LEUKOKINETIC STUDIES. XI. BLOOD GRANULOCYTE KINETICS IN POLYCYTHEMIA VERA, INFECTION, AND MYELOFIBROSIS

A mathematical model of neutrophil production and control in normal man

A comprehensive mathematical model of neutrophil production in normal man is presented. The model incorporates three control elements which regulate homeostatically the rates of release of marrow cells to proliferation, maturation, and to the blood. The steady state properties of the model are demonstrated analytically. The basic equations of the model, which are nonlinear, have been integrated numerically. The solutions so obtained display graphically the dynamical response of the system to various perturbations, which simulate experimental investigations that have been made in the past of granulocytopoiesis. By an appropriate choice of values of the parameters characterizing the system, it is shown how most of the principal kinetic properties of the neutrophil production and control system are represented in a quantitative manner.

Mathematical modeling supports the presence of neutrophil depriming in vivo

Following migration into the intestinal mucosa in inflammatory bowel disease (IBD), neutrophils enter the intestinal lumen and are excreted. This provides a basis for quantification of disease activity by measuring excreted label following injection of In‐111‐labeled neutrophils. In severe pan‐colitis, 50% of the injected In‐111 is typically recovered in the feces, indicating that 50% of neutrophil turnover is via fecal excretion. Neutrophils have an intravascular lifespan of ~10 h and a distribution volume of ~10 L, so total body neutrophil turnover is 10.N/10 cells/h, where N is the peripheral blood neutrophil count (cells/L). Neutrophil loss via the colon in a patient with 50% fecal In‐111 loss is therefore N/120 cells/min. Pan‐colonic mucosal‐blood flow in pan‐colitis is 200 mL/min, which would deliver N/5 neutrophils to the colon per min. Therefore, 5/120, or 4%, of incoming neutrophils undergo migration into inflamed bowel. If the 96% of nonmigrating cells exit in a primed state, then at steady state >90% of circulating neutrophils would be primed if no depriming took place. As the highest level of priming seen in IBD is ~40%, this indicates that depriming within the circulation must take place. Using the above values in the steady state equation relating priming rate to depriming rate plus primed‐cell destruction rate gives a mean depriming time of 35 min. We conclude that a very small proportion of neutrophils entering a site of inflammation migrate and that in vivo depriming must take place to limit the numbers of primed neutrophils in the circulation.

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Following migration into the intestinal mucosa in inflammatory bowel disease (IBD), neutrophils enter the intestinal lumen and are excreted. This provides a basis for quantification of disease activity by measuring excreted label following injection of In‐111‐labeled neutrophils. In severe pan‐colitis, 50% of the injected In‐111 is typically recovered in the feces, indicating that 50% of neutrophil turnover is via fecal excretion. Neutrophils have an intravascular lifespan of ~10 h and a distribution volume of ~10 L, so total body neutrophil turnover is 10.N/10 cells/h, where N is the peripheral blood neutrophil count (cells/litre). Neutrophil loss via the colon in a patient with 50% fecal In‐111 loss is therefore N/120 cells/min. Pan‐colonic mucosal blood flow in pan‐colitis is 200 mL/min, which would deliver N/5 neutrophils to the colon per min. Therefore, 5/120, or 4%, of incoming neutrophils undergo migration into inflamed bowel. If the 96% of non‐migrating cells exit in a primed state, then at steady state >90% of circulating neutrophils would be primed if no de‐priming took place. As the highest level of priming seen in IBD is ~40%, this indicates that de‐priming within the circulation must take place. Using the above values in the steady state equation relating priming rate to de‐priming rate plus primed cell destruction rate gives a mean de‐priming time of 35 min. We conclude that a very small proportion of neutrophils entering a site of inflammation migrate and that in vivo de‐priming must take place to limit the numbers of primed neutrophils in the circulation.

