Effects of mononuclear phagocyte system modulating agents on Fc and C3 receptors of adherent cells

Agents which modulate the mononuclear phagocyte system (MPS) were examined for their effects on Fc and C3 receptors of adherent cells (A-cells) as judged by rosette formation. Dextran sulphate, carrageenan, and immune complexes, known as MPS suppressants, reduced the percentage of receptor-positive A-cells, while levamisole, known as a MPS-activator, increased the percentage in vitro. The changes in the percentage of Fc receptor were parallel to those of the C3 receptor in vitro. The effects of these agents were also examined in vivo.     

In-vitro modification of membrane receptors on cells of the mononuclear phagocyte system.

EA and EAC receptors have been studied on non-elicited and paraffin-induced macrophages, under a variety of culture conditions in vitro, for up to 7 days. A large decrease in the number of macrophages showing EAC receptors was found after treatment of the cells with BCG, but not "inert" particles such as latex and zymosan. This was reversible by 7 days. In the presence of a toxic material, Al(OH)3, both EA and EAC receptors were partially lost. The results obtained have been related to previous results obtained with cryostat sections of human leprosy skin lesions.     

The heterogeneity of Fc receptors on human peripheral mononuclear blood cells.

Fc-receptor positive peripheral blood mononuclear cells (PMBC) behaved differently after a temperature shift from 4 to 37 degrees. Two types could be distinguished. Type I FcRI+PMBC were transformed to FcR-while type II FcRII+PMBC retained their FcR as measured by EA rosettes. The supernatants of the PMBC or the shed receptor purified on a Sepharose 4B-aggregated human IgG column blocked the EAR formation of FcRI+PMBC but had no effect on EAR information of FcRII+PMBC. An investigation was made into the reason why rosette formation by Fcrii+ cells could not be inhibited by FcRI. As an explanation, the role of differences in affinity or subclass specificity was excluded while the binding site(s) on the IgG molecule for FcRI and II proved to be different. The FcRII+PMBC had a greater cellular avidity for sensitized erythrocytes than FcRI+PMBC. The different states of FcR-s in the cell membrane are discussed as a possible source of heterogeneity.     

Relationship of mouse erythrocyte binding receptor on peripheral blood mononuclear cells to receptors for IgG Fc and C3

When peripheral blood mononuclear cells separated at 4 degrees C were incubated at 37 degrees C, they shed their surface receptors. Total absorption of the released mouse erythrocyte binding receptors from the supernatant of the cell suspension with mouse erythrocytes did not lead to a change in the IgG Fc and C3 receptor content of the supernatant. On removal of the C3 or IgG Fc receptors, the quantity of mouse erythrocyte binding receptor remained unchanged. These observations indicate that the three receptors are mutually independent structures, or undergo dissociation in the course of the shedding.     

Preformed postribosomal pool of Fc receptors on human peripheral mononuclear blood cells

The shedding of surface structures due to a 4°C to 37°C temperature shift is followed by a regeneration within 4 h. To demonstrate the shedding and reappearance of Fc receptors, the method of anti-D EA rosettes was used. Three subsequent temperature shifts were followed by repeated reappearance of FcR in 76% of the cases investigated. In several cases, however, besides the shedding of FcR into the medium, the percentage of Ea rosette-forming cells did not decrease, which points to the possibility that repeated temperature shifts may cause shedding and expression of FcR at the same time. In 24% of the cases we could not observe repeated reappearances, possibly due to the exhaustion of an FcR reservoir.Inhibition of protein synthesis with cycloheximide, suppression of cell metabolism by adjustment to low temperatures and addition of sodium azide did not influence the reappearance of FcR following the temperature shift.These findings suggest that the reappearance of FcR after temperature shift is the consequence of a membrane rearrangement in which preformed FcR become expressed on the cell surface.     

The identification of Fc and C3 receptors on human neutrophils.

