Impaired hematopoiesis in paroxysmal nocturnal hemoglobinuria/aplastic anemia is not associated with a selective proliferative defect in the glycosylphosphatidylinositol-anchored protein-deficient clone

Paroxysmal nocturnal hemoglobinuria (PNH) results from somatic mutations in the PIG-A gene, leading to poor presentation of glycosylphosphatidylinositol (GPI)-anchored surface proteins. PNH frequently occurs in association with suppressed hematopoiesis, including frank aplastic anemia (AA). The relationship between GPI-anchored protein expression and bone marrow (BM) failure is unknown. To assess the hematopoietic defect in PNH, the numbers of CD34+ cells, committed progenitors (primary colony-forming cells [CFCs]), and long-term culture-initiating cells (LTC-ICs; a stem cell surrogate) were measured in BM and peripheral blood (PB) of patients with PNH/AA syndrome or patients with predominantly hemolytic PNH. LTC-IC numbers were extrapolated from secondary CFC numbers after 5 weeks of culture, and clonogenicity of LTC-ICs was determined by limiting dilution assays. When compared with normal volunteers (n = 13), PNH patients (n = 14) showed a 4.7-fold decrease in CD34+ cells and an 8.2-fold decrease in CFCs. LTC-ICs in BM and in PB were decreased 7.3-fold and 50-fold, respectively. Purified CD34+ cells from PNH patients had markedly lower clonogenicity in both primary colony cultures and in the LTC-IC assays. As expected, GPI-anchored proteins were decreased on PB cells of PNH patients. On average, 23% of monocytes were deficient in CD14, and 47% of granulocytes and 58% of platelets lacked CD16 and CD55, respectively. In PNH BM, 27% of CD34+ cells showed abnormal GPI-anchored protein expression when assessed by CD59 expression. To directly measure the colony-forming ability of GPI-anchored protein-deficient CD34+ cells, we separated CD34+ cells from PNH patients for the GPI+ and GPI-phenotype; CD59 expression was chosen as a marker of the PNH phenotype based on high and homogeneous expression on fluorescent staining. CD34+ CD59+ and CD34+ CD59-cells from PNH/AA patients showed similarly impaired primary and secondary clonogeneic efficiency. The progeny derived from CD34+ CD59- cells were both CD59- and CD55-. A very small population of CD34+ CD59- cells was also detected in some normal volunteers; after sorting, these CD34+ CD59- cells formed normal numbers of colonies, but their progeny showed lower CD59 levels. Our results are consistent with the existence of PIG-A-deficient clones in some normal individuals. In PNH/AA, progenitor and stem cells are decreased in number and function, but the proliferation in vitro is affected similarly in GPI-protein-deficient clones and in phenotypically normal cells. As measured in the in vitro assays, expansion of PIG-A- clones appears not be caused by an intrinsic growth advantage of cells with the PNH phenotype.

Aplastic anemia in eosinophilic fasciitis: responses to immunosuppression and marrow transplantation

Eosinophilic fasciitis (EF) is a rare connective tissue disorder which is frequently associated with hematologic disorders, especially aplastic anemia (AA) and variants (amegakaryocytic thrombocytopenia). The prognosis for AA with EF has generally been poor, but a few reports suggest a role for immunosuppressive therapy. We have seen four cases of AA complicating EF. All received corticosteroids and anti-thymocyte globulin without any benefit. One patient died of bleeding and infection. A second achieved unmaintained partial remission after two courses of cyclosporine A, although he had difficulty with side effects. Two patients received bone marrow transplants and both initially engrafted well. One had received marrow from a phenotypically HLA-matched parent and died of late graft failure. The second transplanted patient appears to be the only reported case of long term cure of both the AA and EF. Our four patients constitute the largest reported series of AA with EF and shed light on clinical aspects of the disease, and on the pathogenesis, particularly on responsiveness to different therapies; furthermore, there are implications to the treatment of AA in general.

A new syndrome of familial aplastic anemia and chronic liver disease

This report describes a new familial syndrome characterized by a combination of bone marrow failure and chronic liver disease. This disorder appears to be genetic in origin with an autosomal dominant inheritance and was characterized by hyperactivity of the immune system with increased activated cytotoxic T lymphocytes in peripheral blood and bone marrow and the presence of gamma-interferon messenger RNA in bone marrow of several cases.

Flt3 ligand level reflects hematopoietic progenitor cell function in aplastic anemia and chemotherapy-induced bone marrow aplasia

Flt3 ligand (flt3L) is a member of a small family of cytokines acting as tyrosine kinase receptor ligands that stimulate the proliferation of primitive hematopoietic progenitors in vitro. To gain insight into the physiological role of flt3L in early hematopoiesis, levels of flt3L were determined in serum of patients with multilineage bone marrow failure and related to the severity of stem cell depletion. In patients with aplastic anemia (AA) and in cancer patients with chemotherapy-induced transient suppression of hematopoiesis, flt3L fluctuated in an inverse relationship to the degree of bone marrow failure. In severe AA at diagnosis, levels of circulating soluble flt3L were highly elevated (2,653 +/- 353 pg/mL) as compared with normal blood serum values of 14 +/- 39 pg/mL. Flt3L returned to near normal levels within the first 3 months following successful bone marrow transplantation and in autologous remission induced by immunosuppressive therapy with antilymphocyte globulin (ALG; 100 +/- 31 and 183 +/- 14 pg/mL, respectively). In contrast, rejection of the graft or relapse of the disease after ALG was accompanied by an increase to high pretreatment concentrations of the circulating cytokine (3,770 +/- 2,485 and 1,788 +/- 233 pg/mL, respectively). Flt3L in serum inversely correlated with the colony-forming ability of AA bone marrow precursors in vitro (R = -.86), indicating that the concentration of the ligand reflects hematopoiesis at the progenitor cell level. Flt3L increased to 2,500 pg/mL in the serum of leukemia patients during chemoradiotherapy-induced bone marrow suppression and returned to normal values along with hematopoietic recovery. Expression of the membrane-bound form of flt3L was significantly elevated in mononuclear bone marrow and peripheral blood cells from patients with severe pancytopenia, suggesting de novo synthesis of the factor in response to bone marrow failure. The data provide a strong argument for the involvement of flt3L in the regulation of early hematopoiesis in vivo.

