Cyclophosphamide-induced cyclical neutropenia. An animal model of a human periodic disease

The highs and lows of cyclic thrombocytopenia

Cyclic thrombocytopenia (CTP) is characterized by periodic platelet oscillation with substantial amplitude. Most CTP cases have a thrombocytopenic background and are often misdiagnosed as immune thrombocytopenia with erratically effective treatment choices. CTP also occurs during hydroxyurea treatment in patients with myeloproliferative diseases. While the aetiology of CTP remains uncertain, here we evaluate historical, theoretical and clinical findings to provide a framework for understanding CTP pathophysiology. CTP retains the intrinsic oscillatory factors defined by the homeostatic regulation of platelet count, presenting as reciprocal platelet/thrombopoietin oscillations and stable oscillation periodicity. Moreover, CTP patients possess pathogenic factors destabilizing the platelet homeostatic system thereby creating opportunities for external perturbations to initiate and sustain the exaggerated platelet oscillations. Beyond humoral and cell-mediated autoimmunity, we propose recently uncovered germline and somatic genetic variants, such as those of MPL, STAT3 or DNMT3A, as pathogenic factors in thrombocytopenia-related CTP. Likewise, the JAK2 V617F or BCR::ABL1 translocation that drives underlying myeloproliferative diseases may also play a pathogenic role in hydroxyurea-induced CTP, where hydroxyurea treatment can serve as both a trigger and a pathogenic factor of platelet oscillation. Elucidating the pathogenic landscape of CTP provides an opportunity for targeted therapeutic approaches in the future.

Understanding, treating and avoiding hematological disease: better medicine through mathematics?

This paper traces the experimental, clinical and mathematical modeling efforts to understand a periodic hematological disease-cyclical neutropenia. It is primarily a highly personal account by two scientists from quite different backgrounds of their interactions over almost 40 years and their attempts to understand this intriguing disease. It's also a story of their efforts to offer effective treatments for the patients who suffer from cyclic neutropenia and other conditions causing neutropenia and infections.

DNA interstrand crosslink repair and cancer

Interstrand crosslinks (ICLs) are highly toxic DNA lesions that prevent transcription and replication by inhibiting DNA strand separation. Agents that induce ICLs were one of the earliest, and are still the most widely used, forms of chemotherapeutic drug. Only recently, however, have we begun to understand how cells repair these lesions. Important insights have come from studies of individuals with Fanconi anaemia (FA), a rare genetic disorder that leads to ICL sensitivity. Understanding how the FA pathway links nucleases, helicases and other DNA-processing enzymes should lead to more targeted uses of ICL-inducing agents in cancer treatment and could provide novel insights into drug resistance.

Congenital neutropenia: diagnosis, molecular bases and patient management

The term congenital neutropenia encompasses a family of neutropenic disorders, both permanent and intermittent, severe (<0.5 G/l) or mild (between 0.5-1.5 G/l), which may also affect other organ systems such as the pancreas, central nervous system, heart, muscle and skin. Neutropenia can lead to life-threatening pyogenic infections, acute gingivostomatitis and chronic parodontal disease, and each successive infection may leave permanent sequelae. The risk of infection is roughly inversely proportional to the circulating polymorphonuclear neutrophil count and is particularly high at counts below 0.2 G/l.When neutropenia is detected, an attempt should be made to establish the etiology, distinguishing between acquired forms (the most frequent, including post viral neutropenia and auto immune neutropenia) and congenital forms that may either be isolated or part of a complex genetic disease.Except for ethnic neutropenia, which is a frequent but mild congenital form, probably with polygenic inheritance, all other forms of congenital neutropenia are extremely rare and have monogenic inheritance, which may be X-linked or autosomal, recessive or dominant.About half the forms of congenital neutropenia with no extra-hematopoietic manifestations and normal adaptive immunity are due to neutrophil elastase (ELANE) mutations. Some patients have severe permanent neutropenia and frequent infections early in life, while others have mild intermittent neutropenia.Congenital neutropenia may also be associated with a wide range of organ dysfunctions, as for example in Shwachman-Diamond syndrome (associated with pancreatic insufficiency) and glycogen storage disease type Ib (associated with a glycogen storage syndrome). So far, the molecular bases of 12 neutropenic disorders have been identified.Treatment of severe chronic neutropenia should focus on prevention of infections. It includes antimicrobial prophylaxis, generally with trimethoprim-sulfamethoxazole, and also granulocyte-colony-stimulating factor (G-CSF). G-CSF has considerably improved these patients' outlook. It is usually well tolerated, but potential adverse effects include thrombocytopenia, glomerulonephritis, vasculitis and osteoporosis. Long-term treatment with G-CSF, especially at high doses, augments the spontaneous risk of leukemia in patients with congenital neutropenia.