Electroimmunoassay is a simple, rapid and accurate method for quantitating the serum proteins. By use of glutaraldehyde, intermolecular cross-linkage of immunoglobulins to albumin was effected. The conjugation resulted in increased electrophoretic mobility of the immunoglobulins without perceptible change in antigenic determinants. With a Tris-EDTA-boric acid buffer system, the cross-linked immunoglobulins migrated anodically in an electrical field.Six serum proteins from each of 20 samples were quantitated by electroimmunoassay, and the results correlated with values obtained by radial immunodiffusion.     

Subplasmalemmal linear densities in cells of the mononuclear phagocyte system in lung.

The presence of subplasmalemmal linear densities in cells of the mononuclear phagocyte system was investigated in pulmonary biopsies from 33 patients with fibrotic lung disorders. Subplasmalemmal linear densities, consisting of a thin layer of electron-dense material immediately subjacent to the inner leaflet of the plasma membrane, were found in 30 of the 33 patients, including each of 6 patients with pulmonary sarcoidosis, 18 of 19 patients with idiopathic pulmonary fibrosis, 4 of 5 patients with collagen-vascular diseases, 1 patient with pulmonary lymphangioleiomyomatosis, and 1 patient with marked interstitial pulmonary fibrosis associated with squamous cell carcinoma of the lung. Subplasmalemmal linear densities were found in epithelioid cells, macrophages, and giant cells in granulomas in the 6 patients with sarcoidosis and in alveolar macrophages in 4 of these patients. In patients with other fibrotic lung disorders, subplasmalemmal linear densities were limited in distribution to interstitial and alveolar macrophages. In all patients with sarcoidosis some of the subplasmalemmal linear densities of adjacent mononuclear phagocytes, particularly of those in granulomas, were paired and formed specialized intercellular junctions. Such junctions also were observed in macrophages in 10 of the patients with other fibrotic lung disorders. The junctions formed by subplasmalemmal linear densities differed from other types of junctional structures. Subplasmalemmal linear densities appear to function in 1) the binding of action filalar junctions, which may contribute to the immobilization of mononuclear phagocytes in granulomas and alveolar lumens.     

Interaction between actomyosin complexes and Fc receptors on human peripheral mononuclear blood cells

The soluble FcRI shed from HPMBC following 4–37°C temperature shift interacts with AM, A-HMM and A-S1, respectively, but do not bind to A, M, HMM or S1. In contrast to the monovalent soluble FcRI the multivalent A-HMM-FcRI and A-S1-FcRI complexes agglutinate EA cells. Due to the interaction of soluble FcR with muscle proteins an alteration in the binding properties of the receptor was observed. FcRI in soluble form inhibits only the EA rosette formation of FcRI⁺ HPMBC in contrast to FcRI-A-HMM and FcRI-A-S1 complexes inhibiting the rosette formation of FcRI⁺ and FcRII⁺ cells as well. Based on these observations one can suppose that depending on their anchoring to cytoskeletal structures the FcRs possess one or two binding sites.     

Evaluation of aggregated IgG in mice as an Fc receptor specific probe of the hepatic mononuclear phagocyte system.

In experimental models of immune complex diseases the hepatic mononuclear phagocyte system removes circulating immune complexes (CIC) by interaction with Fc receptors, and the spleen has a relatively insignificant role in this function. We have used heat-aggregated human IgG (AHGG) to detect altered hepatic mononuclear phagocyte system activity in an acute immune complex model in mice in order to evaluate its suitability for possible use in humans. Immune complexes inhibited the clearance of AHGG, as a function of the dose and of the time after injection of complexes. The delayed clearance resulted from decreased hepatic uptake of the AHGG. Alterations in the comparatively small splenic uptake of AHGG did not correlate with changes in the clearance or the hepatic uptake that were produced by the complexes. Studies with Rose Bengal showed that the complexes caused a small but definite decrease in hepatic blood flow. Immune complexes also inhibited the clearance and hepatic uptake of aggregated mouse albumin and aggregated ovalbumin. The aggregated albumins, however, were cleared very rapidly, indicating high extraction ratios, so their clearance was more affected by the decreased blood flow than the clearance of AHGG. We conclude that a small dose of AHGG is a sensitive probe for hepatic Fc receptor function and has potential for human use.     