Luminescent-activated transfected killer cells to monitor leukocyte trafficking during systemic bacterial and fungal infection

BACKGROUND

Activated transfected killer (ATAK) cells are immortal phagocytes transfected with a luminescence reporter that effectively treat lethal infections in neutropenic mice. Their in vivo trafficking, lifespan, and immunogenicity are unknown.

METHODS

Mice were made neutropenic; infected or not with Staphylococcus aureus, Acinetobacter baumannii, Candida albicans, or Aspergillus fumigatus; and treated intraperitoneally with ATAK cells. Cell trafficking and lifespan were assessed by in vivo imaging and reverse transcription-polymerase chain reaction.

RESULTS

In uninfected neutropenic mice, ATAK cells spread from the mesentery into visceral organs on days 1-3. Splenic accumulation of ATAK cells increased at day 1 after infection with S. aureus and A. baumannii, and kidney accumulation increased in mice infected with C. albicans. Lung accumulation was seen at day 3 in mice infected by inhalation with A. fumigatus. By day 8, coincident with increasing anti-ATAK antibodies, luminescence signal was lost and there was no detectable mRNA transcription from ATAK cells.

CONCLUSIONS

ATAK cells accumulated in target organs with distinct profiles, depending on the microbial etiology of infection. Finally, generation of an anti-ATAK immune response may provide an important safety mechanism that helps clear the cells from the host as the marrow recovers.

Safety and efficacy of activated transfected killer cells for neutropenic fungal infections

BACKGROUND

Invasive fungal infections cause considerable morbidity and mortality in neutropenic patients. White blood cell transfusions are a promising treatment for such infections, but technical barriers have prevented their widespread use.

METHODS

To recapitulate white blood cell transfusions, we are developing a cell-based immunotherapy using a phagocytic cell line, HL-60. We sought to stably transfect HL-60 cells with a suicide trap (herpes simplex virus thymidine kinase), to enable purging of the cells when desired, and a bioluminescence marker, to track the cells in vivo in mice.

RESULTS

Transfection was stable despite 20 months of continuous culture or storage in liquid nitrogen. Activation of these transfected cells with retinoic acid and dimethyl sulfamethoxazole enhanced their microbicidal effects. Activated transfected killer (ATAK) cells were completely eliminated after exposure to ganciclovir, confirming function of the suicide trap. ATAK cells improved the survival of neutropenic mice with lethal disseminated candidiasis and inhalational aspergillosis. Bioluminescence and histopathologic analysis confirmed that the cells were purged from surviving mice after ganciclovir treatment. Comprehensive necropsy, histopathology, and metabolomic analysis revealed no toxicity of the cells.

CONCLUSIONS

These results lay the groundwork for continued translational development of this promising, novel technology for the treatment of refractory infections in neutropenic hosts.

Neutrophil kinetics in acute bacterial infection. A clinical study

Neutrophil kinetics in peripheral blood were studied with DF32P-labeled cells in eight patients during severe acute bacterial infection. Contrary to previous studies in man, the blood transit time of labeled neutrophils was short and the neutrophil turnover rate increased, up to ten times the normal, during the early phases of infection. This early phase was followed by a period in which the specific neutrophil radioactivity in the blood remained constant for up to 50 hours, probably indicating that in early convalescence neutrophil egress from the bone marrow to the blood is almost stopped. The demonstration of increased neutrophil turnover may seem to illustrate what might be considered an obvious fact, but is in contrast to previous findings and seems to obviate the prevailing theory of quantitatively unchanged but redistributed neutrophil kinetics during bacterial infection in man. The mechanism which apparently abruptly stops neutrophil egress from the bone marrow to the blood during early convalescence is unknown.