Haemotoxicity of busulphan, doxorubicin, cisplatin and cyclophosphamide in the female BALB/c mouse using a brief regimen of drug administration

Many anticancer drugs are myelotoxic and cause bone marrow depression; however, generally, the marrow/blood returns to normal after treatment. Nevertheless, after the administration of some anti-neoplastic agents (e.g. busulphan, BU) under conditions as yet undefined, the marrow may begin a return towards normal, but normality may not be achieved, and late-stage/residual marrow injury may be evident. The present studies were conducted to develop a short-term mouse model (a 'screen') to identify late-stage/residual marrow injury using a brief regimen of drug administration. Female BALB/c mice were treated with BU, doxorubicin (DOX), cisplatin (CISPLAT) or cyclophosphamide (CYCLOPHOS) on days 1, 3 and 5. In 'preliminary studies', a maximum tolerated dose (MTD) for each drug was determined for use in 'main studies'. In main studies, mice were treated with vehicle (control), low and high (the MTD) dose levels of each agent. Necropsies were performed, and blood parameters and femoral/humeral nucleated marrow cell counts (FNCC/HNCC) were assessed on six occasions (from days 1 to 60/61 post-dosing). Late-stage/residual changes were apparent in BU-treated mice at day 61 post-dosing: RBC, Hb and haematocrit were reduced, mean cell volume/mean cell haemoglobin were increased and platelet and FNCC counts were decreased. Mice given DOX, CISPLAT and CYCLOPHOS, in general, showed no clear late-stage/residual effects (day 60/61). It was concluded that a brief regimen of drug administration, at an MTD, with assessment at day 60/61 post-dosing was a suitable short-term method/screen in the mouse for detecting late-stage/residual marrow injury for BU, a drug shown to exhibit these effects in man.

[Granulopoeisis and leukemogenesis: lessons from congenital neutropenia]

Congenital neutropenia are extremely rare diseases, defined by a permanent or cyclic decrease of blood neutrophils. Molecular basis of several congenital neutropenia has been recently determined, involving gene coding for the neutrophil elastase gene (ELA2), GFI1, WAS protein and mitochondrial HAX1 protein. These mutations, dominant (ELA2, GFI1), X-linked (WAS) and autosomal recessive (HAX1), result in instability of the contents of the granules- particularly the neutrophil elastase- or in abnormalities of the cytoskeleton, and possibly, in an increased apoptosis. ELA2 mutations resulting both in profound and permanent neutropenia, and in cyclic--pseudo sinusoidal--neutropenia lead to consider that time pattern is very close in the two apparently distinct phenotypes. This observation suggests that temporal variations of neutrophils could be represented by non linear functions. Congenital neutropenia, specifically ELA2 mutated, are also characterized by a high rate of leukemia (about 15% at 20 years of age). Leukemia risk does not appear to be related to an oncogenic effect of ELA2 mutations, but much likely to the deepness of the neutropenia, and the intensity of G-CSF therapy.

Neutropenia induced in outbred mice by a simplified low-dose cyclophosphamide regimen: characterization and applicability to diverse experimental models of infectious diseases

Background

For its low cost and ease of handling, the mouse remains the preferred experimental animal for preclinical tests. To avoid the interaction of the animal immune system, in vivo antibiotic pharmacodynamic studies often employ cyclophosphamide (CPM) to induce neutropenia. Although high doses (350–450 mg/kg) are still used and their effects on mouse leukocytes have been described, a lower dose (250 mg/kg) is widely preferred today, but the characteristics and applicability of this approach in outbred mice have not been determined.

Methods

Fifteen female ICR mice were injected intraperitoneally with 150 and 100 mg/kg of CPM on days 1 and 4, respectively. Blood samples (~160 μL) were drawn from the retro-orbital sinus of each mouse on days 1, 4, 5, 6, 7 and 11. Leukocytes were counted manually and the number of granulocytes was based on microscopic examination of Wright-stained smears. The impact of neutropenia induced by this method was then determined with a variety of pathogens in three different murine models of human infections: pneumonia (Klebsiella pneumoniae, Streptococcus pneumoniae, Staphylococcus aureus), meningoencephalitis (S. pneumoniae), and the thigh model (S. aureus, Escherichia coli, Bacteroides fragilis).