Human thrombopoietin levels are high when thrombocytopenia is due to megakaryocyte deficiency and low when due to increased platelet destruction

Thrombopoietin (TPO), the ligand for c-mpl, stimulates proliferation of committed megakaryocytic progenitors and induces maturation of megakaryocytes. To better understand factors regulating TPO levels, we measured blood levels of TPO in patients with impaired platelet production due to aplastic anemia (AA) and with platelet destructive disorders, including idiopathic thrombocytopenic purpura (ITP), posttransfusion purpura (PTP), drug purpura (DP), and X-linked thrombocytopenia (XLTP). The TPO receptor capture enzyme immunoassay (EIA) used had a detection limit of integral of approximately-150 to 200 pg/mL. TPO was undetectable in 88 of 89 normal individuals. Eighteen of 19 patients with AA and a mean platelet count (MPC) of 18,000/microliters (2,000 to 61,000/microliters) had markedly elevated TPO levels (mean, 1,467 pg/mL; range, 597 to 3,834 pg/mL). Eight AA patients who responded to immunosuppressive therapy with their MPC increasing to 140,000/microliters (92,000 to 175,000/microliters) had substantial decreases in TPO (mean, 440 pg/mL; range, 193 to 771 pg/mL). Initial TPO levels did not differ significantly between responders and nonresponders. In contrast, all 21 patients with ITP and an MPC of 16,000/microliters (1,000 to 51,000 /microliters) had undetectable TPO levels, as did 6 patients with acute PTP or DP and 2 patients with XLTP. Megakaryocyte mass, reflected in the rate of platelet production, appears to be the major determinant of TPO levels in thrombocytopenic patients rather than circulating platelet levels per se. Measurement of serum TPO may be useful in differentiating thrombocytopenias due to peripheral destruction from those due to thrombopoietic failure.

Interferon-gamma constitutively expressed in the stromal microenvironment of human marrow cultures mediates potent hematopoietic inhibition

Clinical and laboratory studies have suggested involvement of interferon-gamma (IFN-gamma) in the pathophysiology of aplastic anemia. T cells from aplastic anemia (AA) patients secrete IFN-gamma in vitro, activated cytotoxic lymphocytes infiltrate aplastic bone marrow (BM), and IFN-gamma mRNA, not detected in normal BM, is present in BM from most AA patients. Many patients respond to immunosuppressive therapy with antithymocyte globulin and cyclosporine. Using long-term BM cultures (LTBMC) as a tissue culture model of hematopoiesis, we show that IFN-gamma is a potent inhibitor in the long-term culture-initiating cell (LTC-IC) assay, the best in vitro surrogate test for human hematopoietic stem cells, as well as of the output of committed progenitor cells (colony-forming unit-granulocyte-macrophage [CFU-GM] and burst-forming unit-erythroid [BFU-E]). In LTBMC, continuous addition of relatively high IFN-gamma concentrations (1,000 U/mL weekly or 200 U/mL every 2 days) was required for inhibition of secondary colony formation, a measure of LTC-IC number and clonogenicity. To mimick local production of IFN-gamma, human stromal cells were engineered by retroviral-mediated gene transfer to express a transduced IFN-gamma gene. IFN-gamma secreted by stromal cells was far more potent than exogenous IFN-gamma in its effects in the LTC-IC assay. For purified CD34+ cells culture in the presence of IFN-gamma stroma dramatically reduced secondary colony numbers as well as production of CFU-GM and BFU-E. Supernatants from these cultures contained only about 20 U/mL of IFN-gamma; this quantity of cytokine, when added to LTBMC, had little effect on hematopoiesis. The mechanism of hematopoietic suppression was related to the inhibition of cell cycle progression and induction of apoptosis of CD34+ cells. There was no apparent effect of local low-level IFN-gamma production on stromal cell function, as reflected in cell morphology, cell surface phenotype, or expression of hematopoietic growth factor genes. LTBMC with genetically altered stromal cells offers an in vitro model of immune suppression of hematopoiesis in AA and may be helpful in testing certain therapeutic modalities. We infer from our data that local production of low levels of inhibitory cytokine is sufficient to markedly inhibit hematopoiesis and to destroy stem cells and more mature progenitor cells.

Ocular chloramphenicol and aplastic anaemia. Is there a link?

The question of a link between the use of topical ocular chloramphenicol and the incidence of aplastic anaemia continues to be a controversial issue in ophthalmological spheres. At present topical ocular chloramphenicol is widely used in the UK for the treatment of conjunctivitis, whereas it is very rarely prescribed for this indication in the U.S. Individual policies vary around the rest of the world. The evidence for and against any association between topical and ocular chloramphenicol and an increased risk of aplastic anaemia is reviewed, and the reasons behind the current prescribing policies are clarified. The discussion generated in the literature over the past 2 years over this issue is considered, along with the published debate from the past 3 decades. The debate is not conclusive, but by presenting or referencing the specific case reports and the published opinions of various experts, we hope to enable the reader to make his or her own informed decision as to whether use of the topical preparation of chloramphenicol should be considered by the ophthalmological community.

Uncontrolled triggering of programmed cell death (apoptosis) in haematopoietic stem cells: a new hypothesis for the pathogenesis of aplastic anaemia

The cause of bone marrow failure in aplastic anaemia (AA) is still unknown; however, it is clear that acquired AA is a heterogeneous disease including basically different pathophysiological conditions. Causative agents, clinically associated with AA, possibly exert their action through restricted pathways. Some theoretical and experimental data show that programmed cell death (PCD) or apoptosis is physiologically important in normal haematopoiesis and could be involved in the pathophysiological events responsible for the development of AA. Therefore, it is intriguing to hypothesize that the pathogenetic mechanism underlying most cases of acquired AA could be represented by an excessive and/or uncontrolled triggering of PCD in haematopoietic stem cells. Investigations to test this hypothesis are proposed.

Bone marrow failure in children

Bone marrow failure in the pediatric patient places the hematologist at the junction of clinical medicine, cellular biology, and molecular genetics. The pathophysiology of these disorders is rapidly being elucidated in many laboratories. Treatments such as bone marrow transplantation and the nascent modality of gene therapy are firmly grounded in these modern sciences. This year's progress in the understanding, diagnosis, and treatment of a wide variety of predominantly pediatric bone marrow failure states is a direct result of the union between the "laboratory bench and the patient bedside."

