Chronic idiopathic neutropenia: granulopoietic assessment by both marrow culture and granulocyte kinetics

Non-immune chronic idiopathic neutropenia of adult: an overview

There is strong evidence that non-immune chronic idiopathic neutropenia of adult is a cytokine-mediated syndrome characterized by (a) neutropenia of varying degree associated with a low number of lineage-specific CD34+ cells and increased production of inhibitors of hematopoiesis, including transforming growth factor-beta1 and tumor necrosis factor-alpha; (b) lymphopenia due to selective loss of primed/memory T-cells and NK cells; (c) increased splenic volume on ultrasonography in 48.1% of patients; (d) osteopenia and/or osteoporosis in 60.0% of patients; (e) anemia, mostly of the type of anemia of chronic disease, in 15.6% of patients; (f) features of chronic antigenic stimulation, including increased proportion of bone marrow plasma cells, increased serum levels of IgG1 and/or IgA, increased frequency of monoclonal gammopathy of undetermined significance, increased frequency of antinuclear antibodies with specific reactivity, and increased serum levels of circulating immune complexes; and (g) increased concentrations of a variety of macrophage-derived pro-inflammatory cytokines and chemokines capable of affecting bone metabolism, bone marrow function, and leukocyte trafficking. All these findings are suggestive of the existence of an unrecognized low-grade chronic inflammatory process which may be involved in the pathogenesis of the disorder. Neutropenia in these patients is probably the result of a combination of at least three factors, reduced neutrophil production in bone marrow, enhanced neutrophil extravasation, and increased sequestration and/or extravasation of neutrophils into the spleen.

Patients with non-immune chronic idiopathic neutropenia syndrome have increased splenic volume on ultrasonography

Clinically detectable splenomegaly is rarely seen in patients with non-immune chronic idiopathic neutropenia syndrome (NI-CINS). Using ultrasound, we estimated splenic volume in 52 NI-CINS patients and 14 age- and sex-matched normal controls by determining the "corrected splenic index" (CSI) from the product of length, width and thickness of the organ expressed in cm3/m2 body surface area. We found that CSI was significantly higher in the group of patients compared to controls (202.8 +/- 82.0 vs. 133.8 +/- 28.1 cm3/m2, P=0.003), and that individual CSI values was inversely correlated with the number of circulating neutrophils (r=-0.5097, P < 0.0001). About 48.1% of the patients had CSI above 190 cm3/m2 body surface, representing the upper 95% confidence limit of values found in the controls. Patients also had increased serum concentrations of pro-inflammatory cytokines and chemokines mainly produced by activated macrophages (IL-1beta, TNF-alpha, RANTES and IL-8), as well as increased serum levels of soluble cell adhesion molecules derived from activated endothelium (sE-Selectin, sICAM and sVCAM). We hypothesize that the increased splenic volume in NI-CINS patients may be due to the accumulation of activated macrophages inside the spleen, possibly as the result of an unrecognized low-grade chronic inflammatory process. The nature of such an inflammation is unknown. A study was designed to search for viral or bacterial genomic material in patients' bone marrow stromal macrophages in which the unknown causal agent might be located.

Patients with chronic idiopathic neutropenia of adults have increased serum concentrations of inflammatory cytokines and chemokines

Serum levels of inflammatory cytokines and chemokines were measured in 132 patients with chronic idiopathic neutropenia of adults (CINA) and 34 healthy volunteers (controls) using commercially available micro-ELISA determination kits. We found that serum interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), transforming growth factor-beta(1) (TGF-beta(1)), and soluble tumor necrosis factor receptor p55 (sTNF-RI) were all significantly increased in CINA patients compared to controls. Individual cytokine values inversely correlated with the number of circulating neutrophils. Serum levels of interleukin-8 (IL-8) and RANTES, two potent chemokines for neutrophils and lymphocytes, respectively, were also significantly increased in the group of patients and they inversely correlated with the number of circulating neutrophils. Contrarily, serum levels of interleukin-4 (IL-4), interferon-gamma (IFN-gamma), soluble CD23 (sCD23), and soluble interleukin-2 receptor (sIL-2R) did not show any significant change in the patients studied. We assume that CINA patients have increased serum concentrations of inflammatory cytokines and chemokines mainly produced by activated macrophages, while they disclose normal levels of inflammatory molecules mainly released from activated lymphocytes. These findings provide further evidence for an underlying low-grade chronic inflammatory process in CINA patients, as we previously have suggested. If this chronic inflammation is really the cause of the disorder or it simply represents the result of neutropenia remains to be elucidated.