The application of a Bayesian approach to the analysis of a complex, mechanistically based model

The Bayesian approach has been suggested as a suitable method in the context of mechanistic pharmacokinetic-pharmacodynamic (PK-PD) modeling, as it allows for efficient use of both data and prior knowledge regarding the drug or disease state. However, to this day, published examples of its application to real PK-PD problems have been scarce. We present an example of a fully Bayesian re-analysis of a previously published mechanistic model describing the time course of circulating neutrophils in stroke patients and healthy individuals. While priors could be established for all population parameters in the model, not all variability terms were known with any degree of precision. A sensitivity analysis around the assigned priors used was performed by testing three different sets of prior values for the population variance terms for which no data were available in the literature: "informative", "semi-informative", and "noninformative", respectively. For all variability terms, inverse gamma distributions were used. It was possible to fit the model to the data using the "informative" priors. However, when the "semi-informative" and "noninformative" priors were used, it was impossible to accomplish convergence due to severe correlations between parameters. In addition, due to the complexity of the model, the process of defining priors and running the Markov chains was very time-consuming. We conclude that the present analysis represents a first example of the fully transparent application of Bayesian methods to a complex, mechanistic PK-PD problem with real data. The approach is time-consuming, but enables us to make use of all available information from data and scientific evidence. Thereby, it shows potential both for detection of data gaps and for more reliable predictions of various outcomes and "what if" scenarios.

Optimization of a myeloid cell transfusion strategy for infected neutropenic hosts

Although granulocyte transfusion is a logical, therapeutic option for neutropenic patients with refractory infections, significant technical barriers have prevented its widespread use. A novel phagocyte transfusion strategy has been developed based on activation of a human myeloid cell line HL-60. To further define the potential for HL-60 cells to recapitulate white cell transfusions, a shortened duration of activation was evaluated, facile quality control markers were defined, and the impact of low-dose irradiation on cell function was determined. Three days of activation resulted in increased cell viability and in vitro candidacidal capacity but with slightly higher cell replication compared with 7 days of activation. Cell viability and several flow cytometric measurements were accurate, quality control markers for HL-60 activation. In combination with activation, low-dose irradiation abrogated replication while sparing the candidacidal effects of the HL-60 cells. Infusion of irradiated, activated HL-60 cells improved survival of neutropenic, candidemic mice significantly. In summary, activated, irradiated HL-60 cells are microbicidal, have virtually no replicative capacity, and are safe and effective at protecting neutropenic mice against an otherwise 100% fatal candidal infection. With continued development, this strategy to recapitulate neutrophil functions has the potential to serve as an effective alternative to granulocyte transfusions.

Enzyme-linked immunosorbent assay for human MRP-8/MRP-14 proteins and their quantitation in plasma of hematological patients

We developed a quantitative enzyme immunoassay for human MRP-8/MRP-14, neutrophil cytosolic proteins with calcium-binding and bacteriastatic properties. MRP-8/MRP-14 concentrations were measured in the plasma of 23 healthy volunteers and in 75 patients with hematological disorders. These proteins were detected in plasma of healthy blood donors with mean +/- standard deviation 167 +/- 114 ng/ml. MRP-8/MRP-14 plasma levels ranged from 435 to 13280 ng/ml in patients with chronic myeloid leukemia (CML), from 50 to 7570 ng/ml in chronic lymphoid leukemia (CLL), from 450 to 2790 ng/ml in polycythemia vera (PV), and were significantly higher than in healthy blood donors (P < 0.01 for CML and P < 0.05 for others). In CML patients MRP-8/MRP-14 levels strongly correlated with total blood WBC count (r = 0.82) and with neutrophilic granulocyte (NG) count (r = 0.80). Correlation of these values in PV amounted to r = 0.70 and r = 0.46, respectively. In CLL patients MRP-8/MRP-14 levels strongly correlated with total WBC count (r = 0.92), but not with the NG count. We suggest that MRP-8/MRP-14 quantitation may serve as a marker of neutrophil pool turnover in some hematological disorders.