Effects of cholera exotoxin on Fc receptor activity of lymphoid cells and mononuclear phagocytes.

The effect of cholera exotoxin and aminophylline on Fc receptors in a murine lymphoid-cell line and in rabbit pulmonary alveolar macrophages has been investigated. Although both agents elevated intracellular cyclic AMP levels in macrophages and lymphoid cells, the effects on Fc receptor expression were distinct. Cholera toxin at 10 microng/ml reversibly inhibited Fc-receptor activity in the murine lymphoid cell line. In contrast, cholera toxin at 10 microng/ml or 0-01 microng/ml was ineffective in altering pulmonary alveolar macrophage receptor expression. Fc receptor activity on the macrophage was reduced by 20-30 per cent following incubation with aminophylline, (10(-3)M) from 0-6 h. There was no direct correlation between Fc-receptor activity and cyclic AMP levels in the cells studied. The differential susceptibility of these lymphoid and phagocytic cell populations to cholera toxin and also toward aminophylline suggests that there may be fundamental differences in topography on the membrane surface, or in the intracellular regulation of Fc receptors between lymphoid and phagocytic cells.     

Modulation of neutrophil Fc and C3b receptors

The effect of the interaction between human neutrophils and aggregated IgG on the expression of the receptors for the Fc portion of IgG (FcR) and for the C3b (C3R) has been investigated. Incubation of neutrophils with the appropriate concentrations of aggregated IgG at 37°C caused the loss of both the FcR and the C3R. This loss (modulation) was energy dependent (i.e., did not take place in cells incubated in the cold) and irreversible in that neutrophils did not reexpress either of the two receptors even upon prolonged incubation in vitro. The mechanisms leading to the modulation of FcR and C3R were different. FcR modulation was independent of the activation of the respiratory burst, since it occurred also in neutrophils from chronic granulomatous disease patients and was not induced by treatment of normal neutrophils with drugs such as phorbol myristate acetate (PMA), known to activate the respiratory burst. The FcR modulation was rather related to the redistribution (“capping”) and endocytosis of the FcR induced by the interaction with aggregated IgG. This possibility was supported by the finding that FcR modulation was blocked by inhibitors of phagocytosis and by the observation that aggregated IgG, tagged with a fluorescent dye, were “capped” and subsequently endocytosed by metabo'lically active cells. Modulation of C3R was dependent upon the activation of the respiratory burst induced by the interaction of aggregated IgG with the neutrophils. This hypothesis was also supported by the finding that the modulation of C3R was induced by treatment of the cells with PMA and did not occur in chronic granulomatous disease neutrophils treated with aggregated IgG or PMA. Furthermore the modulation of C3R was inhibited by the addition of catalase, suggesting that such modulation was consequent to the damaging effect of the oxygen active by-products on the receptor structures. In addition to the C3R modulation described above, another type of C3R loss was observed. This occurred in chronic granulomatous disease (CGD) neutrophils following interaction with the appropriate antigen-antibodycomplement complexes. In these cells, phagocytocis of the complexes caused a concomitant modulation of the C3R that was possibly related to the redistribution and endocytosis of the C3R structures.     

