The effect of glucocorticosteroids on the kinetics of mononuclear phagocytes

Comparison of the development of experimental pyelonephritis in homozygous brattleboro diabetes insipidus rats, heterozygous control rats and normal Wistar rats

A comparative study was performed on haematogenous experimental pyelonephritis by injecting a Staphylococcus aureus suspension i.v. to homozygous and heterozygous Brattleboro and Wistar rats. The numbers of viable bacteria in blood, urine and kidney homogenates and the pathomorphological scores determined on the tenth day of infection were significantly lower in Brattleboro diabetes insipidus rats than in heterozygous Brattleboro and normal Wistar rats. The results suggest that homozygous Brattleboro rats are much more resistant to experimental pyelonephritis.

Method to select mice in the steady state for biological studies

Collection of small amounts of blood from the orbital sinus was found to be a satisfactory method for repeated sampling in mice, which means that these animals can be selected for further study on the basis of the leukocyte count. In biomedical research it is often necessary to have detailed information about the effect of injected material on the numerical course of circulating leukocytes. However, the present study has shown that 2 stress-producing procedures on 1 day disturb the steady state, and that this disturbance is expressed in changes in the number of leukocytes. Such stress could be avoided by alteration of the experimental design to include only 1 stressful situation each day. When blood was sampled in the orbital sinus on 1 day to determine the animals' condition and on the next day only the tail was punctured as sham injection, the number of blood leukocytes remained constant throughout the observation period. Comparative studies on the numbers of monocytes, lymphocytes, and granulocytes in blood from the tail, heart, and orbital sinus showed a systematic difference in the mean numbers of certain types of leukocytes. Statistically significant differences were found between the mean numbers of monocytes, lymphocytes, and granulocytes in orbital blood from normal mice of 5 specific pathogen-free strains, i.e., Cpb:SE (Swiss), CBA/Cpb, BALB/cCpb, C3H/Rij, and DBA/2Rij.

A comparison of the effects of hydrocortisone on peritoneal inflammatory exudates, the tuberculin reaction and contact sensitivity-to DNFB in the guinea pig

Hydrocortisone acetate, injected subcutaneously in five doses in a depot producing vehicle, causes prolonged suppression of the ability of guinea pigs to produce a chronic inflammatory reaction in the peritoneal cavity and also of the tuberculin reaction. This suppression of the tuberculin reaction persists for at least 65 days after the last dose of hydrocortisone. Suppression of both peritoneal exudate and the tuberculin reaction was associated with a preferential depletion of macrophages at the reaction site. A similar regime had no effect on the ability of guinea pigs to manifest contact sensitivity reactions to 2,4-dinitrofluorobenzene although there was a similar drop in macrophages in the lesion. It appears that the effect of hydrocortisone on delayed hypersensitivity reactions is not directly related to the functional contribution of macrophages in the inflammatory reactions, and may be related to the site of the inflammatory reaction in the skin.

Dual origin of mouse spleen macrophages

The present study concerns the isolation, characterization, origin, and kinetics of spleen macrophages. The spleen was first perfused in situ to remove monocytes from the vascular bed and then dissected and treated with collagenase. The macrophages in the cell suspension thus obtained were characterized morphologically and cytochemically and then quantitated. The spleen cell suspension was incubated for 24 h in Leighton tubes to obtain an enriched glass-adherent population of macrophages for characterization and [3H]thymidine-labeling studies. Almost all of the adhering macrophages were esterase positive, had Fc and C3b receptors, and ingested EIgG and opsonized bacteria. In vitro labeling with [3H]thymidine showed that approximately 5% of the mononuclear phagocytes in the spleen synthesize DNA and must be considered to be dividing cells. The course of the number of labeled monocytes and macrophages after a single injection of [3H]thymidine indicates migration of monocytes into the spleen, where they become macrophages. Calculation of the influx of monocytes into the spleen and of the local production of macrophages by DNA-synthesizing mononuclear phagocytes showed that under steady-state conditions, 55% of the population of spleen macrophages is supplied by monocyte influx and 45% by local production. This means that there is a dual origin of spleen macrophages. The mean turnover time calculated with the value for the efflux of spleen macrophages is 6.0 d.

Differential effects of steroids on leukocyte-mediated glomerulonephritis in the rabbit

The effects of steroids on the development of injury in two models of experimental glomerulonephritis (GN), (one mediated by neutrophils, the other by macrophages) were compared. The neutrophil-associated lesion [initiated by heterologous antiglomerular basement membrane (GBM) antibody] was characterized by the development of an exudative endocapillary GN with heavy neutrophil accumulation [mean, 6.9 neutrophils/glomerular cross section (N/GCS) +/- 2.9 SD], minor macrophage infiltration [7.9 macrophages/glomerulus (M/G) +/- 2.2 SD] and heavy proteinuria (1905 mg/24 hr +/- 520 SD). Steroid-treated (methylprednisolone, 2 mg/kg/12 hr i.v.) rabbits developed a marked monocytopenia, mild neutrophilia, and significant reduction in glomerular macrophage accumulation (0.3 M/G 0.02 SD). However, neutrophil accumulation (6.1 N/CGS +/- 2.5 SD), histological appearances, and proteinuria (1820 mg/hr +/- 490 SD) were unaffected. The macrophage-associated model of GN was induced by passive autologous rabbit anti-sheep IgG 15 hr after the injection of a subnephritogenic dose of the same anti-GBM antibody. The glomerular lesion was characterized by a diffuse endocapillary proliferative GN with heavy macrophage infiltration (54 M/G +/- 8 SD), insignificant neutrophil accumulation (0.8 N/GCS 0.02 SD), and the regular development of proteinuria (420 mg/24 hr +/- 80 SD). Steroid-treated rabbits developed a mild neutrophilia and a significant monocytopenia associated with abrogation of glomerular macrophage accumulation (2.3 M/G +/- 0.8 SD). This was associated with the prevention of the development of GN and proteinuria (22 +/- 9.5 SD). Thus, steroids produce monocytopenia and prevent glomerular macrophage accumulation and associated injury whereas neutrophil accumulation and injury is unaffected. These data suggest steroids may have widely varying effects on the outcome of leukocyte-associated experimental GN depending on the nature of the infiltrating cells.