Proliferation and maturation of human bone marrow cells in infectious diseases

In 6 patients with various types of infectious disease an extended study of proliferation and maturation of erythropoiesis and granulocytopoiesis was performed. By means of quantitative 14C-autoradiography DNA synthesis time and labeling index were determined in every morphologically defined cell compartment of both lineages. With these parameters and the relative frequency of cells in the various compartments cell cycle times, relative cell production rates and maturation indices were determined. A general labeling index reduction and prolongation of DNA synthesis time was observed which was statistically significant in the majority of compartments. As a consequence, cell cycle times were prolonged throughout, the deviation from normal increasing with advancing maturation in both lineages. Relative cell production was normal in myelocytes, but elevated in myeloblasts and promyelocytes. On the other hand, proerythroblasts and basophilic erythroblasts showed normal relative cell production rates, while a significantly reduced value was found in polychromatic erythroblasts. The maturation index in both lineages was reduced by roughly 50%. Since cell cycle times were generally prolonged, the most significant deviations from normal being present in the latest proliferative compartments, the low maturation indices are discussed in the light of ineffective erythro- and granulocytopoiesis. Premature cell death in the bone marrow is suggested to be a significant factor in particular cases of infectious disease.

Effects of storage and radiation on human neutrophil function in vitro

To better understand the process of time-related functional deterioration which occurs in human polymorphonuclear leukocytes (PMNs), we examined the effects of in vitro storage on multiple functional parameters of human PMNs. Single-donor, phlebotomy-collected PMNs were stored at both room temperature and 37 degrees C for 24 and 48 h, then compared to fresh cells from the same donor. Similar numbers of cells were recovered from each storage condition. Cell viability decreased after 37 degrees C storage for 48 h. Cells stored at room temperature for 24 h showed significant depression of multiple functions (bactericidal activity, chemotaxis, aggregation, superoxide production, and oxygen consumption) compared to fresh cells. They contained less vitamin B12 binding protein activity than fresh cells, and by fluorescence-activated cell-sorter analysis, their forward light scatter and membrane depolarization responses were abnormal. For all parameters examined, cells stored at 37 degrees C were more abnormal than cells stored at room temperature. Stored cells from a patient with myeloperoxidase deficiency lost bactericidal and chemotactic activity after storage at 37 degrees C for 24 h, but cells from a patient with chronic granulomatous disease retained their original bactericidal and chemotactic activity after 37 degrees C storage for 24 h. Radiation, in doses used to prevent graft vs. host disease in leukocyte-transfusion recipients (2500-5000 rads) caused a significant decrease in the mean percentage of continuous flow centrifugation leukapheresis (CFCL) collected PMNs capable of reducing nitroblue tetrazolium. Human PMNs show deterioration of multiple in vitro functions when they are stored and are susceptible to damage by radiation when they are collected by CFCL.

Radiolabeled blood cells: techniques and applications

During the past few years, the clinical and experimental applications of autologous blood cells labeled with gamma-emitting radionuclides, i.e., technetium-99m (Tc-99m) and indium-111 (In-111) have continued to grow rapidly. Investigations have centered around developing techniques that would label blood cells efficiently without alteration of cell viability and their pathophysiologic integrity. Experimental and clinical applications have been aimed at the studies of in vivo cell kinetics and detecting abnormal lesions by external imaging. These will be discussed in detail together with their advantages and disadvantages, and the future directions will be outlined.

Lactoferrin in the myeloproliferative disorders: a search for granulopoietic regulator defects

Evidence of a defect in the negative feedback control of granulopoiesis in the myeloproliferative disorders is presented. Neutrophil release of lactoferrin, plasma lactoferrin concentration, the number of lactoferrin receptor sites on mononuclear cells and granulocyte-monocyte colony stimulating factor (GM-CSF) release from peripheral blood cells were determined in patients with myeloproliferative disorders and compared with normal individuals. There was a significantly (P less than 0.001) decreased release of lactoferrin from the neutrophils of patients with myeloproliferative disorders which could be responsible for a reduced suppression of GM-CSF release from mononuclear cells which in turn may be responsible for the increased myeloid proliferative activity in patients with myeloproliferative disorders.

