Granulocytic progenitor cells in aplastic anaemia

Foetal liver infusion in a chronic myeloid leukemia patient with busulphan toxicity

A 36-year-old man suffering from chronic myeloid leukemia (in chronic phase) was initially treated with busulphan. At the end of 6 months of follow-up he developed bone marrow aplasia. He was given single foetal liver infusion therapy. The patient recovered fully from aplasia. He continued in chronic phase for more than 7 years with intermittent busulphan therapy.

The Assessment of the Hematopoietic Reservoir After Immunosuppressive Therapy or Bone Marrow Transplantation in Severe Aplastic Anemia

We investigated the hematopoietic reservoir in 43 severe aplastic anemia (SAA) patients following immunosuppression (IS) (n = 15) or bone marrow transplantation (BMT) (n = 28), at a median interval of 5 years (range, 2-20) from treatment. All patients had normal blood counts, good marrow cellularity, and normal numbers of colony forming unit-granulocyte macrophages (CFU-GM). Burst forming unit-erythroid (BFU-E) and colony forming unit-granulocyte erythroid megakaryocyte macrophages (CFU-GEMM) numbers were reduced when compared with normal controls. However, the most pronounced defect was observed at the level of long-term culture-initiating cells (LTC-IC), which significantly differed from controls (P < .00001) both for IS and BMT patients. Their number did not improve with time and was not affected by transplant or treatment-related variables. When IS patients were compared with BMT we found comparable numbers of CFU-GEMM (P = .8) and LTC-IC (P = .9), but lower numbers of BFU-E and CFU-GM (P = .05 and P = .004, respectively), suggestive of a persistent suppressive mechanism. These data indicate that LTC-IC numbers are severely reduced in BMT and IS patients, contradicting the common belief that the former are fully reconstituted as compared with the latter. In addition, the number of mature cells and committed progenitors does not seem to reflect the real size of the hematopoietic reservoir and few stem cells may be sufficient to guarantee normal hematopoiesis long term.

The Assessment of the Hematopoietic Reservoir After Immunosuppressive Therapy or Bone Marrow Transplantation in Severe Aplastic Anemia

We investigated the hematopoietic reservoir in 43 severe aplastic anemia (SAA) patients following immunosuppression (IS) (n = 15) or bone marrow transplantation (BMT) (n = 28), at a median interval of 5 years (range, 2-20) from treatment. All patients had normal blood counts, good marrow cellularity, and normal numbers of colony forming unit-granulocyte macrophages (CFU-GM). Burst forming unit-erythroid (BFU-E) and colony forming unit-granulocyte erythroid megakaryocyte macrophages (CFU-GEMM) numbers were reduced when compared with normal controls. However, the most pronounced defect was observed at the level of long-term culture-initiating cells (LTC-IC), which significantly differed from controls (P < .00001) both for IS and BMT patients. Their number did not improve with time and was not affected by transplant or treatment-related variables. When IS patients were compared with BMT we found comparable numbers of CFU-GEMM (P = .8) and LTC-IC (P = .9), but lower numbers of BFU-E and CFU-GM (P = .05 and P = .004, respectively), suggestive of a persistent suppressive mechanism. These data indicate that LTC-IC numbers are severely reduced in BMT and IS patients, contradicting the common belief that the former are fully reconstituted as compared with the latter. In addition, the number of mature cells and committed progenitors does not seem to reflect the real size of the hematopoietic reservoir and few stem cells may be sufficient to guarantee normal hematopoiesis long term.

Thrombopoietin serum levels in patients with aplastic anaemia: correlation with platelet count and persistent elevation in remission

In an attempt to evaluate the role of thrombopoietin (TPO) in the pathobiology of aplastic anaemia (AA), we have examined TPO levels in sera from 54 AA patients and 119 healthy controls. A total of 92 samples were collected from AA patients: 43 samples were harvested at diagnosis, 23 samples in the cytopenic period after treatment, and 26 samples when patients were in partial (n=10) or complete remission (n=16) following immunosuppressive treatment. TPO serum levels were assessed by a sandwich-antibody ELISA that utilized a polyclonal rabbit antiserum for both capture and signal. Serum samples from normal donors revealed a mean TPO level of 95.3 +/- 54.0 pg/ml (standard deviation). Mean TPO levels in AA sera collected at diagnosis and before onset of treatment were 2728 +/- 1074 pg/ml (P<0.001 compared to normal controls: mean platelet count at that time: 27x10(9)/l). TPO serum levels of AA patients in partial or complete remission after immunosuppressive treatment were significantly lower than TPO levels at diagnosis (P<0.001). However, despite normal platelet counts (mean 167x10(9)/l), TPO levels remained significantly elevated in complete remission (mean TPO 1009 +/- 590 pg/ml, P<0.001 compared to normal controls). There was a significant inverse correlation between serum TPO levels and platelet counts in AA patients who were not transfused for at least 2 weeks prior to sample collection (coefficient of correlation (r) = -0.70, P<0.0001). In summary, TPO levels were highly elevated in sera of patients with AA. Thus there is no evidence to suggest an impaired TPO response contributing to thrombocytopenia in AA. Thrombopoietin did not return to normal levels in remission, indicating a persisting haemopoietic defect in remission of AA. We hypothesize that elevated levels of TPO may be required to maintain normal or near normal platelet counts in remission of AA.