Glucocorticoids modulate macrophage surface oligosaccharides and their bone binding activity

The circumstantial evidence that indicates that glucocorticoids (GC) may stimulate osteoclastic resorption in vivo has recently found support in observations that demonstrate that these compounds effectively increase the activity of isolated resorptive cells (osteoclasts, macrophage polykaryons, and elicited macrophages [MO] ) in vitro. Data are presented here that indicate that this stimulation by GC is due to an enhancement of the initial stage of the resorption process, the attachment of cells to bone, and that this is caused by alterations of cell surface oligosaccharides. Specifically, dexamethasone and cortisol enhance by 80% the attachment of MO to bone surfaces in a dose dependent manner but do not alter or reduce the binding of these cells to other surfaces (plastic, collagen, and hydroxyapatite crystals). The effect of GC on cell-bone attachment is blocked by the glycosylation inhibitor, tunicamycin, and the glycosylation modifier, swainsonine; this demonstrates that asparagine-linked oligosaccharides are involved in the stimulatory process. Flow cytometric analysis of GC-treated cells using a panel of fluoresceinated lectins confirms this by indicating a selective, enhanced exposure of plasma membrane-associated N-acetylglucosamine and N-acetylgalactosamine residues, sugars we have previously shown to be pivotal in MO-bone binding. Finally, progesterone, a known GC antagonist, blocks GC-stimulated resorption, macrophage-bone binding, and membrane oligosaccharide modification, presumably by competing for the GC receptor. Progesterone alone alters none of these processes. Thus, GC stimulates the resorptive activity of macrophages by enhancing the initial events in the degradative process (cell-bone binding) and does so, apparently, via receptor-mediator alteration of cell surface glycoproteins.

Babesia hylomysci and Babesia microti: dexamethasone treatment of infected mice

The effect of dexamethasone on Babesia hylomysci and B. microti was investigated in LACA mice. The drug enhanced both infections by depressing the immune mechanisms of the host when treatment was initiated before parasite inoculation, but had no effects on established and subpatent infections. The degree of parasitemia in the treated mice seemed to depend on the tropism of either parasite toward mature erythrocytes or reticulocytes. B. hylomysci, which favors mature erythrocytes, produced fulminating infections in treated mice. B. microti, which prefers reticulocytes, produced similar parasitemia patterns in treated and untreated mice, but only the treated mice succumbed to the infection. The drug, which suppressed cellular proliferation in the spleens of infected animals, together with its direct lympholytic effects, drastically changed the architecture of the organ.

The correlation between plasminogen activator activity and thymidine incorporation in mouse bone marrow-derived macrophages. Opposing actions of colony-stimulating factor, phorbol myristate acetate, dexamethasone and prostaglandin E

Plasminogen activator activity and [3H]thymidine incorporation were studied in mouse bone marrow-derived macrophages. The two activities correlated closely in the presence of stimulatory (colony-stimulating factor, phorbol myristate acetate, PMA) and inhibitory (dexamethasone, prostaglandin E1) signals. The actions of dexamethasone and prostaglandin E1 could be overcome by either stimulatory agent, so that the net effect was an alteration in sensitivity of the macrophages to colony-stimulating factor, or PMA. The sensitivity of bone marrow-derived macrophages to CSF-1 was also reduced by the addition of small numbers of CSF-1 unresponsive peritoneal macrophages. Plasminogen activator induction was not a sufficient signal for [3H]thymidine incorporation which requires an additional macromolecular serum component. The serum component was found not to be plasminogen.

Effects of methylprednisolone on the Fc-receptor function of human reticuloendothelial system in vivo

To determine whether the Fc-receptor function of reticuloendothelial system (RES) is modified by corticosteroid administration, we studied the spleen to liver uptake ratios of autologous, 99Tc-labelled heat-damaged or IgG-coated erythrocytes, injected intravenously into 10 normal volunteers, 4 h after receiving a single dose of 32 mg of methylprednisolone by mouth. In standard conditions, quantitative scans indicated that the spleen to liver uptake ratios, calculated per unit area 40 min after the injection of labelled erythrocytes, were 13.4 +/- 0.6 and 31.2 +/- 1.5 (mean values +/- -SEM), for the heat-damaged (n = 7) and IgG-coated red cells (n = 5) respectively. Four hours after corticosteroid administration, the spleen to liver uptake ratios were significantly reduced in five of ten volunteers. Abnormal ratios correlated with the Fc-receptor function of monocytes measured in vitro using IgG-coated erythrocytes. Indeed, 2-6 h after methylprednisolone was given, the Fc-receptor binding activity of monocytes isolated from the same five subjects was reduced by at least 50%, spontaneously returning to a rather normal value 4-6 h later. The C3-receptor binding activity of these monocytes remained normal, after otherwise identical experimental conditions. These results show a transient, specific impairment of the Fc-receptor function of RES after methylprednisolone administration, and may therefore explain, in part, the infectious complications occurring in some patients treated by corticosteroids.

