Destruction of sensitized erythrocytes by human monocytes in vitro: effects of cytochalasin B, hydrocortisone and colchicine

Canine idiopathic thrombocytopenic purpura

Canine idiopathic thrombocytopenic purpura (ITP) is a disease in which antibodies bound to the surface of platelets mediate premature platelet destruction by macrophages. ITP in dogs and chronic ITP in humans are analogous diseases. This article draws on information from the literature on ITP in dogs and in humans, and reviews the pathogenesis, diagnosis, and treatment of ITP in dogs.

Protection against immune haemolytic disease of newborn infants by maternal monocyte-reactive IgG alloantibodies (anti-HLA-DR)

The extent to which maternal anti-Rh(D) antibodies support lysis of erythrocytes by monocytes in the antibody-dependent cell-mediated cytotoxicity (ADCC) assay is closely correlated with the severity of Rh(D) haemolytic disease of the newborn infant (HDN). However, in some cases HDN is much milder than would be predicted from the ADCC value. We postulated that maternal ADCC-blocking alloantibodies against paternal antigens on monocytes can protect these infants against severe haemolysis. We studied 13 severely Rh(D)-alloimmunised mothers whose infants showed unexpectedly mild HDN (group I) and 14 women with similar ADCC values but whose infants had severe HDN (group II). 7 group-I women had monocyte-reactive IgG alloantibodies that inhibited lysis by paternal monocytes in the ADCC. No such antibodies were found in group II (p less than 0.01). In 6 of the 7 serum samples with monocyte-reactive antibodies, the antibodies had HLA-DR specificity. Our findings suggest that Rh(D)-positive children of some severely Rh(D)-alloimmunised women may be protected from severe HDN by maternal non-HLA-class-I, IgG alloantibodies against paternal monocyte blood-group antigens. These antibodies may inhibit the mononuclear phagocyte system of the fetus.

Activity of two types of Fc receptors, Fc gamma RI and Fc gamma RII, in human monocyte cytotoxicity to sensitized erythrocytes

We investigated the cytotoxicity of human monocytes mediated by two types of receptors for the Fc portion of IgG, Fc gamma RI and Fc gamma RII. Erythrocytes sensitized with human IgG (EA-human IgG) were used to assay Fc gamma RI function, and erythrocytes sensitized with mouse IgG1 (EA-mouse IgG1) were used to assay Fc gamma RII. Both types of Fc gamma R were observed to mediate antibody-dependent cell-mediated cytotoxicity (ADCC), which was further characterized by using different monoclonal anti-Fc gamma R antibodies (MoAb) and monomeric IgG. Lysis of EA-human IgG was inhibited by both monomeric human IgG and mouse IgG2a in a dose-dependent way, and also by anti-Fc gamma RI MoAb 10.1. Cytolysis of EA-mouse IgG1 was inhibited by monomeric mouse IgG1 and by two anti-Fc gamma RII MoAb, IV.3 and CIKM5. Antibodies of the mouse IgG2b isotype affected neither type of ADCC. The effectiveness of cytotoxicity mediated by either of the Fc gamma R was studied by means of targets sensitized with a calibrated number of IgG molecules. At least 20 times more IgG molecules per target cell were necessary to obtain half-maximal cytotoxicity mediated by Fc gamma RII than for Fc gamma RI-mediated cytolysis. Furthermore, the previously described polymorphism of Fc gamma RII was also reflected in Fc gamma RII-dependent cytotoxicity. These studies demonstrate that Fc gamma RII can mediate ADCC, although a higher degree of target cell sensitization is required than for Fc gamma RI-mediated ADCC.

Inhibition of natural killer cell-mediated cytotoxicity by ML-9, a selective inhibitor of myosin light chain kinase

To investigate the role of microfilaments in natural killer (NK) cell-mediated cytotoxicity, general microfilament inhibitors, cytochalasins B,D and dihydrocytochalasin B, and a selective inhibitor of myosin light chain kinase (MLCK) which regulates microfilament contraction, i.e. 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML-9) were examined in an NK assay system. ML-9 inhibited NK cell activity in a dose-dependent manner without affecting target cell binding, whereas cytochalasins suppressed the binding. The dextran suspension method revealed that ML-9 inhibits the programming for the lysis stage of the lytic process. In the single cell assay, the addition of ML-9 after target cell binding had occurred inhibited the lysis of bound target cells, whereas the addition of cytochalasins in a similar manner did not affect it. Thus, these results suggest the possibility that microfilament contraction is involved in the lytic mechanism of NK cell-mediated cytolysis. However, the mechanism whereby cytochalasins inhibit target cell binding remains unclear.

