. Overall, the level of neutrophil apoptosis was similar in patient and control groups, thus supporting the notion that the underlying defect in these neutropenia patients lies elsewhere, such as in the bone marrow microenvironment.

Evidence for downregulation of erythropoietin receptor in bone marrow erythroid cells of patients with chronic idiopathic neutropenia

OBJECTIVE

The aim of this study is to probe the mechanisms underlying anemia in patients with chronic idiopathic neutropenia (CIN) by evaluating parameters of bone marrow (BM) erythropoiesis.

PATIENTS AND METHODS

Ten CIN patients fulfilling the criteria of anemia of chronic disease, 27 nonanemic CIN patients, and 30 healthy volunteers were enrolled in the study. Reserves and survival characteristics of BM erythroid cells were evaluated using flow cytometry and clonogenic assays. Serum erythropoietin (EPO) was measured with ELISA. Expression of EPO receptors (EPORs) on BM erythroid cells was evaluated by flow cytometry and reverse-transcription polymerase chain reaction.

RESULTS

CIN patients display defective erythropoiesis in addition to previously reported impaired granulopoiesis. Patients have low number of CD34(+)/CD71(+) progenitor and CD36(-)/ Glycophorin A(+) (GlycoA(+)) precursor BM cells, and increased proportion of apoptotic cells within the CD34(+)/CD71(+) and CD36(+)/GlycoA(+) compartments. Burst-forming units erythroid (BFU-Es) in BM mononuclear or purified CD34(+) cells were significantly reduced in the patients. Patient BFU-Es increased significantly following in vitro treatment with tumor necrosis factor-alpha (TNF-alpha) and/or interferon gamma (IFN-gamma)-neutralizing antibodies. Local TNF-alpha and IFN-gamma production was higher in anemic than in nonanemic patients. EPO production was appropriate in the patients, but EPOR expression was significantly reduced in patient GlycoA(+) cells, especially in anemic patients.

CONCLUSION

Impaired BM erythropoiesis in CIN patients is probably the result of increased local production of TNF-alpha and IFN-gamma that induce apoptosis, cell growth inhibition, and downregulation of EPOR expression on erythroid cells. We suggest that anemia in CIN patients displays overlapping pathophysiologic features with anemia of chronic disease.

Impaired megakaryopoiesis in patients with chronic idiopathic neutropenia is associated with increased transforming growth factor β1 production in the bone marrow

Patients with chronic idiopathic neutropenia (CIN) display relatively low peripheral blood platelet counts and hypo-lobulated megakaryocytes in the bone marrow (BM). The underlying pathogenetic mechanismswere probed by studying the reserves and clonogenic potential of BM megakaryocytic progenitor cells using flow-cytometry and a collagen-based clonogenic assay for the identification of megakaryocyte colony-forming units (CFU-Meg). Thrombopoietin (TPO) and transforming growth factor-beta1 (TGFbeta1) levels were also evaluated in long-term BM culture supernatants using an enzyme-linked immunosorbent assay. CIN patients (n = 39) showed a low proportion of BM CD34(+)/CD61(+) megakaryocytic progenitor cells and low frequency of early and mixed CFU-Meg in the BM mononuclear, but not CD34(+), cell fraction, compared with healthy controls (n = 20). TPO and TGFbeta1 levels were significantly higher in patients compared with controls. TPO levels inversely correlated with platelet counts whereas TGFbeta1 values correlated inversely with CD34(+)/CD61(+) and CFU-Meg megakaryocytic progenitor cell numbers and positively with TPO levels. The addition of an anti-TGFbeta1 neutralising antibody significantly increased the numbers of CFU-Meg in CIN patients but not in controls, compared with baseline. These data suggest that increased local production of TGFbeta1 probably affects the BM megakaryocytic progenitor cell growth in CIN whereas the compensatory production of TPO finally balances the TGFbeta1-induced inhibitory effect.

Effect of cA2 Anti–Tumor Necrosis Factor-α Antibody Therapy on Hematopoiesis of Patients with Myelodysplastic Syndromes

PURPOSE

Tumor necrosis factor alpha (TNF-alpha) plays a prominent role in the pathophysiology of myelodysplastic syndromes (MDS). The aim of this study was to explore the biological and immunoregulatory effect of the treatment with the anti-tumor necrosis factor-alpha monoclonal antibody cA2 on bone marrow (BM) progenitor/precursor and stromal cells and lymphocyte subsets, as well as the clinical response in MDS patients.