Effect of hydrocortisone on the macrophage content, growth and metastasis of transplanted murine tumors

Hydrocortisone (HC) reduced the macrophage content of four murine tumors to less than half of control values. Since HC causes monocytopenia and inhibits the recruitment of mononuclear phagocytes at sites of inflammation but does not affect the viability and proliferative capacity of macrophages, this finding suggests that the maintenance of macrophage levels in growing tumors is in part dependent upon the entry into the neoplasm of circulating monocytes. HC inhibited the growth of these tumors. The effect of HC was most marked on the mFS6 and MN/MCA1 sarcomas and 3LL carcinoma, with only marginal inhibition in the M109 carcinoma. HC augmented spontaneous and/or artificial (i.v.) metastasis in these tumor models. Cells from metastatic foci of the mFS6 sarcoma and M109 carcinoma inoculated i.m. were as susceptible to HC as cells from primary tumors. The effects of HC on macrophage content, growth and metastasis of the M109 carcinoma and mFS6 sarcoma were similar in mice with defective T-cell function (nude or thymectomized) or defective NK activity (beige or antiasialo GM1-treated) and in controls. The in vitro growth of the mFS6 and MN/MCA1 sarcomas was not modified by HC. Some inhibition of tumor-cell proliferative capacity was observed with the 3LL and M109 tumors. Tumor cell had high-affinity binding sites for glucocorticoid hormones, but these were not correlated to susceptibility in vivo. Thus it is unlikely that a direct interaction of HC with tumor cells accounts for the inhibition of tumor growth observed in vivo. To evaluate whether HC affected tumor growth by reducing the macrophage content of tumors, mFS6 sarcoma cells were transplanted, mixed with peritoneal macrophages into normal or HC-treated mice. Macrophages did not affect the growth of tumor cells in normal mice, whereas in HC-treated animals lesions from mixtures of macrophages and sarcoma cells appeared earlier and weighed more than those from tumor cells alone or tumor cells and thymocytes. However, macrophages did not reconstitute growth of the other sarcoma (MN/MCA1) in HC-treated mice. These results are consistent with the hypothesis that HC inhibited growth of some poorly immunogenic transplanted murine tumors, at least in part, by interfering with the macrophage levels in neoplastic tissues, tumor-associated macrophages providing the conditions for optimal tumor-cell proliferation at least in some neoplasms.

Origin and kinetics of resident tissue macrophages. Parabiosis studies with radiolabelled leucocytes

To elucidate the origin and renewal kinetics of peritoneal macrophages, as a typical example of the mononuclear phagocytic system, syngeneic rats were treated with tritiated thymidine [3H]TdR and leucocytes were transferred to unlabelled recipients over a bilateral arteriovenous shunt. Labelled and unlabelled monocytes were evenly distributed in both animals as shown by autoradiography. It was ascertained that no 'autoradiographically' detectable reutilization of label occurred and that transferred cells showed undisturbed kinetics. The results imply: resident peritoneal macrophages derive from blood monocytes; peritoneal macrophages represent a homogeneous population in respect to their cellular origin; blood monocytes as a myelogenous cell line do not represent a generative end cell. They migrate into the tissue (peritoneal cavity) and differentiate into resident macrophages, undergoing on average one mitosis per cell during a period of approximately 7 days. resident peritoneal macrophages are derived 50% from blood monocytes and 50% from division in situ; and under steady-state conditions the renewal rate amounts to 0.18%/h, which yields a half-life time of 16 days and a renewal time of 23 days.

The function and structure of granulocytes collected using the IBM 2997 separator

The effect of oral methylprednisolone and the sedimenting agent, hydroxyethyl starch, on granulocyte recovery, morphology, and function was studied in a volunteer donor programme. Using the IBM 2997, 10 litres of whole blood were processed, with an average procedure time of 2.4 hours and a collection volume of 300 ml. Donors not receiving methylprednisolone (n = 80) had a mean total granulocyte count of 3.5 X 10(9)/litre (range 1.6-5.3 X 10(9)/litre) and mean granulocyte yields were 1 X 10(10) (range 0.2-3.0 X 10(10)). Those receiving 48 mg oral methylprednisolone 6-8 hours before the procedure (n = 320) had a mean granulocyte count of 6.3 X 10(9)/litre (range 3.2-11.4 X 10(9)/litre) and significantly superior mean granulocyte yields of 2.0 X 10(10) (0.3-6.5 X 10(10)) (P less than 0.05). For both groups the mean packed cell volume of 0.08 litre/litre (range 0.02-0.17) and platelet contamination 1.9 X 10(11) (range 0.3-5.0 X 10(11)). In all these procedures, hydroxyethyl starch was added to the blood entering the centrifuge channel. In none of the procedures were any untoward symptoms experienced by the donors. Light microscopy and ultrastructural studies showed no difference between control granulocytes and those collected following the addition of hydroxyethyl starch or after oral methylprednisolone. Similarly, granulocyte function measured with a random migration, chemotaxis, phagocytosis, and intracellular killing was not significantly different between control cells and those exposed to the sedimenting agent or the adrenocorticosteroids (P greater than 0.10). It is concluded that donor premedication with methylprednisolone significantly enhances granulocyte yields in the presence of hydroxyethyl starch and neither agent has any demonstrable effect on granulocyte morphology or function.