Hematopoietic tissue repair under chronic low daily dose irradiation

The capacity of the hematopoietic system to repair constantly accruing cellular damage under chronic, low daily dose gamma irradiation is essential for the maintenance of a functional hematopoietic system, and, in turn, long term survival. In certain individuals, however, such continuous cycles of damage and repair provide an essential inductive environment for selected types of hematopathologies, e.g., myeloid leukemia (ML). In our laboratory we have been studying temporal and causal relationships between hematopoietic capacity, associated repair functions, and propensities for hematologic disease in canines under variable levels of chronic radiation stress (0.3-26.3 cGy d-1). Results indicate that the maximum exposure rate tolerated by the hematopoietic system is highly individual-specific (three major responding subgroups identified) and is based largely on the degree to which repair capacity, and, in turn, hematopoietic restoration, is augmented under chronic exposure. In low-tolerance individuals (prone to aplastic anemia, subgroup 1), the failure to augment basic repair functions seemingly results in a progressive accumulation of genetic and cellular damage within vital progenitorial marrow compartments (particularly marked within erythroid compartments) that results in loss of reproductive capacity and ultimately in collapse of the hematopoietic system. The high-tolerance individuals (radioaccomodated and either prone- or not prone to ML, subgroup 2 & 3) appear to minimize the accumulating damage effect of daily exposures by extending repair functions, which preserves reproductive integrity and fosters regenerative hematopoietic responses. As the strength of the regenerative response manifests the extent of repair augmentation, the relatively strong response of high- tolerance individuals progressing to patent ML suggests an insufficiency of repair quality rather than repair quantity. The kinetics of these repair-mediated, regenerative hematopoietic responses within the major subgroups are under study and should provide useful insights into the nature of hematopoietic accommodation (or its failure) under greatly extended periods of chronic, low-daily-dose ionizing radiation exposure.

Immunosuppressive therapy in bone marrow aplasia: the stroma functions normally to support hematopoiesis

In aplastic anemia (AA) patients responsive to antilymphocyte globulin (ALG) therapy, abnormalities in both stroma and progenitor cell (PC) pool have been described. The relevance of each pathophysiologic defect was characterized in 16 individuals, and data were compared to results from seven normal volunteers. Bone marrow mononuclear cells were split into two fractions. Stromal layers (SL) were prepared from the first, and a CD34+ enriched population was obtained by immunomagnetic selection from the second. In cross-culture experiments, 1 x 10(4) of the latter from patients or controls were seeded on preformed SL, and adhesive PC were scored for the formation of blast colonies (CFU-Bl) on day 5 of culture. Nonadherent progenitors were recovered and quantitated in a standard clonogenic assay (CFU-GM). There were significantly fewer CD34+ cells in the AA group (median 0.65%, SD 0.39%, vs. 1.62%, SD 1.4%; p = 0.002). No morphological or cytologic differences between normal and aplastic SL were detected. Both equally supported the growth of CFU-Bl from normal progenitors (mean 117, SD 20.4, and 103.1, SD 30.4), while this value was reduced for the aplastic PC (mean 41.06, SD 42.9; p = 0.0002, exact two-tailed test). Similarly, the AA nonadherent PC had a decreased CFU-GM growth (mean 142.6, SD 104.8, vs. mean 361.7; SD 91.3), with a lower total clonogenic output (p = 0.0009). We conclude that aplastic stroma appropriately supports the growth of normal progenitors, whereas the depressed clonogenicity of the corresponsing population derived from AA is unrelated to their attachment to SL but intrinsic to the CD34+ cells, whether adherent or not.

Treatment of aplastic anemia in children with high dose methyl prednisolone

Severe aplastic anemia (SAA) in children has been previously treated with high dose methyl prednisolone (HDMP) with favorable results. We reviewed our experience with intravenous HDMP. Seven children with a diagnosis of SAA confirmed on bone marrow biopsy were treated with 300 mg/kg total dose of intravenous HDMP over a 4 week period. Patients were closely monitored for response and side effects. HDMP was well tolerated except for hyperglycemia in one case. Six of the seven patients showed no response to HDMP. This observation is in stark contrast with previous trials on use of HDMP in SAA. It is concluded that HDMP should be reserved only for patients with milder bone marrow hypoplasia.

Persistent growth impairment of bone marrow stroma after antilymphocyte globulin treatment for severe aplastic anaemia and its association with relapse

Bone marrow from 65 patients with aplastic anaemia (AA) was tested for stroma growth in short term cultures (2 weeks) and for colony formation by haemopoietic precursor cells during the course of their disease. In 18 untreated patients, mean stroma growth was 30% of normal and colony formation was virtually absent. After treatment with immunosuppression (IS), as estimated from 90 examinations in 54 patients, stroma growth was approximately 50% and colony growth approximately 10% of normal. Growth impairment of stroma and haemopoietic precursors persisted for 10 and more years after IS. Results of 2-week stroma cultures were compared with results of long term bone marrow cultures in 10 AA patients and 4 controls. At 2 weeks, growth of aplastic marrow was delayed compared to normal, but this difference became less evident with prolonged incubation time. In vitro growth abnormalities were compared with the clinical evolution after IS. The development of late haematological complications (paroxysmal nocturnal haemoglobinuria (PNH)) and myelodysplastic syndrome (MDS), did not correlate with the degree of stroma growth impairment. However, relapse of aplasia was associated with poor stroma growth: 8/29 patients with stroma confluence of < or = 30% during haematological remission versus 1/25 with stroma confluence of > 30% relapsed. We conclude that (i) the haematopoietic microenvironment is frequently coinvolved in the disease process of AA, (ii) a defect is detected in short term rather than in long term stroma cultures and, (iii) relapse is more frequent in patients with poor stroma growth.

Effect of haemoglobin and endogenous erythropoietin on hypothalamic-pituitary thyroidal and gonadal secretion: an analysis of anaemic (high EPO) and polycythaemic (low EPO) patients

OBJECTIVE

Correction of anaemia with recombinant human erythropoietin (rHu-EPO) improves the responsiveness of thyroidal and gonadal axes to exogenous TRH and GnRH in chronic haemodialysis patients, but the mechanisms remain to be fully elucidated. In order to assess the influences of endogenous erythropoietin on the hypothalamo-hypophyseal thyroidal and gonadal axes, we studied the response of polycythaemic and anaemic patients, in comparison to normal controls, after the administration of exogenous TRH and GnRH.

DESIGN

Exogenous hypothalamic factors, 500 micrograms TRH and 100 micrograms GnRH, were administered as a bolus and blood samples were obtained over a 3-hour period at 30, 60, 90, 120 and 180 minutes.

PATIENTS

Five male polycythaemic patients (low EPO), three male anaemic patients (high EPO) and six normal age and sex matched controls were studied.

MEASUREMENTS

Blood samples were centrifuged immediately and the serum was stored at -20 degrees C until assayed for total T4, free T4, free T3, TSH, prolactin, growth hormone (TRH test), and FSH, LH, testosterone (GnRH test). Haematological parameters and biochemical profiles were also measured.

RESULTS

After TRH administration, both patient groups showed a normal TSH response; however, their free T4 and free T3 secretion was blunted compared to controls. Normal basal PRL levels increased in an exaggerated fashion, whereas, when compared to chronic renal failure patients on chronic haemodialysis, we did not see a paradoxical GH response or a basal GH increase in these 5 patients. GnRH administration in the study groups elicited a normalization in the LH response without an increase in testosterone levels; however, an exaggerated FSH response was found in the polycythaemic patients (low EPO).