Results

The basal count of leukocytes was within the normal range for outbred mice. On day 4, there was an 84% reduction in total white blood cells, and by day 5 the leukopenia reached its nadir (370 ± 84 cells/mm³). Profound neutropenia (≤10 neutrophils/mm³) was demonstrated at day 4 and persisted through days 5 and 6. Lymphocytes and monocytes had a 92% and 96% decline between days 1 and 5, respectively. Leukocytes recovered completely by day 11. Mice immunosupressed under this protocol displayed clinical and microbiological patterns of progressive and lethal infectious diseases after inoculation in different organs with diverse human pathogens.

Conclusion

A CPM total dose of 250 mg/kg is sufficient to induce profound and sustained neutropenia (<10 neutrophils/mm³) at least during 3 days in outbred mice, is simpler than previously described methods, and allows successful induction of infection in a variety of experimental models.

Cyclical mobilization and gated importation of thymocyte progenitors in the adult mouse: evidence for a thymus-bone marrow feedback loop

It has recently been observed, as in the fetal thymus, that the importation of hematogenous thymocyte progenitors by the adult thymus is a gated phenomenon, whereby saturating numbers of progenitors periodically enter the thymus and occupy a finite number of intrathymic niches. In addition, the mobilization of thymocyte progenitors from the bone marrow appears to be a cyclical process that coincides temporally with the periods of thymic receptivity (open gate). It is proposed that these events are coordinated by a thymus-bone marrow feedback loop in which a wave of developing triple negative (CD3- CD4- CD8-) thymocytes interacts with stromal cells in the stratified regions of the thymus cortex to sequentially induce the release of diffusible cytokines that regulate the production, mobilization, and recruitment of thymocyte progenitors. The likely components of this feedback loop are described here, as are the properties of the intrathymic vascular gates and niches for thymocyte progenitors. The cyclical production and release of thymocyte progenitors from the bone marrow is placed in the context of a general phenomenon of oscillatory feedback regulation involving all lymphohemopoietic cell lineages. Lastly, the question of whether the gated (as opposed to the continuous) entry of thymocyte progenitors is essential for normal thymocytopoiesis in adult life is discussed.

A mathematical model of hematopoiesis: II. Cyclical neutropenia

Cyclical neutropenia is a dynamical disease of the hematopoietic system marked by an oscillation in circulating leukocyte (e.g. neutrophil) numbers to near zero levels and then back to normal. This oscillation is also mirrored in the platelets and reticulocytes which oscillate with the same period. Cyclical neutropenia has an animal counterpart in the grey collie. Using the mathematical model of the hematopoietic system of Colijn and Mackey [A mathematical model of hematopoiesis: I. Periodic chronic myelogenous leukemia. Companion paper to the present paper.] we have determined what parameters are necessary to mimic laboratory and clinical data on untreated grey collies and humans, and also what changes in these parameters are necessary to fit data during treatment with granulocyte colony stimulating factor (G-CSF). Compared to the normal steady-state values, we found that the major parameter changes that mimic untreated cyclical neutropenia correspond to a decreased amplification (increased apoptosis) within the proliferating neutrophil precursor compartment, and a decrease in the maximal rate of re-entry into the proliferative phase of the stem cell compartment. For the data obtained during G-CSF treatment, good fits were obtained only when parameters were altered that would imply that G-CSF led to higher amplification (lower rate of apoptosis) in the proliferating neutrophil precursors, and a elevated rate of differentiation into the neutrophil line.

Oscillations in cyclical neutropenia: new evidence based on mathematical modeling

We present a dynamical model of the production and regulation of circulating blood neutrophil number. This model is derived from physiologically relevant features of the hematopoietic system, and is analysed using both analytic and numerical methods. Supercritical Hopf bifurcations and saddle-node bifurcations of limit cycles are shown to exist. We make the estimation of kinetic parameters for dogs and then apply the model to cyclical neutropenia (CN) in the grey collie, a rare disorder in which oscillations in all blood cell counts are found. We conclude that the major cause of the oscillations in CN is an increased rate of apoptosis of neutrophil precursors which leads to a destabilization of the hematopoietic stem cell compartment.