Effect of anticancer drugs on macrophage-mediated antibody-dependent cytotoxicity and secretion of reactive oxygen intermediates

The in vitro effects of methotrexate, vincristine, dexamethasone and adriamycin to modulate the antibody dependent cellular cytotoxicity (ADCC) reaction and secretion of superoxide (O2-) and hydrogen peroxide (H2O2) by phorbol myristate acetate (PMA) stimulated rat peritoneal macrophages were studied. Macrophage-mediated ADCC, as measured by the lysis of 51Cr-labeled IgG-coated sheep red blood cells in an 18 h assay, was significantly enhanced in the presence of 100 ng/ml of PMA. Treatment of macrophage monolayers for 24 h with vincristine (10(-5)-10(-7) M), dexamethasone (10(-5)-10(-9) M) and adriamycin (10(-6) M) inhibited ADCC by PMA stimulated macrophages. Vincristine, dexamethasone and adriamycin also inhibited the secretion of O2- and H2O2 by PMA stimulated macrophages at similar concentrations that reduced the ADCC reaction. Methotrexate (10(-3)-10(-7) M) did not inhibit either ADCC or O2- and H2O2 secretion by PMA stimulated macrophages. These results suggest that select anticancer drugs can inhibit macrophage mediated cytotoxicity of antibody coated target cells by suppressing the release of reactive oxygen intermediates by activated macrophages.

Different requirements for the induction of antibody-dependent and immune complexes triggered cytotoxicity mediated by monocytes

We have previously shown that immune complexes triggered nonspecific cytotoxicity (NSC) towards nonsensitized target cells and antibody-dependent cellular cytotoxicity (ADCC), two functions mediated through monocyte Fc gamma receptors, employing different lytic mechanisms [Geffner, J. R., et al. (1986) Clin. Exp. Immunol. 67, 646]. In this report, we analyze some of the metabolic requirements involved in the induction of monocyte NSC and ADCC. The results showed NSC to be dependent on: (1) metabolic energy derived from glycolysis, (2) availability of external Ca2+, (3) calmodulin activity, (4) integrity of microtubules, but not the microfilament system, and (5) activation of phospholipase(s) and lipoxygenase. On the other hand, ADCC was not impaired by: (1) inhibition of glycolysis, (2) Ca2+ chelation, (3) disruption of microtubules, or (4) inhibition of calmodulin or lipoxygenase. It is concluded that monocyte NSC and ADCC are regulated by different endogenous signals.

Intravascular hemolytic transfusion reaction without detectable antibodies: A case report and review of literature

A case of intravascular hemolytic transfusion reaction without detectable antibodies occurring in a 55-year-old male is reported. Specificity for the C antigen in the Rh system was demonstrated by technetium-99m red cell survival studies. A cell-mediated mechanism of hemolysis was suspected and investigated. Previously reported cases are reviewed and discussed. The entity of intravascular hemolytic transfusion reaction associated with minimal symptoms and no detectable antibodies deserves further investigation.

Antibody-dependent cell-mediated cytotoxicity and phagocytosis of autologous red blood cells in alphamethyldopa-induced haemolysis

7 alphamethyldopa (AMD)-treated patients with positive direct antiglobulin test (DAT) were investigated. Peripheral blood mononuclear phagocytes of 2 patients suffering from haemolysis caused lysis and phagocytosis of autologous DAT-positive red blood cells (RBC). Eluates from RBC of both patients contained antibodies of IgG1 subclass and supported antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent phagocytosis (ADPh) of the patients' RBC after remission. Both cytotoxic activities were proportional to the serum concentration and to the number of attacking cells. The 5 patients without overt haemolysis did not show in vitro lysis or phagocytosis of autologous RBC. These results suggest that ADCC as well as ADPh participate in the destruction of RBC in AMD-induced haemolysis in vivo.