CONCLUSIONS

Thus by investigating the role of low endogenous EPO levels in non-anaemic and anaemic patients with high EPO levels, our study suggests that the underlying chronic disease state may be the major contributing factor in the regulation of the hypothalamo-hypophyseal thyroid and gonadal axes, rather than the EPO levels.

Purification and biologic characterization of plasma-derived megakaryocyte growth and development factor

The isolation and cloning of the ligand for the cytokine receptor, Mpl, have been recently described. In this report we present details of the purification of this novel cytokine (megakaryocyte growth and development factor [MGDF]) from aplastic canine plasma. Two forms of canine MGDF, with apparent molecular weights of 25 kD and 31 kD and sharing a common N-terminal amino acid sequence, were isolated. The sole contaminant detected in purified 25-kD or 31-kD MGDF was canine Ig. Canine MGDF is characterized as a human megakaryocyte colony-stimulating factor that acts synergistically with human recombinant stem cell factor but not interleukin-3. MGDF also appears to be physiologically regulated in response to platelet demand. In canine and murine models, serum levels of MGDF activity peak during the thrombocytopenic periods after irradiation, 5-fluorouracil, or antiplatelet antisera injections. These data indicate that the megakaryocyte-stimulating activity that accumulates in plasma in response to platelet losses is a novel cytokine that functions through an interaction with the Mpl cytokine receptor.

G2 radiosensitivity of cells derived from cancer-prone individuals

The potential of enhanced chromatid damage, observed after X-irradiation of G2 phase, has been used to detect individuals genetically predisposed to cancer, utilising fibroblast/lymphocytes from these patients as well as fibroblasts derived from human tumours. Fibroblasts and/or lymphocyte samples of two autosomal recessive syndromes (xeroderma pigmentosum (XP), Fanconi's anaemia (FA)) and one congenital or acquired disorder, aplastic anaemia (AA), were employed for the G2 radiosensitivity assay. In addition, we have estimated the frequencies of spontaneously occurring chromosomal aberrations as well as G2 radiosensitivity of eight samples of fibroblasts/fibroblast-like cells (two normal, two colorectal carcinoma, two Wilms' tumour, one retinoblastoma and one polyposis coli), and three samples of lymphocytes (two normal and one from a lymphoma patient). The results obtained indicate that there were no differences between fibroblast cells derived from patients or tumours, except FA patients, in the frequency of spontaneously occurring chromosomal aberrations when compared to normal cells. Following X-irradiation we did not observe any significantly increased G2 radiosensitivity in FA and XP cells. Lymphocytes from AA and lymphoma patients, and all tumour cell lines except retinoblastoma, responded with increased frequencies of aberrations following G2 X-irradiation in comparison to cells derived from normal individuals. In our hands, the G2 sensitivity assay could not always discriminate cells from cancer-prone individuals from those of controls.

Growth in patients after allogeneic bone marrow transplant for hematological diseases in childhood

The growth of 66 long-term survivors, transplanted in two centres (Genoa S. Martino and Monza) is reported. Patients were all under age 15 at the time of bone marrow transplantation (mean 9.8 +/- 3.4 years; range 1.07-15 years) with a minimum follow-up of at least 12 months. They were divided into four groups. Group 1: eight patients with severe aplastic anemia (SAA): conditioning included cyclophosphamide (CY) 200 mg/kg only. Group 2: 32 patients with acute lymphoblastic leukemia (ALL), and acute myeloid leukemia (AML): conditioning included CY 120 mg/kg and 10-12 Gy fractionated total body irradiation (fTBI). Group 3: 20 patients with ALL, who had previously received cranial irradiation; conditioning included CY 120 mg/kg and fTBI with an additional testicular irradiation (4 Gy). Group 4: six patients with chronic myeloid leukemia (CML) and AML; conditioning included CY 200 mg/kg and busulfan (BU) 16 mg/kg. Group was impaired in all four groups, including the unirradiated groups (-0.2 +/- 0.7 and -0.5 +/- 0.6 delta-SDS in groups I and 4, respectively). Growth impairment-SDS was statistically significant in the two irradiated groups (-0.7 +/- 1.0 and -0.9 +/- 1.0 delta-SDS in groups 2 and 3, respectively), more marked in patients who had had previous cranial irradiation. Chronic graft-versus-host disease and its treatment were not found to have a major effect on growth.

Longitudinal study of adrenocortical function following allogeneic bone marrow transplantation in children

Basal serum concentrations of cortisol, dehydroepiandrosterone (DHA) and its sulfate (DHAS), 4-androstene-3,17-dione (A4) and 17 alpha-hydroxyprogesterone (17OHP) were measured yearly in children treated with bone marrow transplantation (BMT) with or without preceding total body irradiation (TBI). Age-matched controls were used for comparison. ACTH stimulation tests were performed in the patients before and after treatment. However, in the samples taken before BMT only cortisol was measured. Basal posttreatment cortisol levels were subnormal in TBI-treated boys (n = 14, aged 5-17 years at BMT) during the adrenarcheal period (7-14 years) but became normal afterwards. All other groups had normal cortisol values. Treatment neither affected basal levels nor the ACTH-induced increment (delta-value) of cortisol. In the boys treated with TBI, normal basal levels of 17OHP and adrenal androgens were found with the exception of decreased DHA levels in the postadrenarcheal boys. However, the delta-17OHP values and had an abnormal age relation and were significantly higher than in the patients not treated with TBI. In the patients not treated with TBI (6 boys aged 2-17 years) normal responses were found for 5 years or more after treatment. In female patients treated with TBI (n = 12, aged 1-16 years) circulating levels of DHA, DHAS and A4 were significantly decreased up to 5 years or more following treatment. It is concluded that after TBI, the cortisol homeostasis is maintained at the cost of reduced adrenal androgen secretion.

Normal granulocyte function but impaired monocyte function in a patient with aplastic anemia

Granulocytopenia is an invariable finding in aplastic anemia (AA) and bacterial infections are a frequent complication and major cause of death in patients suffering from this bone marrow disorder. Using well-established assays, we determined the chemotaxis of granulocytes and monocytes as well as the phagocytic capacity of monocytes and oxidative metabolism of granulocytes in a patient with aplastic anemia of unknown etiology. Our results indicate a normal granulocyte oxidative metabolism and granulocyte chemotaxis towards formyl-leucyl-methionyl-phenylalanine (fMLP), whereas monocyte chemotaxis and phagocytic capacity were markedly reduced in this patient.