Chronic myelogenous leukemia as a paradigm of early cancer and possible curative strategies

The chronological history of the important discoveries leading to our present understanding of the essential clinical, biological, biochemical, and molecular features of chronic myelogenous leukemia (CML) are first reviewed, focusing in particular on abnormalities that are responsible for the massive myeloid expansion. CML is an excellent target for the development of selective treatment because of its highly consistent genetic abnormality and qualitatively different fusion gene product, p210(bcr-abl). It is likely that the multiple signaling pathways dysregulated by p210(bcr-abl) are sufficient to explain all the initial manifestations of the chronic phase of the disease, although understanding of the circuitry is still very incomplete. Evidence is presented that the signaling pathways that are constitutively activated in CML stem cells and primitive progenitors cooperate with cytokines to increase the proportion of stem cells that are activated and thereby increase recruitment into the committed progenitor cell pool, and that this increased activation is probably the primary cause of the massive myeloid expansion in CML. The cooperative interactions between Bcr-Abl and cytokine-activated pathways interfere with the synergistic interactions between multiple cytokines that are normally required for the activation of stem cells, while at the same time causing numerous subtle biochemical and functional abnormalities in the later progenitors and precursor cells. The committed CML progenitors have discordant maturation and reduced proliferative capacity compared to normal committed progenitors, and like them, are destined to die after a limited number of divisions. Thus, the primary goal of any curative strategy must be to eliminate all Philadelphia positive (Ph+) primitive cells that are capable of symmetric division and thereby able to expand the Ph+ stem cell pool and recreate the disease. Several highly potent and moderately selective inhibitors of Bcr-Abl kinase have recently been discovered that are capable of killing the majority of actively proliferating early CML progenitors with minimal effects on normal progenitors. However, like their normal counterparts, most of the CML primitive stem cells are quiescent at any given time and are relatively invulnerable to the Bcr-Abl kinase inhibitors as well as other drugs. We propose that survival of dormant Ph+ stem cells may be the most important reason for the inability to cure the disease during initial treatment, while resistance to the inhibitors and other drugs becomes increasingly important later. An outline of a possible curative strategy is presented that attempts to take advantage of the subtle differences in the proliferative behavior of normal and Ph+ stem cells and the newly discovered selective inhibitors of Bcr-Abl. Leukemia (2003) 17, 1211-1262. doi:10.1038/sj.leu.2402912

Modeling complex neutrophil dynamics in the grey collie

We have developed a mathematical model for the peripheral regulation of neutrophil production mediated by granulocyte colony-stimulating factor. We have used that model to show that the pattern of neutrophil oscillations in nine grey collies is consistent with the hypothesis that cyclical neutropenia is due to an oscillatory stem cell input to the neutrophil regulatory system, and not due to autonomous oscillations in the peripheral neutrophil regulatory system. In the process of interfacing our model with the laboratory data, we have estimated parameters for the peripheral neutrophil control system consistent with higher than normal apoptotic cell loss within the recognizable neutrophil precursors. This is in agreement with other experimental data. Our estimated model parameters also predict that the peripheral neutrophil production system is globally stable in the grey collies we studied. This further supports our hypothesis that the origin of the oscillatory behavior in cyclical neutropenia is in the stem cell population, consistent with other clinical and experimental evidence.

Hematopoietic dynamics in grey collies

Using Lomb periodogram analysis we have quantified variations in the peripheral neutrophil and platelet counts of the cyclical neutropenia animal model-the grey collie. We found that the amplitudes of the oscillations in these two cell lineages vary concomitantly. Further, the power spectrum and the shape of the oscillations in the absolute neutrophil counts vary together with the amplitude of the oscillations. As the amplitude of the oscillations increases, the height of the second subharmonic increases, giving rise to a distorted oscillation with two peaks per cycle. The particular dynamics of the absolute neutrophil counts can be reproduced by a combination of a delayed peripheral feedback, representing the peripheral control of granulopoiesis through granulocyte colony stimulating factor, together with a sinusoidal input representing an oscillatory input from the pluripotential stem cells to the granulocytic lineage. The same pluripotential stem cell input is probably responsible for the sinusoidal oscillations observed in the other cell lineages.