Effect of prednisolone in vitro on the migration ability of peritoneal macrophages in rats

Prednisolone in vitro decreases the random migration of peritoneal macrophages in non-sensitized rats. In sensitized animals cells are sensitive or resistant to prednisolone's inhibitory action, depending on the presence of antigen in the culture.

Apoprotein E is synthesized and secreted by resident and thioglycollate-elicited macrophages but not by pyran copolymer- or bacillus Calmette-Guerin-activated macrophages

Macrophages are active secretory cells that display functionally distinct phenotypes that are regulated by inflammation. We have found that apoprotein E (ApoE), a component of plasma lipoproteins, was synthesized and secreted by resident and nonspecifically stimulated macrophages elicited with thioglycollate broth, but not by activated macrophages obtained from mice treated with bacillus Calmette-Guerin, pyran copolymer, whole Corynebacterium parvum, or bacterial endotoxin. ApoE represented approximately 1% of the newly synthesized protein and approximately 10% of secreted protein of resident and thioglycollate-elicited macrophages. ApoE from thioglycollate-elicited macrophages was indistinguishable from ApoE in mouse plasma lipoproteins, as determined by immunoreactivity, peptide mapping, and molecular weight. When specific antibodies were used to localize cell-associated ApoE, strong immunofluorescence was seen in the Golgi region of resident and thioglycollate-elicited macrophages immediately after removal from the peritoneal cavity, as well as after culture for up to 7 d. In contrast, activated macrophages did not synthesize or secrete ApoE to an appreciable extent and had no immunocytochemically detectable intracellular ApoE. When activated macrophages were cultured in medium containing serum, their activated state, as judged by production of H2O2, declined within 48-72 h in parallel with the induction of synthesis and secretion of ApoE and detection of intracellular ApoE by immunofluorescence. During prolonged culture the rate of synthesis and secretion of ApoE increased in both resident and activated macrophages. Therefore, the synthesis and secretion of ApoE may serve as markers for the functional state of macrophages.

Pulmonary tissue and cigarette smoke. 2. Parenchymal response

Cigarette smoke and hydrocortisone acetate (HCA) induce marked abnormalities in lungs of C57BL/6J male mice. In many pulmonary regions of smoke-exposed, HCA-treated animals, alveoli were highly congested with surfactant and flocculent material. In addition, prominent alveolar collapse and septal hypertrophy were common. These conditions resembled pulmonary alveolar proteinosis described in humans. Administration of HCA to sham-treated animals also produced lung abnormalities, however, considerably milder in severity, while stress (resulting from sham treatment) or HCA injections of mice alone failed to induce any pulmonary tissue disorder. Data reported indicate that the genesis of abnormal conditions which resemble pulmonary alveolar proteinosis is potentiated by cumulative effects of different treatments (i.e., smoke, HCA, and stress), most significant being the interaction between cigarette smoke and the steroid.

Modulation of expression of epidermal Langerhans cell properties following in situ exposure to glucocorticosteroids

Langerhans cells (LC) have been implicated as antigen-presenting and target cells in contact allergic, cell-mediated reactions. We have examined the effects in guinea pigs, rats, and humans of in situ (epicutaneous) exposure to glucocorticosteroids (GCS) on the expression of epidermal LC markers. Reductions in the number of Fc-rosetting, C3b-rosetting, and immune-associated (Ia) antigen-bearing LC occurred in a dose-related fashion, with the degree of such reductions dependent upon the specific GCS employed. These reductions were determined to be reversible following cessation of exposure to GCS. T6 antigenicity, another cell surface marker of human LC, was little affected by GCS exposure. Simultaneous immunofluorescent staining for T6 and Ia antigenicity within human epidermis of amcinonide treated skin detected reduced numbers of T6+/Ia+ cells with a concomitant increase in T6+/Ia- cells. The data presented suggest a selective reduction in the expression of immunologically important receptors and antigens by LC which may be involved in steroid-responsive contact allergic reactions.

Effect of dexamethasone on serum transcobalamin II concentration in women undergoing pelvic surgery

Dexamethasone (120 mg/day for 2 days) was administered intramuscularly to young females undergoing pelvic surgery for infertility. The therapy was shown to cause a transient increase in the serum level of the granulocyte-produced transcobalamins (TCI and TCIII) and more significantly in the monocyte-produced transcobalamin (TCII), from 1220 +/- 70 to 1980 +/- 158 pg/ml (P less than 0.001). The change closely followed a transient elevation of EA rosette forming cells in the peripheral blood (from 20 to 50% of the total mononuclear cell population), which are mainly monocytes. The observed effects were shown to be independent of the surgical trauma. The results indicate that the increase in serum TCII can be attributed to an effect of dexamethasone on monocytes.

[Immunopharmacology of corticosteroids]

Immunopharmacological effects of corticosteroids are primarily dependent upon their capacity to modify inflammatory reactions at various levels. Their molecular effects are related to the vascular system and to lymphocytes, phagocytes and mast cells, all cell types being involved in inflammation. They modulate the physiology, molecular biology and membrane dynamics of these cells thereby influencing cellular and humoral immune functions. The complexity of these effects may at least partially explain the usefulness of corticosteroids in cases of immunoproliferative, autoimmune and allergic disorders.

The current view on the origin of pulmonary macrophages

In the present contribution the current view on the origin of macrophages is briefly summarized. Recent studies on the kinetics of pulmonary macrophages in the normal steady state and during an inflammatory reaction induced by heat-killed BCG applied intravenously or by aerosol are reported in more detail, and the effect of glucocorticosteroids on the kinetics of these cells is described. The results support the general conclusion that pulmonary macrophages derive mainly from circulating monocytes, exclude the existence of an interstitial pool of dividing precursors cells, and provide evidence that the limited local production of pulmonary macrophages is the result of division of mononuclear phagocytes recently derived from the circulation.