Low frequency of myeloid progenitor cells in chronic idiopathic neutropenia of adults may be related to increased production of TGF-beta1 by bone marrow stromal cells

Previous studies in our laboratory have shown that patients with chronic idiopathic neutropenia of adults (CINA) have increased serum levels of inflammatory cytokines including IL-1beta. Since IL-1beta may affect bone marrow stromal cell function, a study was designed to investigate the capacity of patients' stromal cells to produce adequate amounts of haemopoietic growth factors or excessive amounts of inhibitors of myelopoiesis in long-term bone marrow cultures (LTBMCs). The study was carried out on 52 CINA patients and 19 normal controls. We found that CINA patients had significantly low numbers of marrow lineage-specific CD34+ cells, including CFU-GM and CD34+/CD33+ cells. Stromal cells from patients' LTBMCs failed to stimulate CFU-GM colony formation by normal marrow cells in a manner comparable to that of stromal cells of controls. Patients' LTBMC supernatants had normal or increased amounts of G-CSF. Detectable amounts of supernatant GM-CSF were found in 35% of patients and 19% of controls. IL-3 and MIP-1alpha were not detected in any supernatant fluid. Moreover, supernatants from patients' LTBMCs had increased concentrations of IL-6 and TGF-beta1, which strongly correlated with serum IL-1beta. About 82% of our patients had TGF-beta1 values higher than the upper limit of values found in the controls. Individual TGF-beta1 values inversely correlated with the number of circulating neutrophils and the frequency of marrow CD34+/CD33+ cells. We suggest that increased levels of serum IL-1beta, resulting from an underlying low-grade chronic inflammatory process, may stimulate marrow stromal cells to produce both haemopoietic growth factors and inhibitors of myelopoiesis. Since steady-state myelopoiesis results from a balance between negative- and positive-acting cytokines, it seems very probable that the increased production of TGF-beta1 by bone marrow microenvironment in CINA patients may suppress myelopoiesis and contribute, to some extent, to the pathogenesis of neutropenia in affected subjects.

Granulopoietic precursors in chronic neutropenia

11 patients with chronic neutropenia were evaluated. In 6 patients low numbers of CFU-DG were observed. Only 3 of these patients also had low CFU-C numbers, suggesting that these two precursors are not identical. Bone marrow samples from 2 patients were restudied a year later. The number of CFU-DG remained low while CFU-C numbers increased to control range in 1 patient. Studies for serum inhibitors were negative. No cytogenetic abnormalities were observed. This study suggests that abnormalities at different levels in the haemopoietic precursor cell hierarchy can be detected either simultaneously or independently in patients with chronic neutropenia.

In vitro clonogenic assays in selective neutropenia

Granulocyte-monocyte colony forming cell (GM-CFC) concentration and the proportion of GM-CFC in DNA synthesis (S) were determined in 43 patients with varying degrees of selective neutropenia, including 5 patients who were normal extremes (2.0-2.5 x 10(9) neutrophils/1), to study the diagnostic and prognostic significance of clonogenic assays and to determine the response of the committed myeloid stem cell to neutropenia. The proportion of GM-CFC in S proved to be a more useful parameter than the GM-CFC concentration. 75% of the patients with greater than 60% GM-CFC in S returned to normal within 1 month. Patients with less than 20% GM-CFC in S had at least a 10 times greater incidence of developing a malignant or autoimmune disease than the other 28 patients. The 11 patients with 41-51% in GM-CFC in S had greater than 1 x 10(9) neutrophils/1 and no significant clinical problems but all have remained mildly neutropenic for a long period. An indirect relationship existed between the degree of neutropenia and the proportion of GM-CFC in S (r = -0.70).