Spontaneous cytokine overproduction by peripheral blood mononuclear cells from patients with myelodysplastic syndromes and aplastic anemia

We studied spontaneous cytokine production by peripheral blood mononuclear cells (PBMC) obtained from 14 patients with aplastic anemia (AA) and 28 various myelodysplastic syndromes (MDS). The levels of interleukin-6, interleukin-1 beta, and tumor necrosis factor-alpha in cultured PBMC were measured by ELISA. The average levels of these cytokines were higher in AA or in refractory anemia (RA) than in RA with excess of blasts (RAEB) or in RAEB in transformation (RAEB-T). Marked cytokine overproduction was observed in RA as well as in AA. High cytokine levels were observed in hypocellularity and low blast cell counts in the bone marrow. These results may suggest that the increase of cytokines may be a reactive response in hypocellular bone marrow.

A phase I/II trial of recombinant human interleukin-6 in patients with aplastic anaemia

In a phase I/II study, 11 patients with marrow failure (10 with acquired aplastic anaemia and one with pancytopenic Fanconi anaemia) were treated with recombinant human interleukin-6 (rhIL-6) to assess the safety and tolerability of rhIL-6 and its effects on peripheral blood counts, bleeding complications and transfusion requirements. All patients with acquired aplastic anaemia were refractory to immunosuppressive treatment or had relapsed after immunosuppressive therapy and were not bone marrow transplantation candidates. Recombinant hIL-6 was to be given as a once-daily subcutaneous injection for 28 d at doses ranging from 0.5 to 5.0 micrograms/kg. After an observation period of 2 weeks, five patients received a second treatment course of 28 d. Only one patient had a sustained increase in platelet count from 18,000 to 72,000/microliters. Bleeding occurred in four patients and caused premature discontinuation of rhIL-6 therapy in three patients. A deterioration of pre-existing anaemia was observed in nine patients. No significant changes of leucocyte counts were observed during the first cycle. During the second cycle the peripheral blood monocyte counts decreased significantly. No significant changes in bone marrow cellularity were observed. Recombinant hIL-6 induced a dose-dependent increase in acute-phase reactants in all patients. Other adverse events included fever, headache, arthralgia, tachycardia and hypertension. In conclusion, rhIL-6 given alone at low doses does not increase platelet counts in the majority of patients with aplastic anaemia and can precipitate a sudden worsening of pre-existing anaemia and thrombocytopenia. This study was discontinued prematurely on account of the toxicity of rhIL-6 seen in patients with aplastic anaemia.

Serum erythropoietin and serum transferrin receptor levels in aplastic anaemia

Serum erythropoietin (EPO) and soluble transferrin receptor levels were serially measured in 74 patients with aplastic anaemia (AA). As control groups we investigated healthy controls (n = 24) and patients with iron-deficiency (n = 23) or haemolytic anaemia (n = 16). There was a significant negative correlation of log EPO on haematocrit both in AA patients and in the anaemic control group. However, for the same degree of anaemia, log EPO levels in AA were significantly higher than in iron-deficiency or haemolytic anaemia. EPO levels at diagnosis did not correlate with severity of aplastic anaemia, nor did they predict outcome after immunosuppression. During immunosuppressive treatment of AA with anti-thymocyte globulin and cyclosporine A, EPO levels were significantly lower compared with pre-treatment values without a corresponding change in haematocrit. This impaired EPO response to anaemia during immunosuppression might affect recovery of erythropoiesis. In AA patients, EPO levels declined with haemopoietic recovery. However, compared with normal controls, EPO levels in remission patients were still higher with respect to their haematocrit. Results of this study argue against the model of a simple feedback regulation of EPO via hypoxic anaemia. Our data support the hypothesis that cytokines and the erythropoietic progenitor pool are involved in the regulation of EPO production. The results illustrate that serial measurements of EPO along with therapeutic interventions are necessary to identify patients who might benefit from treatment with exogenous recombinant human EPO.