EXPERIMENTAL DESIGN

Ten low-intermediate risk MDS patients received i.v. cA2 (3 mg/kg) at weeks 0, 2, 6, and 12. The number, survival, and clonogenic potential of BM progenitor/precursor cells, the hematopoiesis-supporting capacity of BM stromal cells, and the lymphocyte activation status were investigated in the patients at baseline and following treatment using flow cytometry, clonogenic assays, and long-term BM cultures (LTBMC). Clinical response was evaluated according to standardized criteria.

RESULTS

cA2 administration reduced the proportion of apoptotic and Fas+ cells in the CD34+ cell compartment (P = 0.0215 and P = 0.0344, respectively) and increased the clonogenic potential of BM mononuclear and CD34+ cells (P = 0.0399 and P = 0.0304, respectively) compared with baseline. The antibody reduced tumor necrosis factor-alpha levels in LTBMC supernatants (P = 0.0043) and significantly improved the hematopoiesis-supporting capacity of LTBMC adherent cells. The proportion of activated peripheral blood and BM T-lymphocytes decreased significantly after treatment, suggesting an immunomodulatory effect of cA2. Two patients displayed minor hematologic responses whereas the remaining patients displayed stable disease with no disease progression.

CONCLUSIONS

The encouraging biological insights from cA2 administration may be useful in conducting further clinical trials using cA2 for selected MDS patients, particularly those with evidence of immune-mediated inhibition of hematopoiesis.

Increased levels of soluble flt-3 ligand in serum and long-term bone marrow culture supernatants in patients with chronic idiopathic neutropenia

The levels of serum and long-term bone marrow culture supernatant soluble flt-3 ligand (sFL) were determined in 54 patients with chronic idiopathic neutropenia (CIN) and 16 normal controls. Both serum and supernatant sFL levels were significantly increased in the patients compared with controls. Individual sFL values inversely correlated with the number of circulating neutrophils and the proportion of bone marrow CD34+ cells. Supernatant sFL values positively correlated with the levels of supernatant G-CSF. These findings suggest that the impaired myelopoiesis in CIN patients is accompanied by a compensatory mechanism attempting to increase the neutrophil production at the myeloid progenitor cell level.

Soluble c-kit ligand production by bone marrow stromal cells is independent of the degree of neutropenia in patients with chronic idiopathic neutropenia

The levels of soluble c-kit ligand (sKL), also known as Steel factor or stem cell factor, were measured in blood serum and long-term bone marrow culture supernatants of 81 patients with chronic idiopathic neutropenia (CIN) and 22 normal controls using a commercially available enzyme-linked immunosorbent assay (ELISA). We found that the levels of serum and culture supernatant sKL did not differ significantly between patients and control subjects and that both serum and supernatant values of the cytokine did not correlate with the number of circulating neutrophils. Furthermore, we found that the levels of the culture supernatant granulocyte colony-stimulating factor (G-CSF), also measured by ELISA, were significantly increased in the patients compared to controls but individual G-CSF values did not correlate with the values of supernatant sKL. These findings suggest that sKL-producing cells continuously secrete sKL and that cytokine secretion is independent of the degree of neutropenia or the levels of supernatant G-CSF in patients with CIN.

Normal bone marrow hematopoietic stem cell reserves and normal stromal cell function support the use of autologous stem cell transplantation in patients with multiple sclerosis

Bone marrow (BM) stem cell reserves and function and stromal cell hematopoiesis supporting capacity were evaluated in 15 patients with multiple sclerosis (MS) and 61 normal controls using flow cytometry, clonogenic assays, long-term BM cultures (LTBMCs) and enzyme-linked immunosorbent assays. MS patients displayed normal CD34+ cell numbers but a low frequency of colony-forming cells (CFCs) in both BM mononuclear and purified CD34+ cell fractions, compared to controls. Patients had increased proportions of activated BM CD3+/HLA-DR+ and CD3+/CD38+ T cells that correlated inversely with CFC numbers. Patient BM CD3+ T cells inhibited colony formation by normal CD34+ cells and patient CFC numbers increased significantly following immunomagnetic removal of T cells from BMMCs, suggesting that activated T cells may be involved in the defective clonogenic potential of hematopoietic progenitors. Patient BM stromal cells displayed normal hematopoiesis supporting capacity indicated by the CFC number in the nonadherent cell fraction of LTBMCs recharged with normal CD34+ cells. Culture supernatants displayed normal stromal derived factor-1 and stem cell factor/kit ligand but increased flt-3 ligand levels. These findings provide support for the use of autologous stem cell transplantation in MS patients. The low clonogenic potential of BM hematopoietic progenitors probably reflects the presence of activated T cells rather than an intrinsic defect.