Cyclical Neutropenia and Other Periodic Hematological Disorders: A Review of Mechanisms and Mathematical Models

Although all blood cells are derived from hematopoietic stem cells, the regulation of this production system is only partially understood. Negative feedback control mediated by erythropoietin and thrombopoietin regulates erythrocyte and platelet production, respectively, but the regulation of leukocyte levels is less well understood. The local regulatory mechanisms within the hematopoietic stem cells are also not well characterized at this point. Because of their dynamic character, cyclical neutropenia and other periodic hematological disorders offer a rare opportunity to more fully understand the nature of these regulatory processes. We review the salient clinical and laboratory features of cyclical neutropenia (and the less common disorders periodic chronic myelogenous leukemia, periodic auto-immune hemolytic anemia, polycythemia vera, aplastic anemia, and cyclical thrombocytopenia) and the insight into these diseases afforded by mathematical modeling. We argue that the available evidence indicates that the locus of the defect in most of these dynamic diseases is at the stem cell level (auto-immune hemolytic anemia and cyclical thrombocytopenia seem to be the exceptions). Abnormal responses to growth factors or accelerated cell loss through apoptosis may play an important role in the genesis of these disorders.

© 1998 by The American Society of Hematology.

Cyclical Neutropenia and Other Periodic Hematological Disorders: A Review of Mechanisms and Mathematical Models

Although all blood cells are derived from hematopoietic stem cells, the regulation of this production system is only partially understood. Negative feedback control mediated by erythropoietin and thrombopoietin regulates erythrocyte and platelet production, respectively, but the regulation of leukocyte levels is less well understood. The local regulatory mechanisms within the hematopoietic stem cells are also not well characterized at this point. Because of their dynamic character, cyclical neutropenia and other periodic hematological disorders offer a rare opportunity to more fully understand the nature of these regulatory processes. We review the salient clinical and laboratory features of cyclical neutropenia (and the less common disorders periodic chronic myelogenous leukemia, periodic auto-immune hemolytic anemia, polycythemia vera, aplastic anemia, and cyclical thrombocytopenia) and the insight into these diseases afforded by mathematical modeling. We argue that the available evidence indicates that the locus of the defect in most of these dynamic diseases is at the stem cell level (auto-immune hemolytic anemia and cyclical thrombocytopenia seem to be the exceptions). Abnormal responses to growth factors or accelerated cell loss through apoptosis may play an important role in the genesis of these disorders.

© 1998 by The American Society of Hematology.

Clinical interpretation of leukocyte responses

Basic information has been presented concerning leukocyte (neutrophil, monocyte, lymphocyte, eosinophil, and basophil) function, production, kinetics, and response to various physiological and disease states. Using this information, veterinary practitioners should be able to interpret leukogram data from sick and healthy dogs and cats. Specifically, characteristic leukogram patterns such as physiological leukocytosis, corticosteroid-associated changes, and the presence of infection or severe inflammation should be recognized. In addition, interpretation of individual leukocyte responses should be possible. Several tables have been provided to assist in constructing a differential diagnosis to explain increases or decreases in absolute leukocyte numbers that lie outside of expected reference intervals.

A discrete mathematical model of unlabelled granulocyte kinetics. A preliminary study of feedback control

The equations used in formulating the continuous model of granulocyte kinetics developed by O'Fallon et al. (1971) were analyzed to see if they could be altered to simulate a feedback mechanism operating on the production and development of granulocytes. After extensive study and modification of the continuous model, it was found that a discrete model based on a Leslie matrix procedure was more effective for simulating the feedback system. This discrete model was used to show experimentally, from a mathematical view point, that a feedback mechanism of some kind must be operating on the production and development of granulocytes. Further, the discrete model was subjected to preliminary tests (simultaneous and cascading feedback) to demonstrate that it has the capability of responding to feedback control.