Relapse of aplastic anaemia after immunosuppressive treatment: a report from the European Bone Marrow Transplantation Group SAA Working Party

This study was designed to determine the incidence of relapse and factors predictive for relapse in 719 patients with severe aplastic anaemia (SAA) after immunosuppressive treatment (IS). Patients developing myelodysplasia or acute leukaemia after IS, and patients receiving a transplant, were excluded from this analysis. Response was defined as reaching complete independence from transfusions, relapse was defined as becoming again transfusion dependent. This criteria was validated by similar figures when using other 'relapse criteria' such as drop in neutrophil or platelet counts. Of 358 patients responding to IS. 74 patients relapsed after a mean time of 778 d after treatment. The actuarial incidence of relapse is 35.2% at 14 years after IS. The risk for relapse was higher in patients responding within 120 d from IS (48%) compared to patients responding between 120 and 360 d (40%) and only 20% for slow responders (> 360 d from IS) (P < 0.00001). In multivariate analysis this factor still proved significant (P < 0.0001). The mean time between diagnosis and treatment was significantly longer in patients relapsing compared to patients who did not relapse (260 v 134 d, P = 0.037). Relapse was not predicted by the severity of the disease, age, and sex. In 39 of the 74 relapsing patients a second response could be achieved. Responses after relapse were associated in univariate analysis with early response to previous IS and early occurrence of relapse. The actuarial survival of patients not relapsing is significantly better than survival of patients relapsing (79.8% v 67.1%, P = 0.0024). However, the actuarial survival of 39 relapsing patients who responded again to IS was similar to patients not relapsing (86%) and significantly better than in 35 patients not reaching a second response after relapse (49.3%, P = 0.0015). This study indicates that relapse is a relevant problem in the treatment of aplastic anaemia, and does have an impact on overall survival. Prospective studies of immunosuppressive regimens, looking at responses, should also address this problem in the future.

In vitro revelations of aplastic anemia

Aplastic anemia (AA) is a most difficult disease to study in vitro. By the time the disease presents, the marrow is already hypocellular and the peripheral blood shows pancytopenia, leaving little material remaining for study. However, an understanding of its pathogenesis could provide insight into the control of normal hemopoiesis since AA is an in vivo manifestation of failure of normal hemopoiesis and may provide a way of examining stromal cell-stem cell relationships. Recent interest in the pathogenesis of AA has resulted from a) new laboratory techniques, such as stem cell purification used with modifications of the long-term bone marrow culture system and analysis of stem cells at the molecular level with X-linked DNA probes, and b) the availability of recombinant human hemopoietic growth factors (HGF) in large quantities. Consequently, analyses of the function of some of the individual components of stromal cell mediated hemopoiesis in AA patients have been performed. This has been paralleled, and in some instances preceded, by clinical trials of HGF in patients with AA.

Long-term culture of aplastic anaemia bone marrow

Long-term bone marrow cultures (LTBMC) were established with marrow from 11 patients with aplastic anaemia (AA). Bone marrow from five patients, with low numbers of committed progenitor cells, exhibited an increase in committed progenitor cell production to normal levels in the first week of LTBMC. None of 44 haematologically normal marrow cultures showed this increase. Mature and committed progenitor cell production in all cultures from aplastic anaemia bone marrow, declined faster than in normal cultures. This study indicates that short-term culture for committed progenitor cells is an underestimate of the proliferative capacity of bone marrow from some patients with AA. LTBMC may provide a useful system for further studies into the mechanisms responsible for this increased growth in some patients with AA.

Treatment of refractory aplastic anemia with plasmapheresis: report of a case in childhood with review of the literature

Treatment of aplastic anemia may raise considerable problems in some patients. This report concerns a boy whose illness started at 11 years of age. At first admission laboratory data were: hemoglobin 7.5 g/l, and counts of leucocytes, neutrophils and platelets were 2.3, 0.6, and 8 x 10(9)/l, respectively. His bone marrow was hypoplastic with sparse erythropoiesis. The patient did not respond to traditional medical treatment. Serum contained a high concentration of erythropoietin but no antibodies against erythropoietin. The patient's serum did neither alone, nor supported with recombinant erythropoietin, stimulate erythropoiesis in a bioassay, suggesting that some factor(s) inhibiting erythropoietic activity was present. Based on this hypothesis, plasma exchange was performed. After 26 weeks of plasmapheresis the hematological parameters were normalized. We conclude that plasmapheresis might be an alternative in treatment of resistant aplastic anemia. Further diagnostic tools to identify patients who might benefit from such a treatment are required.