Autoimmune hemolysis: a critical review

Autoimmune hemolysis is defined as a shortening of erythrocyte lifespan due to antibodies directed against the individuals own red cells. This autoantibody production (by B lymphocytes) is thought to result from deficient activity of suppressor T lymphocytes. The rate of erythrocyte destruction depends on the properties of the autoantibodies and on the activities of the complement and mononuclear phagocyte systems: anemia results when destruction outweighs marrow production. Autoimmune hemolysis, which may be primary or secondary, is classified into "warm," "cold," and "mixed" types. The hemolysis associated with pregnancy. Donath-Landsteiner antibodies, of mixed type, and in children, is treated in detail. Current treatment is with immunosuppressive drugs, surgery, and plasma exchange, though immunomanipulation may become important in the future; blood transfusion may be a life-saving adjunct to other therapy.

Mechanisms of lysosomal enzyme secretion by human monocytes

Secretion of lysosomal enzymes by human monocytes in response to various stimuli and the effect of conditioned media from lymphocytes and neutrophils was studied. Monocytes were found to release beta-glucosaminidase in response to NH4Cl and to particles (zymosan, opsonised zymosan, asbestos and latex), but do not respond to some soluble stimuli like formyl-methionyl-leucyl-phenylalanine, phorbol myristate acetate, cytochalasin B, concanavalin A and N-acetylmuramyl-L-alanyl-D-isoglutamine. Neutrophil conditioned medium or neutrophil components did not have any effect on secretion. When treated with lymphokines the cells are more responsive, especially to zymosan. Even through there are similarities in the secretory activities of mouse macrophages and human monocytes, there are several differences both in the quantity of the response and in the mechanisms involved.

Effect of corticosteroids on neutrophil function: inhibition of antibody-dependent cell mediated cytotoxicity (ADCC)

Hydrocortisone sodium succinate (HC) inhibited "in vitro" neutrophil-mediated antibody-dependent cellular cytotoxicity (ADCC). The drug effect was dose-dependent and completely reversible. The killing defect was partially overcome by increasing the density of the antibody on the target cells. However, HC added after the binding between effector and target cells was still able to inhibit in a similar dose-dependent way the cytotoxic activity. Our results suggest that HC interferes in a later step, after the effector/target interaction. Methyl-prednisolone and dexamethasone as well as HC were found to inhibit in a dose-dependent manner the neutrophil-mediated ADCC, whereas testosterone did not have any effect.

Colchicine in generalized pustular psoriasis: clinical response and antibody-dependent cytotoxicity by monocytes and neutrophils

Four patients with generalized pustular psoriasis were treated with oral colchicine in an open study. Three of the four patients went into total remission within two weeks while receiving colchicine. The monocyte- and neutrophil function was assessed by studying antibody-dependent cytotoxicity. Increased values observed before treatment decreased during treatment. The patient who responded poorest clinically also showed less changes in monocyte- and neutrophil antibody-dependent cytotoxicity.

Divergent effects of methylxanthines and adenylate cyclase agonists on monocyte cytotoxicity and cyclic AMP levels

The effects of theophylline, isobutylmethylxanthine (IBMX), prostaglandin E1 (PGE1), and isoproterenol on monocyte antibody-dependent cytotoxicity (ADCC) were compared with their effects on monocyte cyclic adenosine 3':5'-monophosphate (cAMP) levels. Theophylline (2 mmol/l) halved ADCC and gave a 2-fold increase in cAMP levels. At concentrations not elevating cAMP theophylline inhibited ADCC significantly. In comparison, incubation of monocytes with IBMX, PGE1 and isoproterenol ADCC was only modestly inhibited while these agents gave larger increments (3- to 8-fold) in cAMP levels than theophylline did. Low concentrations of IBMX (50 mumol/l) elevated cAMP without affecting monocyte ADCC whereas PGE1 and isoproterenol inhibited ADCC dose-dependently comparable to increases in cAMP. However, in doses giving similar inhibition of ADCC addition of PGE1 resulted in larger cAMP increments than isoproterenol. The effects of IBMX, PGE1 and isoproterenol was dependent on target cell to effector cell ratio and increased during preincubation with the agents. The inhibition of ADCC by the agents was accompanied by a depressed monocyte lysozyme release and depressed activation of hexose monophosphate shunt. However, only theophylline affected monocyte attachment to sensitized target cells. These results argue against the general inverse relationship between cAMP content and inhibition of monocyte ADCC and demonstrate that theophylline independent on increases in cAMP inhibits ADCC probably by abrogation of monocyte binding activity.