Chronobiology in hematology and immunology

The hematopoietic and the immune systems in all their components are characterized by a multifrequency time structure with prominent rhythms in cell proliferation and cell function in the circadian, infradian, and rhythms in cell proliferation and cell function in the circadian, infradian, and circannual frequency ranges. The circulating formed elements in the peripheral blood show highly reproducible circadian rhythms. The timing and the extent of these rhythms were established in a clinically healthy human population and are shown as chronograms, cosinor summaries and, for some high-amplitude rhythms, as time-qualified reference ranges (chronodesms). Not only the number but also the reactivity of circulating blood cells varies predictably as a function of time as shown for the circadian rhythm in responsiveness of human and murine lymphocytes in vitro to lectin mitogens (phytohemagglutinin and pokeweed mitogen). Some circadian rhythms of hematologic functions appear to be innate and are presumably genetically determined but are modulated and adjusted in their timing by environmental factors, so-called synchronizers. Phase alterations in the circadian rhythms of hematologic parameters of human subjects and of mice by manipulation of the activity-rest or light-dark schedule and/or of the time of food uptake are presented. Characteristically these functions do not change their timing immediately after a shift in synchronizer phase but adapt over several and in some instances over many transient cycles. The circadian rhythm of cell proliferation in the mammalian bone marrow and lymphoid system as shown in mice in vivo and in vitro may lend itself to timed treatment with cell-cycle-specific and nonspecific agents in an attempt to maximize the desired and to minimize the undesired treatment effects upon the marrow. Differences in response, and susceptibility of cells and tissues at different stages of their circadian and circaseptan (about 7-day) rhythms and presumably of cyclic variations in other frequencies are expected to lead to the development of a chronopharmacology of the hematopoietic and immune system. Infradian rhythms of several frequencies have been described for numerous hematologic and immune functions. Some of these, i.e., in the circaseptan frequency range, seem to be of importance for humoral and for cell mediated immune functions including allograft rejection. Infradian rhythms with periods of 19 to 22 days seem to occur in some hematologic functions and are very prominent in cyclic neutropenia and (with shorter periods) in its animal model, the grey collie syndrome.(ABSTRACT TRUNCATED AT 400 WORDS)

Periodic neutropenia and monocytopenia

A patient with periodic neutropenia exhibited simultaneous monocytopenia, and epinephrine infusion revealed no monocytes in the marginating pool during neutropenia. Lymphocytes, eosinophils, and platelets also fluctuated periodically, but serial bone marrow studies and epinephrine infusion data indicate these fluctuations could have represented epiphenomena rather than a more global form of periodic hematopoiesis. Bone marrow descriptions of most cases of periodic neutropenia have indicated a "maturation arrest" at the promyelocyte or myelocyte stage prior to development of neutropenia; peripheral blood monocytes are usually normal or fluctuate out of phase with neutrophils. In this present case, "maturation arrest" occurred at the myeloblast stage, and neutrophils and monocytes cycled together. Morphologically normal eosinophilopoiesis with a mean eosinophil to erythroid ratio in the marrow of 0.27 +/- 0.10 (SD) persisted despite a sustained disappearance of promyelocytes.

Circaseptan (about-7-day) bioperiodicity--spontaneous and reactive--and the search for pacemakers

A built-in (genetically determined) about-7-day (circaseptan) period comes to the fore as a desynchronized feature of human time structure in the urinary excretion of 17-ketosteroids by a clinical healthy man: during several years following an endocrine intervention (the self-administration of testosterone suppositories), a circaseptan rhythm (which during the preceding decade had revealed a period of precisely 7 days) deviated slightly, yet with statistical significance, from the environmental week. A second line of evidence for an intrinsic circaseptan component stems from the demonstration of statistically significant differences in timing of a circaseptan rhythm in springtail oviposition. A third line of evidence documents prominent circaseptan rhythmicity after the application of a single stimulus (devoid in itself of any circaseptan information). Such single stimulus induction, amplification and/or synchronization also documents the clinical and biologic importance of built-in circaseptan rhythms that were previously often misinterpreted as being purely reactive: a circaseptan spectral component is remarkably prominent in mammalian organ transplant rejection, both in the clinic and in the laboratory. In the latter case, in the absence of any weekly cycles in hospital routine, including treatment schedules, circaseptan components characterize the rejection of the rat kidney, pancreas and heart. Much additional information here reviewed reveals the occurrence of periods of about 7 days. Their implications for transplant and other chronoimmunology as well as biology in general, and their clinical applications in drug treatment, include the need to weld circaseptan timing to circadian timing and dosing. A dramatic documentation of this need stems from the circumstance that pretreatment for one week with the same total dose of the same substance (a polysaccharide - Lentinan) accelerates or retards cancerous growth (hence shortens or lengthens survival) as a function of interactive circaseptan and circadian rhythms.

Cyclic neutropenia and T lymphocyte suppression of granulopoiesis: abrogation of the neutropenic cycles by lithium carbonate

To investigate the mechanisms of cyclic neutropenia, we studied the capacity of a patient's T lymphocytes (TLp) to interact with monocyte-macrophages from her normal HLA-identical sibling (MOb) in the elaboration of colony-stimulating activity (CSA). TLp obtained at the time of decreasing neutrophil counts, increased CSA elaboration (p less than 0.056) when incubated at a 1:1 ratio with MOb. Increasing the TLp to MOb ratios to 3:1 or 5:1 progressively decreased CSA. Also, lithium carbonate, which ordinarily prevents concanavalin A activation of suppressor TL, failed to do so, suggesting that preactivated suppressor TL were present in the patient while neutrophil levels were falling. In similar experiments performed while neutrophil levels were rising these activated suppressor TL were absent. These data suggest that some patients with cyclic neutropenia may have a cyclic increase in suppressor TL activity. As predicted by our in vitro experiments, lithium carbonate administration did not abrogate the first neutropenic cycle, but it did mitigate subsequent cycles.