New evaluations of circulating granulocyte and macrophage stem cells in healthy adults using conditioned media and recombinant human growth factors

Peripheral human blood contains granulo-monocyte (CFU-GM) and eosinophil (CFU-Eo) progenitors. In vitro, the number of colony forming units is thought to range from 0.1-14 per 2 x 10(5) plated cells. We show that the number of CFU-GM, Eo depends on culture methods. By modifying the usual assay method (using human umbilical cord plasma and the association of 2 stimulating conditioned media: activated lymphocyte conditioned medium and bone marrow fibroblast conditioned medium), we found different circulating CFU-GM, Eo numbers. The mean number of circulating CFU-GM, Eo in 107 healthy adults was 22.4 per 2 x 10(5) plated cells (range: 1-84). There was a slight difference between males (mean number: 23.6) and females (mean number: 20.4). The mean number of CFU-GM, Eo harvested on Percoll gradient was 123/ml of peripheral blood (range: 7-513). These results are far over those commonly reported in literature. This suggests that these latter results were probably underestimated. The use of recombinant human interleukin 3 and recombinant human GM (granulocyte-monocyte) colony-stimulating factors shows that CFU-GM, Eo numbers are found to be comparatively increased compared to that obtained with our modified method (using rhIL-3 alone), or that the size of those colonies is notably increased (using rhIL-3 + rhGM-CSF).

Pathophysiology of aplastic anaemia

No single pathophysiological phenomenon--neither the intrinsic defect of haemopoiesis nor any of the described immune effects--explains aplastic anaemia. Since the intrinsic defect is compatible with near normal haemopoietic function, as seen in autologous bone marrow reconstitution, it cannot be the cause of severe pancytopenia. On the other hand, immune mechanisms cannot be the primary cause of the disease, otherwise haemopoietic function would recover to complete normality after immunosuppressive therapy. From these observations we deduce that the intrinsic defect, a premalignant haemopoietic disorder, can either be clinically quiescent by virtue of repair mechanisms, or induce auto-reactivity of the immune system against the abnormal haemopoietic tissue, drugs, chemicals and viruses acting as non-specific triggers or amplifiers. In this sense, aplastic anaemia could be interpreted as an attempt to 'self-cure' from a variant type of preleukaemia. This means that the original concept of aplastic anaemia being a hypoplastic variant of leukaemia may be true. The fact that aplastic anaemia can present either as acute severe bone marrow failure, as chronic mild pancytopenia or as a myelodysplasia-like syndrome does not imply that the underlying pathophysiological mechanisms are basically different. Variations of the clinical course and the response to immunosuppressive treatment could be explained by variations in the balance between the primary defect and the secondary immune reaction; the co-involvement of accessory cells in the primary disease; the relative time course of the two components and the efficiency of repair mechanisms. From repeated in vitro studies in a large group of aplastic anaemia patients at various stages of disease this concept can be applied to the majority of cases, including chloramphenicol- and virus-induced aplastic anaemia. In a small proportion of patients with pancytopenia occurring after exposure to certain drugs other than chloramphenicol, aplastic anaemia is rapidly and completely reversible after withdrawal of the drug. These patients probably have truly benign aplastic anaemia and thus differ from the majority of patients who are left with a permanently fragile bone marrow once they have acquired aplastic anaemia.

Do bone marrow fat cells or their precursors have a pathogenic role in idiopathic aplastic anaemia?

Idiopathic aplastic anaemia (AA), aplastic anaemia of unknown aetiology, is usually defined as marrow failure with fatty replacement of hemopoietic tissue and peripheral pancytopenia. The pathophysiology is largely unknown, though many mechanisms have been hypothesized. These include the absence of or defects in hemopoietic stem cells (HSC), abnormalities of the bone marrow (BM) microenvironment, immune system disorders and abnormalities of the regulatory factors that control hemopoiesis. The characteristic feature of AA is the replacement of hematopoietically active marrow by fat cells; however, the fat cells themselves have received little attention to date, and this apparent fatty marrow infiltration has been considered a secondary phenomenon. That the marrow fat cells in AA may be abnormal and may have a pathogenic role has never been considered. This communication, postulates that AA may result from an abnormal and excessive proliferation of marrow fat cells and the displacement of the hematopoietic tissue of the marrow; and that the resultant marrow failure could be a secondary phenomenon.