In vitro assessment of immune function in adrenalectomized rats

Spleen and lymph node cells from normal or adrenalectomized (Adx) rats were assessed for a variety of in vitro immunological measures, including mitogen responsiveness, antibody-dependent cellular cytotoxicity (ADCC), and natural killer (NK) cell activity. Proliferation in response to mitogens was evaluated with or without 2-mercaptoethanol (2-ME) in the culture media. Compared to spleen cells from normal rats, those from Adx rats demonstrated enhanced responsiveness to all mitogens tested. 2-ME increased proliferation of spleen cells from both normal and Adx rats, and the effect was additive to that of adrenalectomy. In contrast, lymph node cells from Adx rats manifested decreased mitogenic responsiveness compared to those of control rats and, with the addition of 2-ME, this difference disappeared for one of the mitogens tested (phytohemagglutinin). Compared to unoperated rats, ADCC and NK activities were significantly decreased in both the spleen and lymph nodes of the Adx rats. Alteration of normal leukocyte circulatory and homing patterns are suggested as a likely means by which adrenalectomy produces differential effects on lymphoid cells in various organs of the immune system.

Coxsackievirus B infection in pregnant mice and transplacental infection of the fetus

Direct instillation of coxsackievirus B1 into the gastrointestinal tracts of albino mice caused viremia in more than 85% of the animals within 1 day. In pregnant mice infected early in gestation (7 days), the geometric mean titer of virus in the blood was lower (P = 0.02) and the duration of viremia was shorter (P = 0.07) than in nonpregnant female mice, but infection of the heart, liver, and uterus did not differ on each of 5 days after infection. Although transplacental infection of the placenta or fetus or both occurred, the high spontaneous abortion rate (48%) obviated comparison of transplacental infection in these mice with mice infected later in gestation. Pregnant mice infected in the third trimester had significantly greater geometric mean titers of virus in the blood, heart, liver, and uterus, and infection persisted longer than in nonpregnant mice (P = 0.04). A very high geometric mean titer of virus was recovered from the uteri of these mice for 3 days after infection, whereas simultaneous geometric mean titers of virus in the placentas and fetuses were lower. In the majority of third trimester pregnant mice, virus was found in low titers in the fetuses at 2 and 3 days after maternal infection, and virus was not detected after day 3. We conclude that coxsackievirus B1 infection in late gestational pregnant mice is more severe than in mice at earlier gestational stages and in nonpregnant mice and that transplacental infection of the fetus occurs transiently during maternal infection. This model will prove useful in the study of perinatal enterovirus infection and in examination of the numerous factors that may influence outcome of infection of perinatally infected newborn infants.

Influence of cortisone on amoeboid microglia and microglial cells in the corpus callosum in postnatal rats

Amoeboid microglia and typical microglial cells in the corpus callosum of rats were studied following a subcutaneous injection of cortisone at birth. The rats were killed 2, 5, 10 and 20 days after the injection. The most striking change in the corpus callosum was the great reduction in the number of amoeboid microglial cells as shown by the silver carbonate stain of Rio-Hortega. The change was sustained throughout the period studied. Ramified and typical microglial cells which do not normally appear until between the fifth and tenth postnatal day, were observed on the second postnatal day after the cortisone administration. Cell enumeration in semithin sections showed that the proportion of amoboid microglial cells was reduced to 50% of their normal value soon (2 days) after the cortisone injection. This proportion was further decreased and the cells were absent from the fifth postnatal day onwards. Typical microglial cells were developed prematurely and they constituted more than 2% of the total glial population 2 days after the cortisone injection. Another striking change noted in the semithin section was the increase in the compactness of the axons in the corpus callosum in the experimental animals. Electron microscopic observations were in general agreement with the light microscopy. The amoeboid microglial cells appeared less active; they contained small Golgi apparatus, accumulations of lipid droplets and sparse lysosomes. The cell outline was regular. The reduction in the number of amoeboid microglia after the cortisone injection was explained by the fact that the drug suppressed the production of their precursor cells, i.e. circulating monocytes, Moreover, it was suggested that cortisone probably interfered with the phagocytic activity of the amoeboid microglial cells which would normally undergo structural changes to become the quiescent microglia which were observed in the early postnatal animals.

Molecular basis of fever in humans

This review presents several areas of research on the pathogenesis of fever in humans and updates new information concerning the role of fever in host defense mechanisms. Fever is mediated by a polypeptide of phagocytic cell origin called leukocytic pyrogen. Several agents and disease processes are associated with the synthesis and release of leukocytic pyrogen. Although the original studies on leukocytic pyrogen suggested that the neutrophil was the primary source, recent experiments indicate the mononuclear phagocyte to be the major producer of leukocytic pyrogen. The mechanism by which human monocytes are stimulated to produce leukocytic pyrogen is discussed, including the effects of corticosteroids, estrogens and antipyretics on the synthesis of leukocytic pyrogen in vitro. The ability of leukocytic pyrogen to alter the hypothalamic thermoregulatory center by increasing arachidonic acid metabolite levels is the most likely mechanism by which leukocytic pyrogen initiates fever. Antipyretics prevent the synthesis of certain cyclooxygenase metabolites, which accounts for their ability to reduce fever. Studies on the chemical and physical properties of human leukocytic pyrogen are reviewed and form the basis for current experiments on the similarities between leukocytic pyrogen and lymphocyte activating factor. These studies suggest that leukocytic pyrogen, in addition to producing fever, also stimulates non-hypothalamic cells involved in aspects of the acute-phase response. In this regard, leukocytic pyrogen may be an important mechanism for host defenses. Hyperthermia may also be beneficial to the host but is distinct from fever; the role of leukocytic pyrogen as well as hyperthermia as a defense mechanism is discussed.