Labeled cells in the investigation of hematologic disorders

Radiolabeling techniques for white cells, platelets, and erythrocytes are reviewed. The early studies using diisopropylfluoro-32P contributed to an understanding of the production and circulation of the blood elements, and 51Cr proved useful in localizing sites of cell migration or destruction. 111In-oxine has further improved the understanding of blood cell organ sequestration, and permitted combined kinetic and organ imaging studies. Radionuclide labels have been essential for the elucidation of various hematologic disorders, such as the neutropenias, thrombocytopenias, anemias, and polycythemia. Many new treatments, including monoclonal antibodies, have been evaluated with radionuclides.

Asplenia and abnormal neutrophil kinetics in chronic idiopathic neutrophilia

Chronic idiopathic neutrophilia is a rarely recognized finding in otherwise healthy subjects. Described here is a case, not previously reported; in which the patient also had congenital asplenia. Studies carried out to determine the mechanism for the neutrophilia are also described. The results show that the patient's neutrophilia was associated with an enlarged circulating pool of neutrophils, increased production and utilization of neutrophils and a short blood granulocyte survival. The findings differ completely from those observed in patients with chronic idiopathic neutrophilia and intact spleens. The results suggest that (1) the mechanism for neutrophilia in patients with chronic idiopathic neutrophilia varies and depends upon the presence or absence of the spleen, and (2) the spleen has a role in the control of neutrophil production, distribution and utilization.

Neutropenia, inflammation, and the kinetics of transfused neutrophils in rabbits

A rabbit model was used to study the effects of neutropenia and inflammation on the intravascular distribution, survival, and tissue accumulation of transfused neutrophils. Donor blood labeled with [(3)H]thymidine was infused into normal or neutropenic (vinblastine treated) animals. Inflammation was created by subcutaneous implantation of polyvinyl sponges, some with added endotoxin. Initial circulating neutrophil pool recovery, survival, and inflammatory site accumulation of labeled neutrophils were measured. Neutropenia was associated with a relative increase in the marginal pool size, manifested by a diminished initial circulating pool (CNP) recovery of transfused cells. The CNP recovery was directly proportional to recipient neutrophil count. Neutropenia had no effect on the intravascular survival of transfused cells and was accompanied by only a modest decrease in the inflammatory site recovery of the transfused neutrophils (10.4+/-5.4 vs. 14.4+/-4.0% in normals). Inflammation in the form of subcutaneous polyvinyl sponges was accompanied by an increase in margination with initial CNP recoveries of 24.3+/-4.7 and 27.6+/-8.8% at zero and 4 h after implantation respectively (normal, 38.2+/-9.9%). Transit through the CNP was hastened by inflammation with a t((1/2)) of 2.02+/-0.72 h (normal, 3.2+/-1.0 h). Addition of endotoxin to the sponges further perturbed cell kinetics. CNP recoveries were considerably lower and half-lifes were initially shorter and subsequently uninterpretable in studies done after endotoxin sponge insertion. Inflammatory site accumulation was markedly diminished to 7.4+/-1.9% of injected neutrophil label in the endotoxin sponge animals, suggesting that many of the transfused cells were functionally unavailable rather than marginated. These studies demonstrate that neutropenia and inflammation with or without endotoxin markedly alter the kinetics of transfused neutrophils and that CNP recovery of transfused cells is not necessarily predictive of their inflammatory site accumulation.

Blood colony-forming cells (CFU-C) and leucocyte colony-stimulating activity (CSA) in patients with neutrophilic leucocytosis

The incidence of circulating colony-forming cells (CFU-C) and the ability of peripheral leucocytes to stimulate the colony formation (CSA) have been studied through a double layer agar culture system in 26 patients with neutrophilic leucocytosis and compared to the values obtained in 26 normal subjects. Both mean CFU-C incidence and mean leucocyte CSA of the whole group of patients were found significantly higher than normal, but considerable variation was observed among singular patients. The different patterns of blood CFU-C and leucocyte CSA are discussed. The combined evaluation of blood CFU-C and leucocyte CSA is found a useful tool to investigate the pathogenetic mechanisms of neutrophilic leucocytosis.