Drug-induced aplastic anaemia and agranulocytosis. Incidence and mechanisms

Aplastic anaemia and agranulocytosis are uncommon but serious adverse effects of drug therapy. They result from an adverse interaction between the drug and the haemopoietic pathway in certain susceptible individuals. The nature of this idiosyncratic interaction differs for different drugs and possibly for different individuals. In some instances an immune mechanism might be implicated, in others the patient's cells might carry a genetic susceptibility to the drug, while yet other patients might metabolise the drug abnormally. The idiosyncratic nature of these effects has made their investigation difficult, but experimental studies have allowed some progress in our understanding. In a practical sense, however, responsibility for preventing these problems will remain with clinicians, who should be alert to the risks and revise their prescribing habits accordingly.

Myeloid progenitor cells in the peripheral blood of patients with hairy cell leukemia and other "leukemic" lymphoproliferative disorders

We assayed granulocyte-macrophage committed progenitor cells (CFU-GM), erythroid committed progenitor cells (BFU-E) and pluripotent hemopoietic progenitor cells (CFU-MIX) in the peripheral blood of patients with hairy cell leukemia (HCL), acute lymphocytic leukemia (ALL) and chronic lymphocytic leukemia (CLL). In 8 HCL patients retaining their spleens, the number of circulating CFU-GM, BFU-E and CFU-MIX were under the lower limits of normal controls in 6, 6 and 5 cases, respectively, and were in the lower normal ranges in the remaining cases. Six splenectomized HCL patients had generally more circulating progenitor cells than their nonsplenectomized counterparts. In the peripheral blood of 2 patients with ALL and 3 patients with CLL, progenitor cells of all types were markedly increased compared to their respective values in the blood of control subjects. Hairy cells from 2 HCL patients failed to inhibit CFU-GM, BFU-E and CFU-MIX derived colony growth from control peripheral blood mononuclear cells. In 3 HCL patients previously low circulating progenitor cells did not rise 5-7 months after RC-alpha 2-IFN treatment despite normalization of peripheral blood counts. Our results suggest that a reduction of the committed and pluripotent progenitor cell compartment might be at least in part responsible for the pancytopenia in the majority of patients with HCL.

Drug-induced agranulocytosis: evidence for the commitment of bone marrow haematopoiesis

Clinical and haematological features of 61 patients with drug-induced agranulocytosis (63 episodes) are presented. Multiple drug consumption was a common observation and complicated the attempt to incriminate a particular drug as being aetiologically involved. Bone marrow analysis shortly after the diagnosis revealed evidence for an impairment of proliferative granulopoiesis in the majority of cases. This observation was confirmed by in vitro culturing of granuloid precursor cells (CFU-c). Moreover, the data clearly demonstrated that drug-induced agranulocytosis may not be restricted to the granulocytic series. Thrombocytosis and reticulocytosis during the recovery phase are taken as an indication for the commitment of all haemopoietic cell lineages in agranulocytosis. These observations were in accordance with cytomorphological studies and in vitro culture data of erythroid precursor cells (CFU-e, BFU-e) of bone marrow aspirates taken in the initial phase of agranulocytosis. More than 25% of the patients showed a marked erythroid depression in the marrow.

CFU-gm assay, cytochemical and electron microscopic studies in agar in patients with preleukemic syndrome and aplastic anemia

Thirty-seven patients with chronic cytopenia were studied using a CFU-gm assay in agar. Cell proliferation was evaluated on days 2, 3, 5, 7, and 10 of incubation. Growth patterns were different in cultures of hematologically healthy persons versus patients with preleukemic syndrome (PL) and aplastic anemia (AA). Three types of PL syndrome and two types of AA (C1 and C2) were distinguished. Bone marrow dysfunction was evaluated further using cytochemistry and electron microscopy to morphologically study cell proliferation in vitro. Cytochemical staining performed in agar demonstrated well-defined maturation defects in myelopoietic precursor cells from the bone marrow of PL patients. Electron microscopic findings of Auer-body-like inclusions in "statu nascendi" in the vacuoles of preleukemic cells supported our results. PL patient groups at high risk for development of overt leukemia and patients with grave prognosis in AA were distinguished. Our results are relevant for the clinical diagnosis and prognosis of patients with cytopenia.

Myelopoiesis and erythropoiesis of bone marrow cells cultured in vitro in patients recovered from aplastic anaemia

Methylcellulose culture assay was used to detect committed haemopoietic stem cells, CFU-C and CFU-E, in aplastic anaemia patients with autologous haemopoietic reconstitution. Severe diminution of CFU-C was found in all the patients studied and the absence of a dose-response to colony stimulating factor (CSF) was demonstrated. A reduced number of CFU-E and lower erythropoietin (Ep) sensitivity of those progenitors was detected as well. Autologous serum added to the bone marrow cultures of these patients enhanced the growth of CFU-C but inhibited CFU-E growth. According to the results presented, some residual damage at the stem cell level is suggested.