[Evaluation of bone marrow by opposed phase T1-weighted images and enhanced MR imaging]

We investigated bone marrow in a control group, cases of aplastic anemia and post-irradiation patients by examining T1-weighted (T1WI), short TI inversion recovery (STIR), opposed phase T1WI (op-T1WI) and Gd-DTPA enhanced op-T1WI images obtained by 0.5T MRI. Bone marrow was classified into four types based on MR findings. Normal marrow showed low intensity on op-T1WI and STIR images without enhancement (I). Fatty marrow, which showed high intensity on T1WI and op-T1WI images was observed in aplastic anemia and post-irradiation patients (II). Hematopoietic marrow (III) showed low intensity on op-T1WI and enhanced, while active hematopoietic marrow (IV) revealed high intensity on both STIR and op-T1WI images and was enhanced following Gd-DTPA infusion. Aplastic anemia of moderate grade included types II, III and IV. Enhanced MR was needed to differentiate between types I and III since both types showed low intensity on op-T1WI images. Furthermore, type IV was considered as hyperplastic compared with type III. Enhanced MR and op-T1WI images were useful in evaluating hematopoiesis of bone marrow.

Aplastic anemia and pure red cell aplasia

The role of known hematopoietic growth factors in the pathogenesis of aplastic anemia and congenital hypoplastic anemia has been extensively studied and no evidence has been obtained that deficiency of these factors contributes to the hypoproliferative state in these disorders. Clonal hematopoiesis seems to be present at least in a small percentage of cases of aplastic anemia, a finding that needs further investigation. Androgens were shown to be beneficial only for women with aplastic anemia treated with antilymphocyte globulin. Unrelated-donor bone marrow transplantation is becoming a realistic approach for children and very young adults with aplastic anemia, but in older groups the survival is very poor. New observations on abnormalities of lymphokines and cytokines in Fanconi's anemia have been described, but their pathogenetic significance remains unknown. A large number of studies have excluded the possibility that abnormalities of c-kit/SCF genes and their expression are responsible for the erythroid aplasia in Diamond-Blackfan syndrome. Cyclosporine was found to be an effective treatment for pure red cell aplasia associated with chronic lymphocytic leukemia. The cell membrane receptor for B19 parvovirus has been identified as the P antigen. Long-term studies showed that in 20% of patients with homozygous sickle cell disease, infection by B19 does not cause erythroid aplasia.

Marrow transplant experience for children with severe aplastic anemia

PURPOSE

The two major factors associated with lack of survival after allogeneic marrow transplant for severe aplastic anemia have been graft rejection and acute graft versus host disease (GVHD). As a result, survival for patients transplanted in the 1970s was approximately 68%. Improved survival during the 1980s was primarily related to the decrease in the incidence of acute GVHD with the use of combination methotrexate and cyclosporine for GVHD prophylaxis. Although the incidence of graft rejection has not changed, the time to graft rejection has been delayed.

PATIENTS AND METHODS

One hundred forty children < 18 years of age received a marrow transplant for severe aplastic anemia at the Fred Hutchinson Cancer Research Center between May, 1971 and June, 1991. Four recipients of syngeneic marrow received a simple marrow infusion, 119 recipients of HLA-identical family member marrow received cyclophosphamide (CY), 200 mg/kg; most recipients of alternative donor marrow received CY plus 12.0 Gy fractionated total body irradiation. GVHD prophylaxis was MTX only for 91 recipients of HLA-identical family member marrow, and was MTX plus CSP for all other allogeneic marrow patients. Estimates of graft rejection, acute and chronic GVHD, survival and event-free survival (EFS) were determined by the Kaplan-Meier method.

RESULTS

Two recipients of syngeneic marrow achieved engraftment with donor marrow infusion only and two required immunosuppression with CY. Among the 119 recipients of HLA-identical family member marrow the type of GVHD prophylaxis did not influence graft rejection but non-transfused patients had 10% incidence of rejection compared to 22% for transfused patients (p = 0.1). All patients with late graft rejection survive whereas those with early rejection usually do not. The incidence of acute GVHD was 27% and 11% for MTX recipients and MTX plus CSP recipients, respectively (p = 0.11), and the probability of chronic GVHD was 30% and 26%, respectively. Survival is 64% for recipients of MTX and 96% for recipients of MTX plus CSP (p = 0.007), but EFS was 60% and 71%, respectively (p = 0.48). Recipients of partially matched family member or unrelated marrow donor grafts have transplants complicated by infections and GVHD. Growth and development of CY only recipients is normal and several children have been born to these former patients.

CONCLUSIONS

High dose CY is usually an effective preparative regimen for children with severe aplastic anemia and an HLA-identical family member marrow donor. Additional immunosuppression with anti-thymocyte globulin may result in a further decrease in graft rejection and improved EFS. Identification of a group of children who are unlikely to respond to immunosuppressive treatment could permit earlier transplantation for patients without HLA-identical family member donors available. Children who receive CY only have normal growth and development.

Thyroid function in children after allogeneic bone marrow transplantation

Thyroid function was investigated in 35 children after allogeneic BMT. The study was longitudinal and all patients were followed for at least 5 years. Once a year TSH, T4, T3 and the TRH test were performed. Patients with severe aplastic anemia (n = 6) were transplanted without total body irradiation (TBI) and they had no detectable alterations in thyroid function. Patients with leukemia (n = 27) were conditioned with 10 Gy TBI in one fraction. The accumulated frequencies of thyroid dysfunction were 3 of 27 (11%) with high TSH and low T3 or T4 levels, and 10 of 27 (37%) with high basal TSH and normal T3 and T4 levels. An additional 11 of 27 (41%) had an exaggerated TSH response in the TRH test and normal basal TSH and T3/T4 levels. Only 3 of 27 (11%) continued to have normal values. Treatment with levo-thyroxine (L-T4) was given to the patients with a high basal TSH level. As 24 of 27 (89%) children had signs of disturbance in the thyroid axis, prophylactic L-T4 treatment for a few years after BMT with TBI may be of value. The main cause of a change in thyroid function after BMT seems to be conditioning with TBI.