The effect of epicutaneous glucocorticosteroids on human monocyte and neutrophil migration in vivo

The effect of epicutaneous methyl prednisolone (MP) at 10-4, 10-5, and 10-6 molar concentration was studied in 54 normal, healthy volunteers using a new, in vivo microchemotaxis technique. Significant inhibition of monocyte chemotaxis occurred at all concentrations studied and persisted over a 24-hr period with 10-4 molar MP. Neutrophil chemotaxis was significantly inhibited only with 10-4 MP. The inhibitory effect of MP on neutrophil and monocyte chemotaxis occurred earlier and at lower concentrations if the skin sites were pretreated with steroid. Thus, when corticosteroids are applied on abraded skin in concentrations achievable in vivo, monocyte chemotaxis into tissue is inhibited for longer periods and at lower drug concentrations than is neutrophil chemotaxis. By avoiding the significant systemic effects of corticosteroids on circulating monocyte and neutrophil populations, these experiments establish that local inhibition of chemotaxis is an important anti-inflammatory effect of corticosteroids, with differential effect on monocytes and neutrophils.

Prednisone-induced leukocytosis. Influence of dosage, method and duration of administration on the degree of leukocytosis

The long-term pattern of prednisone-induced leukocytosis was examined in 80 patients. Our results disclosed an extremely variable leukocytic responses, in which the white blood cell count surpassed 20,000/mm3 as early as the first day of treatment, an increase that persisted for the duration of therapy. Although the degree of leukocytosis was related to the dosage administered, it did appear sooner with higher doses. Leukocytosis reached maximal values within two weeks in most cases, after which the white blood cell count decreased, albeit not to pretreatment levels. The leukocytosis was attributed predominantly to a rise in the polymorphonuclear white blood cells, a phenomenon that coincided with monocytosis, eosinopenia and a variable degree of lymphopenia. It can be concluded that even small doses of prednisone, administered over a prolonged period of time, can induce extreme and persistent leukocytosis. This observation is of consequence especially when infection is suspected, particularly in an immunocompromised host. However, a shift to the left in the peripheral white blood cells, i.e., more than 6 percent band forms, and the appearance of toxic granulation may assist in the differential diagnosis between infection, in which the latter are observed, and corticosteroid-induced leukocytosis, in which they are rare.

Effect of betamethasone on fetal macrophage function: depression of adherence of immunoglobulin-coated red blood cells

In this study, betamethasone was found to significantly inhibit the binding of immunoglobulin-coated O Rh-positive red cells to fetal macrophages. At a dose of 0.15 mg%, betamethasone depressed immune rosette formation to 44% of controls (p less than 0.01); and a dose of 0.60 mg% resulted in an average depression to 22%. This in vitro effect may reflect important alterations in in vivo immune function in infants delivered from mothers who have received antenatal corticosteroids.

Origin and kinetics of pulmonary macrophages during an inflammatory reaction induced by intravenous administration of heat-killed bacillus Calmette-Guérin

This report gives a quantitative description of the kinetics of the pulmonary macrophages and their direct precursors during the acute inflammatory reaction in the lungs induced by intravenous injection of heat-killed bacillus Calmette-Guérin (BCG) into specific-pathogen-free mice. After BCG injection, the total number of pulmonary macrophages isolated by lavage and subsequent enzyme digestion of lung tissue increased to 225% of normal within 12 h and, after a minor decrease, rose to a maximum of 250% of normal at 96 h, followed by a decrease to 150% at 144 h, the end of the observation period. The number of circulating monocytes doubled in the first 48 h and stayed close to that level. In vivo and in vitro labeling with [3H]-thymidine showed that an influx of monocytes transforming into pulmonary macrophages was mainly responsible for the population increase. A temporary increase in the number of locally dividing pulmonary macrophages--manifested by an increased in vitro labeling index, reaching a maximum of 9.6% 72 h after BCG injection--made a minor contribution to the population increase. All pulmonary macrophages were classified according to morphological criteria as alveolar-macrophage-like (AML) or non-alveolar-macrophage-like (NAML), and their respective characteristics were established. The in vivo labeling data showed NAML to represent exudate macrophages derived from circulating monocytes entering the interstitial tissue, and these cells changed morphologically into AML upon entering the alveolar hypophase. This mechanism was confirmed by the finding that the interstitially deposited BCG were found first inside NAML and later in AML. The in vivo labeling data showed that local production was mainly a result of division of macrophages that were morphologically identical with normal alveolar macrophages. The former cells, however, derived most probably recently from the circulation, because the turnover of the total population was very high before local macrophage production became maximal. In mice treated with HC before the injection of BCG, this population increase was absent, because of virtual abolition of the initial monocyte influx and absence of the increased local production of macrophages. Calculations showed that the monocyte influx in the first 48 h amounted to approximately 4 x 10(6) cells, i.e., eight times that found in the normal steady state, and that the efflux of pulmonary macrophages in that period amounted to approximately 3.5 x 10(6) cells, i.e., seven times the normal efflux. The local production over the total period of 144 h was only three times that found normally. The results of these quantitative studies show that the increase of the pulmonary macrophage population during an acute inflammation is brought about mainly by monocyte influx and to a minor extent by a temporary increased local production of macrophages. Disposal of interstitially deposited BCG occurred by phagocytosis by local macrophages and the subsequent efflux of the latter.