Serial incidence of bone marrow GM-CFC prior to the development of acute non-lymphoblastic leukaemia in a child treated for non-Hodgkin's lymphoma

A child treated for NHL developed acute non-lymphoblastic leukaemia 27 months after stopping treatment. Serial in vitro bone marrow studies showed a normal incidence of GM-CFC following treatment. However, GM-CFC incidence dropped at least 15 months prior to the development of leukaemia. This was associated with an asymptomatic neutropenia but no disturbance of bone marrow morphology. It is concluded that sub-clinical disturbances of bone marrow function may play an important part in leukaemogenesis.

Current considerations of the etiology of aplastic anemia

Aplastic anemia is a disorder characterized by marrow aplasia and pancytopenia. The pathogenetic mechanisms that lead to bone marrow aplasia have been intensively studied. Data obtained from these studies suggest that aplastic anemia is a heterogeneous disorder with regards to pathogenesis. Bone marrow aplasia may result from a number of abnormalities including qualitative or quantitative abnormalities of hematopoietic stem cells, abnormal interaction between bone marrow accessory cells (lymphocytes and macrophages) and hematopoietic stem cells, cytotoxic humoral inhibitors of hematopoiesis, and abnormalities of the bone marrow microenvironment. A number of new therapeutic options have improved the survival of patients with aplastic anemia. Allogeneic bone marrow transplantation has actually resulted in the cure of patients. Unfortunately, only a minority of patients have a suitable bone marrow donor and alternate modes of therapy have been sought. Encouraging results have been reported from several centers concerning the use of antilymphocyte serum in patients with aplastic anemia. Certainty of the ultimate long-term benefit of this type of immunosuppressive therapy is not possible until careful, randomized, prospective studies of its use are completed.

CFU-C inhibitors in aplastic anaemia

Peripheral blood lymphocytes from 15 patients with marrow aplasia were tested for their ability to inhibit the proliferation of normal granulopoietic precursor cells (CFU-C) in agar culture, relative to the inhibitory effect of normal lymphocytes studied in parallel. Eight of the 15 patients with marrow aplasia had lymphocytes which were significantly less inhibitory to normal CFU-C than controls whereas 3 patients had lymphocytes which were significantly more inhibitory. Two further patients who had recovered from marrow aplasia were also studied. The effect of patient's plasma and normal plasma on normal CFU-C proliferation was also studied and in 1 case a potent inhibitor of granulopoiesis was demonstrated. In 9 cases CFU-C could be cultured from patient's marrow, and parallel studies examining the effects of lymphocytes or plasma on patient's CFU-C were performed in these. All 9 patients had low numbers of marrow CFU-C. In none of the 9 marrow samples tested was inhibition by patient lymphocytes significantly greater than normal controls. The results highlight the heterogeneity inherent in the study of aplastic states and serve to underline the importance of controls. In only a minority of cases (20%) was lymphocyte suppression of normal granulopoiesis by lymphocytes from patients with aplastic anaemia significantly greater than normal lymphocyte suppression.

Aplastic anemia: recent advances in pathogenesis and treatment

Successful bone marrow transplantation and bone marrow culturing techniques have generated a large body of research into the pathogenesis and treatment of aplastic anemia. Most prominent has been the emphasis on autoimmune mechanisms. Several etiologic types and diagnostic criteria are discussed, the evidence supporting immune and other mechanisms of pathogenesis is examined, and results of current therapeutic trials are addressed.

Colony forming units in culture in childhood aplastic anemia

The results of the determination of the numbers of colony forming units in culture of the bone marrow of 17 children with aplastic anaemia before and after bone marrow transplantation, of 4 children with antilymphocyte globulin and of 16 children treated conventionally are presented. In the aplastic phase the number of C.F.U.-C. was very low to zero. After successful transplantation the number of bone marrow C.F.U.-C. rose but did not become normal. After antilymphocyte globulin and conventional therapy the number of bone marrow C.F.U.-C. remained low, even when a restoration of the haematological values in the peripheral blood took place.

Myeloid and erythroid colony growth in non-anaemic patients with Fanconi's anaemia

Myeloid and erythroid colony growth of the bone marrow and peripheral blood cells from one anaemic and four non-anaemic patients with Fanconi's anaemia were studied. Markedly decreased myeloid and erythroid colony growth was found in all five patients regardless of their haematological status. The decreased colony formation in non-anaemic patients with Fanconi's anaemia is thought to be due to an intrinsic cellular defect.