The effect of lithium on murine hematopoiesis in a liquid culture system

Lithium carbonate has been shown to increase granulocyte production. We studied the effect of lithium on murine hematopoiesis in a liquid culture system providing for the prolonged growth of stem cells and their progeny. After one week of incubation, lithium, at a supernatant concentration of 1 mmol per liter, increased murine pluripotent stem cells (CFU-S, or colony-forming units in spleen) to 232 per cent of control values (P less than 0.001), granulocyte-monocyte progenitor cells (CFU-C, or colony-forming units in culture) to 218 per cent of control values (P less than 0.0001), granulocytes to 125 per cent of control values (P less than 0.01), and megakaryocytes to 246 per cent of control values (P less than 0.001). These increases were associated with transient elevations in colony-stimulatory activity. Prolonged exposure to lithium (three to 12 weeks) was associated with a dose-dependent progressive depletion of stem cells and their progeny. Lithium enhancement of granulopoiesis may be explained by primary stimulation of the pluripotent stem cell. Prolonged proliferative stress induced by lithium when the stem-cell reserve is limited may be associated with diminished replicative potential of the stem cells and rapid depletion of cells.

Some immunological and haematological aspects of human cyclic neutropenia

In addition to standard peripheral blood cell counts, sequential studies have been made of changes in the T-lymphocyte population and in the serum titres of the presumptive humoral regulators of haematopoiesis, Colony Stimulating Activity (CSA) and Erythroid Stimulating Activity (ESA), in a young woman with cyclic neutropenia (CN). In addition, serum immunoglobulins, C3 and total complement levels and serum protein concentrations were determined on several occasions during the study. Similar tests were done concomitantly on a haematologically normal, age and sex-matched control. Cell counts on peripheral blood from the subject with CN demonstrated a clearly defined periodicity in neutrophil and monocyte concentrations and equivocal fluctuations in reticulocyte numbers. There was no evidence of periodicity in the lymphocyte concentrations and the T-lymphocyte population appeared functionally normal. Spontaneous incorporation of tritiated thymidine into peripheral blood cells showed a highly significant correlation with the monocyte count, suggesting that these cells were responsible for the radioisotope uptake. CSA titres were elevated on all occasions tested and showed no evidence of periodicity. ESA showed some evidence of cycling with elevated levels being observed during the periods of neutropenia. Serum complement levels were within the normal range but all classes of immunoglobulins were elevated and albumin levels were depressed.

Correction of human cyclic neutropenia with prednisolone

A 70-year-old woman with cyclic neutropenia was treated with 16 mg of etiocholanolone and 25 mg of prednisolone intramuscularly every other day. During 14 weeks' treatment amplitude of cyclic fluctuations in neutrophil counts gradually decreased, but pretreatment cycles returned promptly after treatment was stopped. Prednisolone alone every other day (25 mg) reproduced this result, and by 23 weeks, neutrophil counts became stable at about 1500 per cubic millimeter. tcycling of monocytes, platelets and reticulocytes was also eliminated, as were symptoms that had accompanied neutropenic periods. In addition, bone-marrow neutrophil precursors and neutrophil marrow reserves were stabilized. The patient was subsequently maintained satisfactorily with oral prednisolone, 20 mg every other day. These studies demonstrate that the discontinuous myeloid maturation that occurs in cyclic neutropenia can be corrected with prednisolone every other day.

Cell kinetics in human cyclic neutropenia

Cell kinetics have been studied at several periods in a patient with typical cyclic neutropenia. Peripheral blood granulocyte labelling showed an increased destruction in the preleucopenic phase. Bone marrow colony-forming cells and blood leucocyte colony forming activity were normal or above the normal range. The major abnormalities were found in sequential studies of bone marrow proliferation measured by "in vitro" 3H-thymidine flash labelling. A fall in the labelling index of promyelocytes was observed in the second part of the cycle. Incubation of normal human bone marrow cells with patient's granulocytes showed a marked decrease in 3H-thymidine incorporation, compared with incubation with the same number of normal granulocytes. Human cyclic neutropenia seems to be due to a factor secreted by abnormal polymorphonuclears inhibiting myeloid proliferation.