Chronic radiation-induced alteration in hematopoietic repair during preclinical phases of aplastic anemia and myeloproliferative disease: assessing unscheduled DNA synthesis responses

Protracted, low-daily-dose gamma-ray exposure (3.8-7.5 cGy/day) segregates canines into separate survival- and pathology-based subgroups by the early elicitation of distinct, repair-mediated hemopathological response pathways. In this study, we verified the blood and marrow responses of two major subgroups prone to either aplastic anemia or myeloproliferative disease, along with two variants, and extended our analyses of hematopoietic repair to include studies of DNA repair in bone marrow blasts using an autoradiographically based unscheduled DNA synthesis (UDS) assay. The myeloproliferative disease-prone subgroup exhibited extended survival (> 200 days), related to partial, gradual restoration of blood leukocyte, platelet, and marrow progenitor levels following an initial phase of acute suppression. Marrow blasts taken during the restoration phase showed expanded and qualitatively modified UDS relative to marrow blasts of age-matched control animals. The amount of UDS per blast (signal strength) increased significantly, as did the number of UDS-positive cells and their sensitivities to high-dose UV induction and 1-beta-D-arabinofuranosylcytosine chemical inhibition. A nonevolving myeloproliferative disease-prone variant having prolonged survival (> 200 days) and restored blood cells and marrow progenitor levels also had marrow blasts with expanded UDS responses, but these were uniquely evoked by low (but not high) doses of UV inducer. The aplastic anemia-prone subgroup was characterized by short survival (< 200 days), progressive decline (without restoration) in all measured blood and marrow compartments, and largely nonsignificant changes in UDS responses of marrow blasts. A variant of this aplastic anemia-prone subgroup (with comparable short survival due to markedly ineffective hematopoiesis, but expressing select preleukemic features) exhibited reduced numbers (relative to age-matched controls) of highly responsive, UDS-positive marrow blasts (in terms of UDS signal strength and increased to sensitivity 1-beta-D-arabinofuranosylcytosine-induced UDS inhibition). From these observations we conclude that: (a) the UDS response of marrow blasts, a correlate of hematopoietic progenitorial repair, is altered differentially within selected subgroups of animals under chronic radiation exposure; and (b) the nature of altered UDS repair response patterns appears to be largely related to the preclinical status/predisposition of the individual animal and thus may provide prognostically useful information in the clinical monitoring of chronically irradiated individuals with minimal but evolving hematological disease.

[Enhanced osteogenesis in severe aplastic anemia]

Histologic specimens of the bone marrow were obtained from healthy subjects and aplastic anemia (AA) ones. Comparison of the histomorphometry was indicative of an increase in spongy bone tissue and in the number of osteoid cells in AA. This indirectly suggested enhanced proliferative activity of osteogenic precursors and osteosynthesis in AA. Interrelationship is probable between osteogenesis and hemopoiesis.

[Abnormalities in regulation system of granulopoiesis]

We studied the effects of several cytokines on the development of granulocyte-macrophage (GM) progenitors using the serum-deprived culture. SCF plays an important role in the GM-CSF- or IL-3-dependent production of neutrophils and macrophages. In vitro colony assay also suggests an increase in sensitivity of GM progenitors to cytokines (GM-CSF, IL-3, G-CSF and/or SCF) in a patient with juvenile chronic myelogenous leukemia. A high level of serum IFN-gamma was associated with leukopenia and thrombocytopenia in a patient with hemophagocytic syndrome. Based on the evidence that IFN-gamma significantly inhibited the proliferation of GM progenitors, IFN-gamma-mediated suppression was suggested as one of the mechanisms causing cytopenia. In patients with aplastic anemia and neutropenia, an increase of serum G-CSF levels was observed when neutrophils decreased remarkably in number. However, the serum SCF levels were constant in these patients. A failure of SCF to enhance colony growth in some patients with aplastic anemia implies qualitative abnormalities of hematopoietic progenitors.

Clonal haematopoiesis in children with acquired aplastic anaemia

The methylation pattern of three X-linked genes, phosphoglycerate kinase (PGK), hypoxanthine phosphoribosyl transferase (HPRT) and DXS255 detected by hypervariable M27 beta probe, was analysed to determine the proportion of aplastic anaemia (AA) with clonal haematopoiesis in Japanese children. Methylation analysis was performed on DNA from separated granulocytes and compared to that of bone marrow derived fibroblasts to exclude selective lyonization in all somatic cells. Of 20 female patients examined, the methylation pattern of at least one gene was informative in granulocyte DNA from 18 patients (90%). Of these, 8/20 patients (40%) were heterozygous for PGK, 8/18 (44%) were heterozygous for HPRT and 17/18 (94%) were heterozygous for DXS255. In 14/18 patients both alleles were equally methylated. Four patients exhibited a unilateral methylation pattern in their granulocytes. The same unilateral pattern was again demonstrated in fibroblasts from two of the four patients suggesting that in the latter one X chromosome was selectively inactivated in all of the somatic cells. The remaining two patients showed a unilateral methylation pattern that was restricted to their granulocytes, suggesting the existence of true clonal haematopoiesis. They responded well to antilymphocyte globulin (ALG) and presently have no evidence of a clonal disorder such as myelodysplastic syndrome (MDS) or paroxysmal nocturnal haemoglobinuria (PNH). Although these results indicate that some children with AA exhibit clonal haematopoiesis, analysis of a greater number of subjects will be required to establish the clinical value of clonal haematopoiesis in patients with AA.

[Ferrokinetics and bone marrow scanning in patients with myelodysplastic syndrome, hypoplastic myelodysplastic syndrome and aplastic anemia]

Ferrokinetic measurement were performed in a total of 48 patients with myelodysplastic syndrome (MDS), 13 with hypoplastic MDS and 25 with aplastic anemia (AA). Forty seven % of patients with hypoplastic MDS progressed to acute leukemia, however none of the patients with AA progressed to acute leukemia. Sixty-nine% of the patients with MDS showed increased erythron transferrin uptake (ETU) caused by ineffective erythropoiesis. On the other hand, 85% of the patients with hypoplastic MDS and all patients with AA showed decreased ETU caused by reduced erythropoiesis. Positive correlation was observed between ETU and the erythroid precursor cells in the bone marrow. Bone marrow scintigraphy utilizing 99mTc-sulphur colloid showed peripheral expansion of active marrow in MDS patients and islands-like distribution in hypoplastic MDS and AA patients. Ferrokinetics and bone marrow scintigraphy demonstrated the difference between typical MDS and hypoplastic MDS. Hypoplastic MDS appears to be a distinct clinicopathologic entity.

[The pathophysiology of aplastic anemia]

It is the conventional opinion that acquired aplastic anaemia is a heterogeneous disease including basically different conditions, such as idiopathic or virus induced pancytopenia, toxic-allergic marrow damage or autoimmunity. Here, an alternative concept is proposed, according to which aplastic anaemia is one disease, but multifactorial in all patients, apparent differences being due to the relative prevalence of one or the other pathological component in individual patients. Bone marrow from patients in the severe phase of aplastic anaemia does not grow in culture and is therefore not suitable for experimentation. Alternatively, bone marrow from patients who have resumed some degree of autologous bone marrow function, but still have residual signs of the disease after non-invasive therapy, offers the possibility to study pathological mechanisms in vitro. The majority of experiments presented have been done in such patients, assuming that their status of disease in some way reflects the original, more serious pretreatment condition. Three major pathophysiological components will be discussed, and it will be proposed how these factors act in concert to cause or aggravate aplasia.