Dynamics of mononuclear phagocyte system Fc receptor function in systemic lupus erythematosus. Relation to disease activity and circulating immune complexes

Seventeen pairs of longitudinal studies of mononuclear phagocyte system (MPS) Fc receptor function in 15 patients with systemic lupus were performed to explore the dynamic range of Fc receptor dysfunction in lupus and to establish the relationships between MPS function, clinical disease activity and circulating immune complexes (CIC). Fc receptor function was measured by the clearance of IgG sensitized autologous erythrocytes. At the time of first study the degree of MPS dysfunction was correlated with both clinical activity (P less than 0.05) and CIC (P less than 0.05). At follow-up patients with a change in clinical status show significantly larger changes in clearance function compared to clinically stable patients (206 min vs 7 min; P less than 0.001). MPS function changed concordantly with a change in clinical status in all cases (P = 0.002). Longitudinal assessments did not demonstrate concordance of changes in MPS function and CIC, measured by three different assays. The MPS Fc receptor defect in systemic lupus is dynamic and closely associated with disease activity. The lack of concordance of the defect with changes in CIC suggests that either CIC does not adequately reflect receptor site saturation or that other factors may also contribute to the magnitude of MPS dysfunction.     

Surface membrane determinants on childhood acute lymphocytic leukemia cells: immunoglobulin, Fc and C3 receptors.

Most reports have now described two populations of childhood ALL patients: those with thymic (T) cell receptors and those lacking receptors on their neoplastic cells. Assays for the surface receptors of the T and thymic-independent (B) system were used to study forty-seven patients with ALL whose bone marrow contained a mean of 85% leukaemic cells. Two patients had T-cell disease and thirty-six were non-T and non-B. nine patients were identified whose leukaemic cells had membrane properties associated with the B-cell system: surface immunoglobulin, Fc receptors and/or complement receptors. Combined T and B receptors were found in one case. The same surface characteristics were found on leukaemic cells from these patients' bone marrow, blood, pleural and cerebrospinal fluid. Studies showed that the leukaemic cells were not of monocytic or granulocytic origin. Although a remission was obtained in each patient, the relapse rate of the B-cell group was worse than a similarly treated group of thirty-six non-T, non-B ALL patients (P less than 0.001). Initial total leucocyte counts of the B-cell group were greater than the non-T, non-B group (P 0.05), but when the patients in both groups with total leucocyte counts greater than 25,000/mm3 were compared, the relapse rate of the B-cell patients was significantly worse (P less than 0.025). The results show that patients with leukaemic cells possessing B-cell properties comprise a significant proportion of ALL cases, and their presence on leukaemic cells has an ominous significance.     

单核吞噬细胞和血浆纤维结合蛋白在大鼠多器官衰竭中的作用

本研究通过持续低血流灌注造成大鼠多器管衰竭模型，观察ＭＯＦ时大鼠肝、肾、肺等器官的功能改变，腹腔巨噬细胞吞噬率、吞噬指数的改变及血浆纤维结合蛋白的改变，旨在探讨大鼠ＭＯＦ时单核吞噬细胞和血浆Ｆｎ的变化作用。实验结果表明，腹腔巨噬细胞吞噬率，吞噬指数和血浆Ｆｎ的变化和作用。实验结果表明，腹腔巨噬细胞吞噬率、吞噬指数和血浆Ｆｎ在ＭＯＦ时显著降低（Ｐ＜０．０１），且与ＭＯＦ的程度相平行。提示单核吞噬细胞     

The effect of complement in adherent immune complexes on Fc and C3 receptor expression in human monocytes.

The effect of complement in surface-bound immune complexes on the expression of Fc and C3 receptors in membranes of adherent human monocytes was examined. Monocytes were isolated from mononuclear leucocyte preparations by adherence to substrates containing fibrin, fibrin with immune complexes (containing rabbit IgG antibodies), or fibrin with immune complexes and mouse complement. Fc or C3 receptors on the top or exposed surface of the monocytes were detected by rosette formation with sheep erythrocytes coated with IgG (EA) or IgM and complement (EAC). Monocytes adherent to surface-bound immune complexes exhibited an absence of EA rosette-forming ability without any change in EAC rosettes. This specific loss of Fc receptor function was induced more easily in freshly-isolated monocytes than in cells maintained in suspension culture for up to 7 days. The presence of complement in the immune complex substrates did not reverse the decrease in Fc receptors seen with freshly-isolated or cultured monocytes. Monocytes adherent to immune complexes and complement exhibited a decrease in C3 receptor function. This decrease was more readily induced in cells cultured for three days in the presence of serum than in freshly-isolated monocytes. Experiments performed with EAC or immune complex substrates relatively enriched in C3b or C3bi indicated that C3b in the substrate induced a decrease in monocyte C3b receptors and C3bi led to a decrease in C3bi receptors. No evidence was found for C3d receptors on the human monocytes although these receptors on a subpopulation of human lymphocytes appeared to be altered in a similar fashion.     