Simultaneous detection of two mechanisms of immune destruction of penicillin-treated human red blood cells

Two separate processes of putative red-cell destruction in penicillin-induced immune hemolysis were measured simultaneously by a rapid (3 hour) assay utilizing 51Cr-labelled red blood cells (RBC). Antibody-dependent, cell-mediated cytotoxicity (ADCC) was estimated by release of 51Cr; and antibody-dependent phagocytosis (ADPh) by quantitation of 51Cr uptake into mononuclear phagocytes as well as by counts of engulfed RBC. Attacking cells were obtained by Ficoll-Hypaque separation of peripheral blood from normal donors. Phagocytosis as well as lysis were proportional to anti-penicillin antiserum concentration, to incubation time, and to the concentration of the attacking cells. Enrichment of mononuclear phagocytes in the attacking cell population by albumin gradient separation led to an increase in phagocytosis as well as in cytotoxicity. Depletion of mononuclear phagocytes resulted in a decline in both processes. Dilution of antiserum abolished ADCC but affected ADPh only slightly. Iodoacetate as well as colchicine inhibited both activities. These results indicate that both processes may be operative in the immune destruction of RBC in vivo.

Activation of monocyte and granulocyte antibody-dependent cytotoxicity by phorbol myristate acetate

We have characterized the effects of phorbol myristate acetate (PMA) on human monocyte and neutrophil oxidative metabolism and antibody-dependent cytotoxicity toward anti-D sensitized human erythrocytes (RBC) and a human lymphoblastoid cell line (CEM). Hexose monophosphate shunt activity was measured by [1-(14)C]glucose oxidation and target lysis by (51)Cr release. PMA produced a dose-dependent stimulation of hexose monophosphate shunt activity. Neutrophils responded with higher hexose monophosphate shunt activity and at a lower PMA concentration than did monocytes. PMA increased monocyte lysis of antibody-sensitized RBC by two-thirds, but did not affect lysis of CEM targets. Neutrophils were unable to lyse either antibody-sensitized or nonsensitized RBC without the addition of PMA. When PMA was added, lysis of both targets increased markedly. Neutrophils without PMA were able to lyse a small number of both antibody-sensitized and nonsensitized CEM targets. PMA also increased neutrophil lysis of these targets. Target lysis by neutrophils from a patient with chronic granulomatous disease, cells unable to produce reactive oxygen species, was not increased by PMA. Chronic granulomatous disease monocytes, however, responded to PMA by more than doubling lysis of antibody-sensitized RBC. Hypoxia inhibited PMA augmentation of antibody-sensitized RBC lysis by neutrophils, but not by monocytes. Generation of reactive oxygen species by the xanthine-xanthine oxidase system inhibited CEM growth, but did not cause lysis, indicating that in some cases oxidative injury may be nonlytic. We suggest that PMA augments neutrophil cytotoxicity to tumor and RBC targets by stimulating reactive oxygen species-mediated lysis, but in monocytes augmentation of lysis is due to activation of a nonoxidative mechanism of lysis.

Male-female differences in the cytotoxic activity of human monocytes in vitro

The cytotoxic activity of human monocytes towards anti-D-sensitized Rh(D)-positive red cells in vitro was studied in relation to the age and sex of healthy monocyte donors. It was found that cytotoxic activity of monocytes from young females (age range 18-40 years) was significantly less than that of monocytes from age-matched males, irrespective of the use of oral contraceptives. No such difference was found between monocytes from older males and females (age range 43-63 years). The cytotoxic activity of monocytes from the two latter groups of donors was similar to that of young males. In the presence of cytochalasin B, which enhances the cytotoxic activity of monocytes, no male-female difference was detected, indicating that the maximal cytotoxic capacity of monocytes from young females is similar to that of monocytes from young males. We have previously presented evidence that the cytotoxic activity of monocytes is mediated by lysosomal enzymes released by these cells. These present data suggest that the reduction in cytotoxic activity of monocytes from young females might be a result of a reduced lysosomal enzyme release which is possibly related to the in vivo action of female sex hormones. However, we were not able to detect an inhibitory effect of oestrogens and progestagens on cytotoxic activity of monocytes from males in vitro.