Reduced granulocyte-macrophage colony-stimulating activity by mitogen-stimulated lymphocytes from patients with aplastic anaemia

The ability of peripheral blood mononuclear cells from patients with idiopathic aplastic anaemia to provide colony-stimulating activity (CSA) was compared to that of normal controls. CSA was prepared by incubating peripheral blood mononuclear cells with phytohaemagglutinin. The supernatant derived from the latter is known as activated lymphocyte-conditioned medium (ALCM). The CSA of ALCM in eight patients was compared to that of normals in 12 experiments. In all but one instance there was decreased CSA by patient ALCM. Possible implications of these findings are discussed.

Prognostic factors in acquired aplastic anemia. A study of 352 cases

The prognostic factors of short- and long-term survival have been studied in 352 patients with aplastic anemia of all grades of severity. This group was homogeneous with regard to the clinical and laboratory survey, and the treatment used [high-dose androgen therapy]. The "hierarchy" of the individual prognostic parameters has been established: current severe infection, granulocyte count, percentage of the nonmyeloid cells on the bone marrow slides, platelet count, reticulocyte count, 59Fe utilization, and stromal disorganization on the bone marrow biopsy specimen. As these parameters are interrelated, a multiparametric analysis enables us to define groups of patients with different short-term evolution and to derive a prognostic index from these data. The use of such an index, however, allows a correct prediction in only 73 per cent of the cases, better in the milder than in the more severe cases. It is possible that the short-term evolutive tendency (improvement or worsening during the first six weeks of therapy) may contribute supplementary information useful for prognosis and the choice of treatment. After the first three months critical period, the mortality rate no longer depends on the initial severity of the disease but exclusively on the clinical and hematologic improvement. Thus, comparing the hematologic data obtained initially and after three months of androgen therapy allows us to correctly predict the long-term evolution.

Variations in granulocyte colony forming cell numbers in adult blood

Blood granulocyte colony forming units (CFU-C) were studied in normal adults to establish: (i) a normal range; (ii) variability due to the culture technique; (iii) variability of blood CFU-C within individuals. Thirty men studied had 98 (range 8--300) CFU-C X 10(3)/1, and 28 women studied had 44 (range 0--260) CFU-C X 10(3)/1. This difference was significant (P less than 0.001). There was also a significant sex difference in the total number of cells forming colonies and clusters per litre; and in the incidence of colony formers and of cluster formers in buffy coat and mononuclear cell blood fractions. CFU-C were assayed in four subjects over a 10 week period. When buffy coat cells were used as a source of colony stimulation the week to week variation in the combined growth of the four subjects was wide (+/- 36%) but with conditioned medium the variation was smaller (+/- 14%). In all subjects colony and cluster growth varied in the same way (r = 0.77, P = .001) but there was no correlation with the total leucocyte count. A 3--4 week cyclical change in CFU-C/1 was found which was independent of the variation inherent in the technique. The physiological significance of the sex difference and the apparent cyclical changes in blood CFU-C are not explained, but the results emphasize the wide fluctuations in CFU-C that may occur in normal individuals.

Effect of antilymphocyte globulin on granulocyte precursors in aplastic anaemia

Granylocyte colony forming units (CFU-C) were studied in 22 patients with severe aplastic anaemia before and after treatment with antilymphocyte globulin (ALG). Nine patients showed a clinical response to ALG characterized by a rise in the granulocyte count to over I X 10(9)/1 within 30 d. These patients were distinguished in vitro from non-responders by an increase in CFU-C numbers after incubation of bone marrow cells with ALG, and by the presence of inhibitors of normal CFU-C in the serum in six out of seven patients tested. In responding patients bone marrow CFU-C rose while most non-responding patients showed no change or a fall in CFU-C after treatment. In addition in three out of four responding patients examined serum inhibitors disappeared after treatment. The horse ALG used in this study also stimulated normal CFU-C in vitro. This evidence is contrary to the hypothesis that ALG stimulates CFU-C in aplasia by inactivating an abnormal suppressor lymphocyte population. The nature of the stimulation by ALG remains unclear. But in practice the effect of ALG on bone marrow cells and study of CFU-C inhibitors in serum could be used to select patients likely to respond to ALG treatment.

The proliferative states of circulating granulopoietic stem cells in man

The fraction of granulocyte-macrophage colony-forming cells (CFC) in DNA synthetic phase in blood from 25 normal adults and those in blood and bone marrow from 8 haematologically normal subjects were evaluated by in vitro culture of cells with and without prior exposure to 3H-thymidine (12.5 muCi) for 1 h at 37 degrees C. The exposure of blood cells from normal adults to 3H-thymidine resulted in 26 +/- 10% reduction in colony formation and in 14 +/- 10% reduction in cluster formation. There was no difference in the magnitude of reduction in colony formation following exposure to 3H-thymidine by cells in blood and those in bone marrow in 6 of the 8 haematologically normal subjects. These findings indicated that about one fourth of the circulating CFC in normal adults are in proliferative state and that significant difference in proliferative states between CFC in blood and those in bone marrow probably does not exist in the majority of haematologically normal subjects.