Viral myocarditis. A review

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Serum levels of hepatitis B surface and core antigens during immunosuppressive treatment of HBsAg-positive chronic active hepatitis

One of the following treatments was randomly assigned to 101 consecutive patients with biopsy-proven chronic active hepatitis: prednisone 20 mg daily, azathioprine 100 mg daily, prednisone 20 mg and azathioprine 50 mg daily, or B vitamins 2 tablets daily (control group). Patients were observed at the beginning of the study, then at 2, 6, and 12 months after treatment. At each visit levels of HBsAg and Dane-particle-associated core-antigen (HBcAg) and their corresponding antibodies were determined. 42 patients were HBcAg positive at the beginning of the study. Of these 42 patients, the 34 who were under treatment remained HBcAg positive and showed a rise in HBcAg titre, while the 8 who were not treated had a fall in HBcAg titre (6 patients) or became HBcAg negative (2 patients) in 6 months. Among 59 patients who were HBcAg negative at the beginning of the study, this antigen became persistently detectable in 40% of the 42 patients who were treated, and was transiently present in 2 (12%) out of the 17 untreated patients (p < 0.05). Our data indicate that long-term prednisone and/or azathioprine treatments favour the replication of hepatitis-B virus in patients with HBsAg-positive chronic active hepatitis.

The response of bone marrow cells, thymocytes and osteoclasts to hydrocortisone

Hydrocortisone injections in young rats caused an increase in the proliferative response of bone marrow cells but a disintegration of thymus gland, the cells of which probably disappeared from thymus. Earlier investigations have shown that different kinds of trauma and antigen result in an increase in the mitotic rate of bone marrow and thymus cells and at the same time an increase in the number of osteoclasts. After steroids, however, no increase of osteoclasts occurred, probably because monocytes which develop into osteoclasts and macrophages are inhibited by hydrocortisone. The effect on serum calcium was minimal.

Prevention of the immunosuppressive effects of glucocorticosteroids by cell-free factors from adjuvant-activated accessory cells

Cultured mouse spleen cells are protected from the immunosuppressive effects of glucocorticosteroid hormones by prior treatment with bacterial adjuvants. The mechanisms by which such protection is acquired were further invgestigated in this study. Cell-free factors, termed glucocorticosteroid response modifying factors (GRMF), were obtained from the supernatant fluid of normal resident murine peritoneal macrophages activated in vitro by treatment with lipopolysaccharide. These factors provided protection against steroid immunosuppression in a dose dependent fashion. Two-step experiments show that GRMF treatment results in the recovery of significant amounts of T helper activity which otherwise is suppressed by steroids. Factors with similar biologic activities were also obtained from murine monocytic cell lines. The possible mechanisms by which GRMF protects the immune response are discussed.

Late results of the Royal Free Hospital prospective controlled trial of prednisolone therapy in hepatitis B surface antigen negative chronic active hepatitis

A long-term follow-up of at least 10 years or until death of 44 patients taking part in a controlled prospective trial of prednisolone therapy in hepatitis B antigen negative chronic active hepatitis (lupoid hepatitis) has been performed at the Royal Free Hospital, London. Patients presenting between 1963 and 1967 were randomly allocated into control and treatment groups. Ten year life table survival curves showed a significantly improved survival in the treatment group where 63% of patients were alive at 10 years compared with only 27% in the control group (log rank test, P = 0.03). The median survival in the treatment group was 12.2 years compared with 3.3 years in the control group. The mean duration of treatment was 4.5 years. Age, presence of antinuclear factor, cirrhosis, or level of serum transaminases at presentation did not appear to affect survival. Male patients if untreated had a poorer prognosis than females (P = 0.02). The natural history of chronic active hepatitis appeared from clinical, biochemical, and histological findings to be from an active hepatitis or cirrhosis to inactive macronodular cirrhosis. Prednisolone therapy significantly improved survival by reducing mortality in the early active phase of the disease.

The antinflammatory effects of glucocorticosteroids. A brief review of the literature

The effects of glucocorticosteroids on immune and inflammatory responses are reviewed. The steroids seem to change the number or function of cell receptors for regulating agents, so that in areas of inflammation: (a) blood vessels dilate less, (b) lymphocytes proliferate less, (c) all leukocytes infiltrate less, (d) macrophages become less activated (digesting and secreting less), and (e) fibroblasts produce less collagen and ground substance. In addition, the corticosteroids seem to alter the response of cells to various signals from their receptors by affecting the prostaglandin system, cyclic nucleotides, and perhaps other internal mediators.