Increased respiratory burst activity of neutrophils in patients with aplastic anemia: effects of granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor

The superoxide (O2-)-releasing capacity in response to N-formyl-methionyl-leucyl-phenylalanine (FMLP) and the priming effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF) and granulocyte-macrophage colony-stimulating factor (rhGM-CSF) on FMLP-induced O2-release were investigated in neutrophils from 13 patients with aplastic anemia (AA). The O2(-)-releasing capacity of AA neutrophils (0.85 +/- 0.36 nmol/5 min/1 x 10(5) cells, n = 13) was significantly (p < 0.01) increased as compared with that of normal neutrophils (0.24 +/- 0.12 nmol/5 min/1 x 10(5) cells, n = 17). There was no close relationship between the O2(-)-releasing capacity and the peripheral blood neutrophil count or the plasma concentration of C-reactive protein. The plasma concentrations of G-CSF and GM-CSF were not elevated to the detectable levels (< 0.1 ng/ml and < 0.2 ng/ml, respectively) in all patients tested. FMLP-induced O2(-)-release was further enhanced by pretreatment of cells with rhG-CSF or rhGM-CSF for 10 min at 37 degrees C, except that no significant priming by rhG-CSF was observed in five patients. The priming effect of rhGM-CSF was consistently greater than that of rhG-CSF in all patients. The i.v. administration of rhGM-CSF (6 micrograms/kg body weight/day) to one patient resulted in an increase in neutrophil O2(-)-release stimulated by FMLP. These findings indicate that neutrophils from AA patients are already primed in vivo for enhanced release of O2- and that these neutrophil functions are further potentiated by rhG-CSF or rhGM-CSF.

[Advances in the treatment of aplastic anemia]

The purpose of this paper is to describe the current advances in the pathogenesis, classification and treatment of acquired aplastic anemia (AA). The therapeutical experience obtained at the Servicio de Hematología, Centro Medico Nacional, Siglo XXI is described. Bone marrow transplantation is the first choice therapy for severe AA. This procedure succeeds in obtaining complete remission in nearly 80% of the cases. Nevertheless, few patients are eligible for such therapy, consequently other treatments should be considered. In this context some immunosuppressive therapies such as antilymphocyte globulin had shown to produce favorable responses in 60% of the patients. In addition, androgens and immunosuppressive drugs like methylprednisolone bolus and cyclosporin A do not have a definitive place in severe AA. Finally, it is important to describe the experience with lymphocytapheresis, a new procedure, that decreases the immunological response against the normal hematopoiesis by removing the population of T-lymphocytes inducing complete remission in a few patients.

Change of thyroid function in 50 patients with aplastic anemia

The serum thyroid hormones were measured in 50 patients with aplastic anemia (AA). Serum T3 and T4 levels were significantly lower, especially in the elderly and in those in chronic AA, while they were normal in acute AA. There was no obvious difference with thyroid-stimulating hormone (TSH). It was suggested that the result may be caused by euthyroid sick syndrome, a protective adaptation that helps in classifying and evaluating the prognosis of the disease.

The pathophysiology of aplastic anemia

No single cause can explain aplastic anemia. Two major factors are involved: An intrinsic derangement of hemopoietic proliferation capacity that is essentially compatible with life, but has to be considered a premalignant condition. This primarily diseased tissue can be destroyed by immune mechanisms in an attempt to achieve self-cure. Therefore, immunosuppressive therapy can mitigate this immune reaction but leaves the patient with a poorly proliferating bone marrow that is prone to late complications. The clinical presentation and course depend on the balance of these two major factors: If the immune reaction is strong, acute severe aplasia occurs, whereas in patients with a weak immune reaction the disease will present itself rather as chronic pancytopenia with myelodysplastic traits. Co-involvement of environmental cells in the disease process is an additional factor. Poor production of hemopoietic growth factors may aggravate aplasia and poor immune competence may allow abnormal clones to proliferate. All these pathophysiological factors are genetically determined.

Response of CFU-GM to increasing doses of rhGM-CSF in patients with aplastic anemia

The aim of this study was to test whether large amounts of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) are capable of promoting the growth of hemopoietic progenitors from patients with marrow failure. For this purpose 0.1, 100, 1000, 10,000 and 20,000 ng/ml of rhGM-CSF were added to 10(5) light-density (adherent cell-depleted) bone marrow cells from 9 normal controls and from 52 patients with aplastic anemia, 25 cases of which were transfusion-dependent (Tx-D) aplastic anemia (AA) and 27 of which were transfusion-independent (Tx-I) aplastic anemia (AA). A dose-dependent increase of granulocyte-macrophage colony-forming units (CFU-GM) was observed in healthy donors, from 81 to 247 colonies at 0.1 and 1000 ng/ml of rhGM-CSF, with a plateau thereafter. Tx-I AA patients showed the best increase of CFU-GM in response to colony-stimulating factor, from 0.1 to 32.7 mean colonies at 0.1 and 20,000 ng/ml of rhGM-CSF, and the increment was greater when compared to controls. The ratio of CFU-GM grown from these patients and controls was 1:810 at 0.1 ng/ml of rhGM-CSF and 1:7.9 at 20,000 ng/ml. Eleven patients were studied at diagnosis; there was no in vitro response to rhGM-CSF (0 and 1.8 mean colonies/10(5) cells at 0.1 and 10,000 ng/ml). Overall, Tx-D AA patients showed minimal increments of CFU-GM growth at very high doses of rhGM-CSF. Two suggestions come from this study: 1) maturation of CFU-GM from recovering AA patients appears to require larger doses of GM-CSF than normal controls, and 2) very high doses of rhGM-CSF have little or no effect on CFU-GM growth in AA patients. This may be relevant for clinical studies designed to improve hemopoiesis in patients with marrow failure.