Isolation of large numbers of highly purified lymphocytes and monocytes with a modified centrifugal elutriation technique

A modified centrifugal elutriation technique is described for the isolation of large numbers of lymphocytes and monocytes. Elutriation was carried out by lowering the rotor speed at a constant flow rate which was generated by hydrostatic pressure. The flow rate could be kept constant if the separation procedure was performed at high pressure and high systemic resistance. Up to 2.3 X 10(9) mononuclear cells derived from 2000 ml blood were separated in one single experiment in approximately 1 h. The lymphocytes and monocytes were isolated at purities of 98 +/- 1% and 94 +/- 1% respectively. The purity of the lymphocytes was increased to 99.8 +/- 0.1% by a second elutriation run. Additional advantages of the elutriation procedures are that the choice of medium is free, and that relatively large numbers of cells may be separated with high recoveries.

Role of oxygen in antibody-dependent cytotoxicity mediated by monocytes and neutrophils

The antibody-dependent cell-mediated cytoxicity (ADCC) by human monocytes and neutrophils was investigated by measuring the release of 51chromate from prelabeled erythrocytes coated with immunoglobulin G. ADCC was found to be positively correlated to phagocytosis of 51Cr-labeled erythrocytes and to the postphagocytic events of the effector cells, activation of the hexose monophosphate shunt, and degranulation. Exclusion of oxygen from the incubation media halved the ADCC by both cell types without affectijg phagocytosis or degranulation. Likewise, ADCC by cells from patients suffering from chronic granulomatous disease (CGD) was only half the intensity of ADCC by cells from normals. Inhibitors of mitochondrial respiration were without depressing effect of ADCC. Azide, which in addition to its blocking action on oxydative phosphorylation also inhibits catalase and myeloperoxidase, resulted in a approximately equal to 40% stimulation of ADCC by cells from normals but was without effect of ADCC by cells from CGD patients. The hydroxyl radical scavenger, mannitol, significantly depressed ADCC by cells from normals (P < 0.01) but was without effect on cells from CGD patients. Azide and mannitol also were without effect on ADCC by normal cells when oxygen was excluded. In a xanthine-xanthine oxidase system, erythrocytes were effectively lysed. This lysis was inhibited by catalase, superoxide dismutase, and mannitol. When comparable concentrations of glucose oxidase were used no lysis was observed. H2O2 either alone or in combination with azide did not lyse erythrocytes. It is suggested that ADCC by both monocytes and neutrophils is partly dependent on the generation of hydroxyl radicals by the effector cells.

Impaired monocyte-mediated cytotoxicity in atopic dermatitis

Twenty-three adult patients with atopic dermatitis of different severity and extent all without present cutaneous infection were investigated for antibody-dependent cytotoxicity mediated by purified monocytes. Compared to a healthy control group the monocyte cytotoxicity was significantly decreased for patients with more widespread dermatitis. Eight patients with acute contact dermatitis and 13 patients with extrinsic asthma or allergic rhinitis showed normal cytotoxicity. Decreased monocyte cytotoxicity in atopic dermatitis was not related to the serum IgE level. In vitro cultivation of defective monocytes from atopics did not increase cytotoxicity, nor did normal monocytes preincubated with patient serum show abnormal function. In atopic dermatitis the total number of Fc receptor bearing monocytes was normal. However, the affinity of this receptor was lower than in normals. Serial studies are needed to establish whether reduced monocyte function is a basic pathophysiologic defect in atopic dematitis.