[Kinetics and regulation of granulocytopoiesis (author's transl)]

The present survey of the development of the granulocytes consists of two parts. In the first section the different stages of granulopoiesis are discussed with special regard to the stem cells. In the second one the regulation of the granulopoiesis and the different factors taking part in the homeostasis of the granulocytes are examined. Emphasis is placed upon the colony stimulating activity" (CSA) previously tested in different situations of stress in relationship to the granulopoietic system. In a separate chapter some marked clinical syndromes are discussed which accompany disorders of granulocyte-homeostasis. The pathogenesis of leukaemia is reviewed.

Alteration of colony-stimulating factor output, endotoxemia, and granulopoiesis in cyclic neutropenia

Cellular and humoral factors involved in the regulation of granulopoiesis were evaluated in two patients with cyclic neutropenia by utilizing the agar-gel marrow culture technique to serially study marrow granulocytic colony-forming capacity (CFC) and the urinary output of colony-stimulating factor (CSF). CSF output varied inversely with peripheral neutrophil counts and directly with monocyte counts and evidence for infection (endotoxemia and/or staphylococcal abscesses). Following autologous infusion of one patient's plasma obtained during a period of neutropenia, increased urinary excretion of CSF occurred concomitant with increments in both marrow CFC and the proportion of granulocytic progenitor cells in DNA synthesis. Neutrophil periodicity was not altered by the administration of the neutropenic plasma. These findings are consistent with the hypothesis that cyclic neutropenia is caused by a quantitatively decreased entry of stem cells or granulocytic progenitor cells into granulopoiesis.

Hematopoiesis in the grey collie dog: studies of the regulation of erythropoiesis

Hematopoiesis in the grey collie dog undergoes periodic fluctuations which involve reticulocytes, granulocytes, platelets, lymphocytes, and monocytes. This syndrome is inherited in an autosomal recessive manner and can be transmitted or abolished by appropriate bone marrow transplantation experiments, thus demonstrating this to be a primary marrow defect. Investigation of humoral regulation in this setting indicates that serum erythropoietin (ESF) also undergoes cyclic fluctuation and that shortly after the increase and peak in serum ESF levels recognizable red cell precursors appear in the marrow. Erythropoiesis in the grey collie is reciprocally related to the blood O2 carrying capacity. With phlebotomy, ESF activity and reticulocytes increase but continue to cycle, while hypertransfusion eliminates reticulocyte production completely. Neither phlebotomy nor hypertransfusion alter the underlying cycle time (11-12 days) nor influence the peaks of peripheral blood granulocytes. Thus, in these experiments, no direct evidence of competition between reticulocyte and granulocyte production is observed. In vitro studies of canine hemoglobin synthesis fail to demonstrate evidence of an inhibitor to ESF. These results indicate that periodic fluctuation of serum ESF is an integral part of the grey collie syndrome and are most consistent with some form of feedback regulation of ESF production.

Anabolic steroids and bone marrow toxicity during therapy with methotrexate

The effect of the anabolic steroids nandrolone decanoate and oxymetholone on the peripheral blood haemoglobin, total leucocyte and platelet counts was studied in a controlled trial in which patients received standardized chemotherapy for one form of malignant disease. The results indicate that these agents have no protective effect on bone marrow suppression during cytotoxic chemotherapy. It was observed that the time interval between the initial nadir total leucocyte count and the return to pre-treatment values in those patients receiving the anabolic steroids was significantly shorter than in the control group.

Cyclic hematopoiesis: the mechanism of cyclic neutropenia in grey collie dogs

Two grey collie dogs had regular cyclic fluctuations in the number of all formed elements of the blood. The period lengths for all elements for an individual dog were the same, but the pattern of fluctuation for each element was distinctive. Normal dogs lacked periodic fluctuations.The patterns of day-to-day variation in the normal dogs counts were consistent with a first-order autoregressive process of serial dependence (i.e., each observation of the series depends on the last preceding observation and no others). The grey collie counts showed the same pattern of serial dependence after the component of the over-all variability due to cyclic oscillation was removed. These data suggest that a defect of hematopoietic regulation at the stem cell level leads to periodic interruptions of production of all hematopoietic elements and accounts for the cycles seen in the peripheral blood counts.