Studies on hematopoietic stem cells: XI. Lack of erythroid burst-forming units (BFU-E) in patients with aplastic anemia

The marrow concentration of erythropoietic precursors was examined in normal donors and patients with idiopathic aplastic anemia using a plasma clot culture system. On time course observations the heterogeneity of human erythroid precursors assayable in culture was demonstrated. To evaluate human erythropoiesis in vitro, the benzidine-positive colonies were divided into three groups: small colony, containing 8-50 cells; medium-sized colony, containing 50-500 cells; and large colony, containing more than 500 cells. The majority of the large colonies assumed the morphology of erythropietic bursts (BFU-E) consisted of several subcolonies. The small colonies were counted as CFU-E1, the medium-sized as CFU-E2, and the large as BFU-E to evaluate the erythroid precursor cell compartment in aplastic anemia. The marrow concentration of CFU-E1 and CFU-E2 was shown to be quantitatively diminished in aplastic anemia. In addition, there was no ability of the marrow cells from aplastic patieints to grow BFU-E in vitro even in the presence of a large dose of erythropoietin. This lack of BFU-E colony growth may play an important role in the mechanism of the erythropoietic deficiency in aplastic anemia.

Reaction of human granulopoiesis to high-dose cyclophosphamide therapy

The reaction pattern of an unperturbed human granulopoiesis to pulses of high-dose chemotherapy (cyclophosphamide 2000 mg/m2 plus vincristine 1.4 mg/m2 or adriamycin 20 mg/m2) was serially studied in 6 patients. The stem cells committed to granulopoiesis (CFU-C) of the bone marrow and the cells of the proliferative granulocytic marrow pool were considerably reduced during the first 8 days. Granulopoietic regeneration was first recognizable by increased proliferative activity of bone marrow CFU-C (3H-thymidine technique). The cytotoxic drug-induced injury to the early compartments of granulopoiesis, and granulocytic regeneration proceed sequentially through the ensuing, increasingly differentiated granulocytic compartments. In the peripheral blood, depletion and repletion of the CFU-C pool precede the corresponding changes of segmented neutrophils by 7 to 9 days; during granulocytic regeneration, peripheral blood CFU-C show a transient greatly overshooting decrease.

Changes of granulopoiesis during and after adjuvant chemotherapy of breast cancer

Adjuvant chemotherapy allows a study of the effects of cytotoxic drugs on natural human haematopoiesis. We describe serial studies of granulopoiesis performed during and after intermittent adjuvant chemotherapy for breast cancer (adriamycin plus cyclophosphamide, given for six courses at monthly intervals). After drug administration, a sequential wave of depletion and regeneration through successive granulopoietic compartments was observed. With repeated chemotherapy, moderate neutropenia developed, and the blood CFU-C pool size became progressively reduced. After the sixth chemotherapeutic course, granulopoietic regeneration was delayed. Following discontinuation of chemotherapy, a long-lasting (greater than 200 d) reduction of the blood CFU-C pool size, together with neutropenia and reduction of marrow segmented neutrophils, was observed, suggesting a defect of granulopoiesis with persistent granulopoietic hypoplasia. In patients with expected long survival, residual bone marrow damage should be added to the list of potential late side effects of cytotoxic drug therapy.

Severe aplastic anaemia with complete autologous marrow reconstitution following treatment with antithymocyte globulin. Report of a case and review of the literature

In a patient with end-stage acquired aplastic anaemia, unsuccessful treatment with splenectomy, prednisone, pyridoxine and anabolic steroid was followed by administration of antithymocyte globulin (ATG). This therapy soon led to a gradual improvement and after 12 months, complete remission was obtained. The possible mechanism of action of ATG and the general principles of treatment are discussed.

Erythroid colony forming cells in aplastic anaemia

The concentration and erythropoietin dependence of erythropoietic progenitor cells (CFU-E) were examined in 13 patients with aplastic anaemia at different stages of their disease. The CFU-E incidence was shown to be quantitatively diminished in aplastic anaemia but tended to recover to normal values if the disease recovered. In addition the CFU-E showed a qualitatively different response to stimulation by erythropoietin, being resistant to low concentrations but responsive to concentrations greater than 0.2 U/ml whereas there was a linear response in the controls up to 0.5 U/ml.