Quantitative aspects of the destruction of red cells sensitized with IgG1 autoantibodies: an application of flow cytofluorometry

The purpose of this study was to determine whether quantitative or qualitative factors are of major importance in the destruction of red cells sensitized with incomplete warm autoantibodies of subclass IgG1. To that end, the relative amount of igG1 antibody present on the red cells of patients with autoantibodies of this subclass only, was measured by means of continuous flow cytofluorometry. This method appeared to give an idea of the amount of antibody on red cells and was reproducible. The intensity of the fluorescence of patient's red cells, measured after incubation with a FITC-labelled anti-IgG1, was compared with the presence or absence of signs of increased haemolysis in vivo and the cytotoxic activity of normal monocytes towards these red cells in vitro. It appearedthat it was predominantly the amount of IgG1 autoantibody that determined whether or not these antibodies induced haemolysis in vivo or cytotoxicity of monocytes in vitro. This was also true with methyldopa-induced IgG1 autoantibodies.

Role of oxygen-dependent mechanisms in antibody-induced lysis of tumor cells by activated macrophages

The alloantiserum-dependent lysis of TLX9 lymphoma cells by peritoneal cells from Bacille Calmette-Guerin (BCG)-treated mice was inhibited 62 percent by depletion of oxygen. This effect did not appear to be a result of interference with mitochondrial respiration because cyanide, azide, and dinitrophenol did not inhibit cytotoxicity. Preincubating the effector cells for 2 h without glucose, which markedly reduces their ability to release hydrogen peroxide, likewise suppressed antibody-dependent cytolysis by 62 percent. Lysis of sensitized lymphoma cells was virtually abolished by 6 mg/ml of thioglycollate broth, a concentration that also abrogated the detectable release of hydrogen peroxide and the lysis of lymphoma cells by BCG-activated macrophages in response to phorbol myristate acetate (PMA). This concentration of thioglycollate broth was not toxic to the effector cells, as judged by adherence to plastic, binding of opsonized erythrocytes, and phagocytosis of radiolabeled starch granules. Catalase, superoxide dismutase, horseradish peroxidase, mannitol, ethanol, benzoate, and diazabicyclooctane were without consistent effects. Cytochalasin B and dihydrocytochalasin B both markedly suppressed cytolysis, whether induced by antibody or by PMA (ID(50), 0.5 mug/ml). Cytoehalasin B was an equally potent suppressor of glucose uptake and PMA-induced hydrogen peroxide release by BCG-activated macrophages (ID(50), 0.5 mug/ml). However, dihydrocytochalasin B lacked these latter effects, which suggests that cytotoxicity required intact contractile elements. The extracellular lysis of antibody-coated lymphoma cells by BCG-activated macrophages appears to have a predominantly oxidative basis.

Mechanisms of antibody-dependent cellular cytotoxicity: the use of effector cells from chronic granulomatous disease patients as investigative probes

The present study characterized the antibody-dependent cellular cytoxicity (ADCC) of leukocyte effector cells (neutrophils, lymphocytes, and monocytes) from normal subjects and from chronic granulomatous disease (CGD) patients. CGD phagocytic cells (neutrophils and monocytes) had depressed ADCC activity against antibody-coated human erythrocyte (HRBC) targets in suspension cultures indicative of abnormal intracellular postphagocytic killing. However, when phagocytosis was prevented by using a monolayer of antibody-coated HRBC targets, CGD monocytes, neutrophils, and lymphocytes exhibited normal ADCC activity. Similarly, antibody-coated HRBC targets in suspension could be lysed normally by CGD effector cells when phagocytosis was inhibited by the addition of in vitro colchicine. Extracellular lysis of autologous antibody-coated lymphoid cell targets in suspension was mediated normally by CGD effector cells. Thus, standard ADCC against HRBC targets in suspension is predominantly indicative of postphagocytic killing and, as such, is dependent upon a normal post-phagocytic respiratory burst of oxidative metabolism which is deficient in CGD neutrophils and monocytes. Extracellular killing of sensitized targets does not appear to be dependent upon the generation of hydrogen peroxide (H2O2) ANd/or superoxide (02-) and is normal in CGD neutrophils and monocytes. Hence, by employing CGD leukocytes as investigative probes in ADCC, fundamental mechanisms of intracellular vs. extracellular expression of cytotoxicity have been delineated.