In vitro assessment of marrow 'stem cell' and stromal cell function in aplastic anaemia

An in vitro model system is described that allows separate assessment of 'stem cell' and stromal cell function in aplastic anaemia (AA). Seven patients with non-severe AA, who had responded to immunosuppressive therapy and had haematological evidence of residual marrow function, were studied. Of these, three with otherwise typical AA had an acquired clonal cytogenetic marker. Purified bone marrow haemopoietic progenitors labelled with CD34 monoclonal antibody were positively selected using the fluorescence activated cell sorter (FACS) from both normal subjects and from patients with AA. The generative capacity of the CD34 positive cells was assessed by monitoring the output of granulocyte/macrophage colony forming cells (CFU-GM) in the non-adherent layer after inoculation onto irradiated performed long-term marrow culture (LTBMC) stromas. Stromal function in AA was assessed by inoculating CD34 positive cells from normal bone marrow onto performed irradiated stromas from patients with AA. Haemopoietic cell ('stem cell') function in AA was assessed by inoculating CD34 positive cells from AA patients onto confluent irradiated normal marrow stromas. Using these crossover/LTBMC experiments, all patients exhibited severe defects in haemopoietic cell function with normal functioning stroma. The proportion of CD34 positive cells present in bone marrow from these patients was reduced compared with controls, they comprised fewer small primitive 'blast-like' cells which in normal bone marrow are known to possess marrow repopulating ability, and demonstrated reduced clonogenic potential in short-term colony assays.

Aplastic anemia: current concepts and dental management

Aplastic anemia (AA) is a rare blood dyscrasia in which the peripheral blood cells are decreased because of bone marrow failure. The clinical course reflects the severity of pancytopenia and is unpredictable for the individual. Hemorrhage and infection remain the major threats to these patients. Recent advances in transfusion medicine, infection management, bone marrow transplantation, and immunosuppressive therapy have improved survival of patients with AA. Oral manifestations of AA are common and may have serious sequelae. Two cases of acute periodontal infection associated with AA are presented. Dental management guidelines are presented in the context of interdisciplinary care.

The hematopoietic defect in aplastic anemia assessed by long-term marrow culture

Thirty-two patients with aplastic anemia (AA) have been studied using the long-term bone marrow culture (LTBMC) system. Of these patients, 26 had been treated with immunosuppressive therapy including antilymphocyte globulin (ALG) with or without androgens or high-dose methyl prednisolone. The remaining six patients either required no treatment or were studied before therapy was begun. Thirty-one of 32 patients (96%) had defective hematopoiesis in LTBMC with little or no evidence for the generation of primitive progenitor cells. The only exception was a patient with spontaneous recovery of aplasia in whom the defect was less marked. Crossover LTBMC experiments were performed in 23 cases by inoculating (1) patient marrow hematopoietic cells that had been depleted of adherent cells onto preformed, irradiated, normal stromas to assess the proliferative capacity of the hematopoietic cells, and (2) normal marrow hematopoietic cells that were depleted of adherent cells onto preformed, irradiated stromas from patients with AA to assess stromal function. Results of these experiments demonstrated a hematopoietic defect in all patients that was independent of the degree of hematologic recovery after ALG therapy. Only one patient had a probable stromal defect and this coexisted with a defect in the regenerative capacity of hematopoietic cells. We conclude that LTBMC is a sensitive method for detecting and defining the hematopoietic failure in AA. We suggest that the defective hematopoiesis present in all patients studied may be important in the pathogenesis of clonal evolution in AA.

The changes of BPA level in 31 cases of children with aplastic anaemia and its clinical significance

Burst-promoting activity (BPA) was measured in the sera from 31 children with aplastic anaemia (AA). BPA levels were elevated in most of the children with AA (65.2%), the mean value (137.7 +/- 18.4%) being significantly higher than that in normal children (69.6 +/- 9.4%), in children in the recovery period and in children with non-aplastic anaemia. There was a negative relationship between the BPA level in children with AA and the peripheral haemoglobin concentration. The BPA level was higher in those whose duration of illness was shorter than 1 year. In three cases of AA caused by chloramphenicol and benzene hexachloride and one case of congenital pure red cell AA, the BPA level was not elevated. Eleven patients received fetal liver cell suspensions intravenously (FLI). After FLI the BPA level in their sera was significantly reduced. According to these results, it appears that the elevation of BPA level is a special phenomenon of AA. The measurement of BPA in serum is helpful for differentiation between AA and other kinds of anaemia. The elevation of the BPA level in serum is a biological compensation for the haematopoietic disorder, and the measurement of BPA in the serum of patients with AA may be helpful in evaluating the haematopoietic condition.

Thyroid function tests in patients undergoing bone marrow transplantation

Thyroid function was studied prospectively in 27 patients receiving bone marrow transplants to determine the effect of this procedure and its sequelae on serum thyroid hormone levels and thyrotropin secretion. Serum triiodothyronine and free triiodothyronine concentrations declined to subnormal levels in nearly all of the patients; free thyroxine concentration became subnormal in 15 patients. At the time of the nadir of the serum T3 concentration, serum thyrotropin concentration, measured by a sensitive immunoradiometric assay, declined significantly and became subnormal in nine patients. The data suggest that the reduction of serum thyroxine levels after transplantation is attributable, at least in part, to inhibition of thyrotropin secretion.

Pathophysiology of aplastic anaemia

It is the conventional opinion that acquired aplastic anaemia is a heterogenous disease including basically different conditions, such as idiopathic or virus induced pancytopenia, toxic-allergic marrow damage or autoimmunity. Here, an alternative concept is proposed, according to which aplastic anaemia is one disease, but multifactorial in all patients, apparent differences being due to the relative prevalence of one or the other pathophysiological component in individual patients. Bone marrow from patients in the severe phase of aplastic anaemia does not grow in culture and is therefore not suitable for experimentation. Alternatively, bone marrow from patients who have resumed some degree of autologous bone marrow function, but still have residual signs of the disease after non-invasive therapy, offers the possibility to study pathophysiological mechanisms in vitro. The majority of experiments presented in this chapter have been done in such patients, assuming that their status of disease in some way reflects the original, more serious pretreatment condition. Three major pathophysiological components will be discussed, and it will be proposed how these factors act in concert to cause or aggravate aplasia.

[Effect of humoral factors produced by lymphocytes on hematopoietic progenitor cells--productive ability of colony stimulating activities and interferon-gamma by blood mononuclear cells in patients with aplastic anemia]

To evaluate the role of cytokines in patients with aplastic anemia, colony stimulating activities (CSA) and interferon-gamma (IFN-gamma) in cultured media of lymphocytes with phytohemagglutinin (PHA-LCM) were measured with methylcellulose culture method in 20 patients (age 3 to 69 years). The CSA for granulocyte/macrophage (GM-CSA) in patients was equivalent to that of normal donors, while low burst promoting activity (BPA) was observed in PHA-LCM from 7 adult patients (61 +/- 17%). The ability of BPA production varied widely in 13 children (97 +/- 37%). In some patients, low production of BPA improved after successful treatment of antilymphocyte globulin. The IFN-gamma in PHA-LCM disclosed no significant difference between patients and normal donors. From these results, low production of BPA may have a role in the development of AA in certain patients. It is also suggested that therapy with recombinant cytokines such as GM-CSF and IL-3, detected as BPA in our culture system, could be effective for those patients.