Origin, Kinetics, and characteristics of pulmonary macrophages in the normal steady state

Pulmonary macrophages of mice in the steady state were isolated by lavage with PBS containing EDTA and subsequent enzymatic digestion of tissue with pronase and DNA-ase. By this method, the total pulmonary macrophage population was obtained in two cell suspensions, one with a pure population of pulmonary alveolar macrophages (PAM) and the other with a mixed population of pulmonary alveolar and pulmonary tissue macrophages (PTM). The morphological, cytochemical, and functional characteristics of both PAM and PTM were like those of mature tissue macrophages except for the presence of C3 receptors. These receptors were almost absent on PAM and present on a larger number of cells in the mixed population of PAM and PTM. The total pulmonary macrophage population of mice in the steady state is approximately equal to 2 x 10(6), of which about 93% are PAM and about 7% are PTM. In labeling experiments with 3H-thymidine, the low in vitro labeling indices (less than 3%) for both PAM and the mixture of PAM and PTM, showed that both are essentially nondividing cells. In vivo labeling studies showed an increase in the number of labeled macrophages that can only be attributed to labeled monocytes migrating into the lungs. Additional evidence was provided by a decrease in the labeling indices of pulmonary macrophages when mice were treated with hydrocortisone acetate, which causes a severe monocytopenia, thus preventing monocyte influx into the lungs. Confirmation of the bone marrow origin was obtained in mice labeled after x-irradiation with partial bone marrow shielding: labeled pulmonary macrophages were found in the exposed lungs. In all experiments, the labeling indices were identical in the two macrophage populations isolated. These results show that the influx of monocytes is the source of cell renewal for the pulmonary macrophages. No indications for an interstitial division or maturation compartment in the lung were found. Quantitation of the efflux of labeled monocytes from the blood, and the number of labeled pulmonary macrophages, showed that in the steady state about 15% of the monocytes leaving the circulation become pulmonary macrophages and that the turnover time of pulmonary macrophages is approximately equal to 27 d.

Further studies on mobilization of CFUs

Mobilization of CFUs from haemopoietic tissues into circulation was studied after injection of different bacterial lipopolysaccharides (LPS), zymosan, phytohaemagglutinin (PHA), concanavalin A (Con A), trypsin and di-isopropyl-fluorophosphate-inhibited trypsin. All bacterial LPS used gave an increase of CFUs in the peripheral blood at 1 h after i.v. injection. Some variation in activity could not be excluded. As with Salmonella typhosa LPS, zymosan gave an increase in circulating CFUs during the first few hr and a second peak a few days later. After injection of zymosan as well as S. typhosa LPS the second peak in the blood was accompanied by a large increase in CFUs numbers in the spleen. PHA gave an immediate mobilization of CFUs, but the mobilization after injection of Con A during the first few hr occurred more slowly. After injection of S. typhosa LPS, zymosan and PHA the blood C3 level was found to be depressed considerably. This might indicate that the complement system is involved in the early mobilization of CFUs. Dexamethasone, a synthetic hormone which has been reported to give sequestration of several cell types in the bone marrow, did not inhibit the early and late mobilization of CFUs which normally occurs after injection of S. typhosa LPS.

Origin and kinetics of Kupffer cells during an acute inflammatory response

The course of the increased number of liver macrophages and the origin of these cells were studied after intravenous stimulation by zymosan, stilboestrol, or corynebacterium. The macrophages were isolated by digestion of the liver with pronase and DNAase.

Zymosan doubled the number of liver macrophages per gram of liver and led to a four- to five-fold increase in the number of blood monocytes, whereas stilboestrol induced a four-fold increase of liver macrophages and a two-fold increase of blood monocytes. Corynebacterium administration gave a two-fold rise in the number of liver macrophages and a six-fold increase of blood monocytes.

The in vitro labelling index of the liver macrophages showed a transient but marked increase after the administration of zymosan or stilboestrol, but returned to approximately normal values 4 days after the stimulus. Hydrocortisone given 48 h before zymosan prevented this increase in the in vitro labelling index of liver macrophages, thus demonstrating that the mononuclear phagocytes labelled in vitro had recently been recruited from the bone marrow to the liver.

Stimulation by stilboestrol or zymosan of mice labelled with [³H]-thymidine caused an increase in the number of labelled liver macrophages and blood monocytes as compared with the numerical course of the labelled Kupffer cells and monocytes in untreated mice. It may be concluded that this increase is attributable to the increased influx into the circulation of labelled monocytes from the bone marrow, which in turn migrate to the liver in larger numbers than are seen in the normal steady state. Local proliferation could not have been responsible for the increased number of labelled liver macrophages, because free [³H]-thymidine was no longer available when the stimulus was applied. Evidence supporting the bone marrow origin of the increased number of monocytes and liver macrophages after intravenous stimulation was provided by the course of the number of monocytes and liver macrophages in hydrocortisone-treated mice given zymosan as stimulus.

Regulation of the immune response by macrophages

Regulation of the immune response by macrophages was studied with cellular resistance to Listeria monocytogenes as parameter. The use of agents which suppress macrophage activity during the induction-phase of immunity enabled the induction of protective immunity with killed listeria. Fractionation of the cell content of listeria yielded an RNA'se sensitive fraction which in a dose of 300 ng and in combination with the cationic surfactant dimethyl dioctadecyl ammonium bromide induced protective immunity against listeria.

Differential response of early erythropoietic and granulopoietic progenitors to dexamethasone and cortisone

The sensitivity of erythropoietic (BFU-E) and granulopoietic (CFU-C) progenitor cells to dexamethasone and cortisone was studied in cultures of mouse bone marrow. Although the log dose-response relationships had a similar form, the BFU-E were much more sensitive than the CFU-C to either glucocorticoid. The dexamethasone concentration for 50% inhibition was 3 X 10)-9) M for BFU-E and 60 X 10(-9) M for CFU-C. The differential sensitivity to cortisone was even greater, with 60% inhibition of BFU-E and 18% inhibition of CFU-C at 0.1 microgram/ml. These findings suggest a specific rather than a general response to glucocorticoids and indicate that granulocyte-macrophage progenitors are less affected than early erythroid progenitors by physiologic concentrations of these hormones.