Identification of cells of the human mononuclear phagocyte system with rat monoclonal antibodies

Five rat monoclonal antibodies (McAbs) to human macrophages are described: YTH 8.18, YTH 25.7, YTH 51.1, YTH 85.12.1, and YHB 65.5. These McAbs are divided into three groups, since YTH 8.18, YTH 51.1, and YHB 65.5 are thought to identify the same antigen. These McAbs react with some bone marrow blast cells, granulocytes, and different percentages of peripheral blood monocytes. When studied on different body tissues, they were found to identify all members of the mononuclear phagocyte system (MPS), except Langerhans cells of skin and epithelium and in the case of one group (YTH 8.18/YTH 51.1/YHB 65.5) osteoclasts. In nine reactive lymph nodes the anti macrophage McAbs identified germinal centre macrophages, sinus macrophages, and interdigitating cells, but not dendritic reticulum cells. They also identified epithelioid macrophages and Langhans-type multi-nucleated giant cells in lymph nodes involved in granulomatous lesions (sarcoidosis and toxoplasmosis). In 24 cases of non-Hodgkin's lymphoma, the antimacrophage McAbs identified reactive macrophages in cases of B- or T-lymphocyte origin, whereas in three selected cases of true histiocytic lymphoma all the McAbs were found to be reactive with the vast majority of neoplastic macrophages as they were with the cells of a neoplastic macrophage line (U937). The possible use of these McAbs in the identification of benign and malignant macrophages in different systems is discussed.     

C3 receptors on direct plaque-forming cells.

Using a rosette technique it is shown that only a small proportion of direct plaque-forming cells posses detectable C3 receptors 5 and 7 days after antigenic stimulation. The significance of this result is discussed.     

Effect of stimulation of mononuclear phagocyte system by yeast polysaccharides on endocytosis by liver cells

Laboratory of Cellular Biochemistry and Physiology, Institute of Physiology, Siberian Branch, Russian Academy of Medical Sciences, Novosibirsk. (Presented by Academician of the Russian Academy of Medical Sciences Yu. I. Borodin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 114, No. 9, pp. 276–278, September, 1992.     

Normal human serum restores the expression of Fc gamma receptors in immune complex-blocked human mononuclear cells.

Thirty-three TO mice, 24 of which had received progesterone, were infected originally by Mycoplasma pulmonis given vaginally. Thirty-one of the mice were free of the organisms in the genital tract 236 days later at which time all of them were treated again with progesterone and rechallenged with M. pulmonis vaginally. All 31 mice were resistant. In contrast, of 21 TO mice of the same age that were not infected originally 15 (71%) became infected persistently after vaginal rechallenge. In similar experiments, 12 CBA mice, nine of which had received progesterone, were infected originally. Ten of these mice were free of the organisms genitally 2 years later, at which time all of them were rechallenged vaginally. Only two mice (20%) were reinfected, whereas six (86%) out of seven mice, not infected originally, were reinfected. Autopsy examination revealed that neither infection nor immunity was confined to the lower genital tract. Thus, M. pulmonis organisms were not detected in the upper tract of five TO mice that remained mycoplasma-free vaginally after rechallenge. The contribution of oropharyngeal M. pulmonis infection, which occurred in most of the mice, to the solid, long-lasting genital-tract resistance was difficult to assess, but in two mice, at least, immunity was not afforded by such infection.