The measurement of granulocyte kinetics

Studies using 3H-TdR, DF32P or 51Cr have all contributed important information concerning neutrophil kinetics in normal and abnormal conditions. Recent evidence, however, suggests that DF32P underestimates, and 51Cr overestimates, the blood neutrophil T1/2 and that both isotopes overestimate the TBNP, compared with 3H-TdR-derived data. The differences are quantitative and not qualitative, and the principles of blood neutrophil kinetics defined by DF32P studies are still valid. 3H-TdR studies are impractical for general use, and clinical measurement of neutrophil kinetics will have to continue to rely on the use of either DF32P or 51Cr. Comparison of abnormal findings with normal values obtained using the same isotope is probably valid for either technique. Changes in neutrophil kinetics leading to a neutrophil leucocytosis in different situations are fairly predictable from published data. In neutropenias, however, kinetic studies might be needed to delineate the relative contributions of under-production, shortened survival and excessive margination in the individual patient.

[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.

Neutrophil marrow release. A system analysis

Neutrophil marrow egress is governed by several processes. The most important are cell maturation, functional behavior of marrow sinusoids and humoral or neuro-vascular factors. Neutrophil release cannot be observed directly but is reflected in the size, cellular composition and kinetics of the nonproliferating pool of granulocytopoiesis in bone marrow and of blood neutrophil pool. These experimentally determined parameters were used as the basis of a mathematical model study. The model describes two catenated compartments, the nonproliferating pool of granulocytopoiesis in marrow and the total blood granulocyte pool. Cell transit from one pool to the other was assumed to be age-dependent. It was expressed by a positive sloping sigmoidal function that defines the egress potential fo the cells that increases with cell maturation. During maturation granulocytopoietic cells develop intense motility which determines the morphology of the cells on smears. Relationship between cell motility and its morphology was defined by functions determining the age-dependent probabilities of cell fixation as metamyelocytes, band- and segmented forms, respectively. The parameters of this model could be so adjusted that all experimental data were matched within experimental errors. Thus, qualitative and quantitative information on neutrophil marrow egress was obtained for normal and pathological states of granulocytopoiesis.

Leukaemoid reactions in myeloproliferative diseases. Report of two patients

The occurrence of transient extreme neutrophilic leucocytosis, with white blood cell counts exceeding 100,000/mu-l in two adult patients with myeloproliferative diseases, polycythaemia vera and acute myelocytic leukaemia in remission, is reported. The reaction was transient, and the subsequent course of the patient's disease did not differ from that prior to the episode. Such extreme leucocytosis is rare in adults, despite the frequency of provoking conditions, and factors which predispose an individual to develop a leukaemoid reaction remain unknown. An increase in the size of the pool of proliferating granulocyte precursors accompanied by a loss of the restraining function of the marrow sinusoidal walls in myeloproliferative diseases may explain the augmented release of myeloid cells in our patients.

The cytokinetics of monocytosis in acute salmonella infection in the rat

The mechanisms responsible for monocytosis occurring in acute Salmonella infection were studied by means of isotopic labeling and autoradiography. Male (Lewis x BN)F(1) hybrid rats (160-180 g) were pulse-labeled with [(3)H]TdR at varying intervals with respect to the time of i.v. injection of about 10(6) living Salmonella enteritidis. The half time for monocytes in the blood was estimated from the exponential decline in the percentage of labeled monocytes. The average generation time for dividing monocyte precursors in bone marrow was estimated by fitting a regression line to the decline in median grain counts (halving-time = T(G)). After an initial fall, the absolute number of blood monocytes rose to a plateau about 2.5 x normal on day 5, suggesting the reimposition of steady state conditions. The half time of monocytes in the blood of infected rats was shortened to 25 h throughout the infection, compared with 61 h estimated in uninfected rats. T(G) was reduced to 15 h (days 1-3) but later reverted to the preinfection level of 34 h (days 4-8). Another early response to infection was the release of immature monocytes into the blood. These cells, however, were too few to offset the initial monocytopenia. Under these conditions, with little or no division of blood monocytes, the sustained monocytosis (days 4-8) must have been due to enlargement of the dividing precursor pool. Excessive loss of monocytes from the blood thus appears to activate a feedback mechanism. However, a more direct stimulating effect on monocyte production by endotoxin could have contributed substantially to the monocytosis.

Periodic hematopoiesis in human cyclic neutropenia

Human cyclic neutropenia is characterized by severe depression of blood neutrophil levels approximately every 21 days. To investigate the mechanism of cyclic neutropenia four patients were studied with daily complete blood counts, serial bone marrow examinations, marrow reserve testing, serum muramidase determinations, DF(22)P granulocytokinetic studies, and, in one patient, in vivo [(3)H]TdR labeling. Periodogram analysis of the serial blood counts in the latter patient and visual inspection of multiple cycles in the others revealed periodic fluctuations in the levels of blood neutrophils, monocytes, lymphocytes, reticulocytes, and platelets. Rhythmic changes in the morphologic and radioisotopic studies as well as the marrow reserve tests and muramidase measurements were consonant with a mechanism of periodic failure of marrow production rather than peripheral destruction. Human cyclic neutropenia is analogous to cyclic neutropenia in the grey collie dog and may be viewed as the consequence of cyclic hematopoiesis.

Leukokinetic studies. 13. A non-steady-state kinetic evaluation of the mechanism of cortisone-induced granulocytosis

The mechanism by which adrenocortical steroids induce granulocytosis in man has been investigated using granulocytes labeled with radioactive diisopropylfluorophosphate. After an intravenous injection of 200 mg of cortisol was given to five normal subjects, the mean value for the total blood granulocyte pool increased from 79 to 138 x 10(7) cells per kg of body weight and reflected an increase in the size of both the circulating granulocyte pool and the marginal granulocyte pool. When granulocytes in the circulation were labeled with diisopropylfluorophosphate and granulocytosis was induced later by the intravenous administration of cortisol, the rate of decline of granulocyte specific activity was increased, indicating that the blood pool was being diluted at an accelerated rate by unlabeled cells entering from the bone marrow. The rate of egress of granulocytes from the blood pool to an inflammatory exudate was studied by the "skin window" technique. After the administration of cortisol, there was a mean reduction in the cellularity of induced inflammatory exudates of 75%. However, this reduction in cellularity varied considerably from subject to subject (45-98%). From these studies we can infer that steroids induce an absolute granulocytosis by decreasing the rate of egress of cells from the total blood granulocyte pool as well as by increasing the influx of cells from the bone marrow. By model simulation studies of the non-steady state induced by cortisol injection, it has been possible to quantitate these rate changes. In the present studies cortisol injection resulted in a mean decrease in blood granulocyte egress of 74% (1-99%) and a mean increase in cell inflow of 450% (300-750%).

Neutrophil kinetics in acute infection

Neutrophil kinetics of acute experimental infection were studied with diisopropylfluorophosphate-(32)P labeling in 31 dogs inoculated intrabronchially with pneumococci. In vitro neutrophil labeling indicated a rapid transit time through the blood in early infections, with an elevated marginal granulocyte pool sometimes preceding an elevation of the circulating granulocyte pool. 13 hr after infection, the circulating and total blood granulocyte pools were increased but the rate of neutrophil transit through the blood was normal. During the recovery from infection there was a marked prolongation of neutrophil blood transit time, suggesting virtually complete cessation of bone marrow release of neutrophils into the blood. Labeling of neutrophils in vivo indicated an increased rate of emptying of the bone marrow storage pool proportional to the severity of infection as measured by the fever index. The change in the blood ratio of nonsegmented to segmented neutrophils was a much more accurate index of the severity of infection than the blood granulocyte concentration, correlating significantly with the fever index.