Search PubMed⌕ Search

Biomedical subjects

D S Finbloom

Publications and source records attributed to D S Finbloom.

At least 73 records · Page 4Linked to original sources
PubMed1989

Intravenous immune globulin impairs anti-bacterial defences of a cyclophosphamide-treated host.

Since intravenous immune globulin (i.v.IG) could impair the clearance of autologous IgG-coated erythrocytes by the reticuloendothelial system (RES), we speculated that a patient with leucopenia who died of candida septicaemia following high dose i.v.IG may have had an impairment of his RES function. We therefore studied the ability of intact i.v.IG to impair the clearance of both soluble immune complexes and a relatively avirulent strain of E. coli from the blood of mice made leucopenic with cyclophosphamide. In the presence of leucopenia, 800 micrograms/g i.v.IG prolonged the time to clear 50% of the administered IgG anti-dinitrophenyl immune complex (T1/2) from 2.7 min to 12 min, impaired the clearance of E. coli and lowered the LD50 of the strain five-fold. This impaired clearance of soluble complexes and increased mortality (8/67 versus 37/69, P less than 0.001) following bacterial challenge was present for up to 120 and 60 min, respectively, following the administration of i.v.IG. In contrast, no significant impairment in RES function was noted when 200 micrograms/g i.v.IG was administered to leucopenic mice, or when cyclophosphamide alone was given to mice before challenge with either soluble complexes or bacteria. In addition, no change in LD50 was found when mice were pretreated with 800 micrograms/g i.v.IG alone. These data suggest that high doses of i.v.IG may impair anti-microbial defences of a leucopenic host and thereby convert a relatively avirulent organism into a pathogen.

Animals↗
PubMed1988

Internalization and degradation of human recombinant interferon-gamma in the human histiocytic lymphoma cell line, U937: relationship to Fc receptor enhancement and antiproliferation.

This report describes the association between the intracellular fate of human recombinant interferon-gamma (rIFN-gamma) and the induction of enhanced numbers of Fc receptors and an antiproliferative effect in the human monocyte-like cell line, U937. Full receptor occupancy of Bolton-Hunter labeled 125I-rIFN-gamma occurred within 10 min at 37 degrees C. However, only 50% of those molecules bound were internalized within 30 min. Residency of rIFN-gamma within the cell was 60-120 min. Eventually, 60-70% of those molecules initially bound to the cell were completely degraded within monensin-sensitive compartments of the cell as measured by the presence of trichloroacetic acid-soluble radioactivity in the medium. Exposure of rIFN-gamma to cell extracts resulted in a shift in its pI from 8 to 6, presumably due to proteolytic cleavage of carboxy-terminal basic amino acids. A single brief exposure (5-15 min) of U937 cells to rIFN-gamma resulted in enhanced numbers of receptors for the Fc portion of 125I-IgG1 as measured 24 hr later. Eighty percent of a maximal Fc receptor response occurred at only 30% receptor occupancy (50 U/ml). In contrast, repeated daily exposure of U937 cells to moderate concentrations of rIFN-gamma (125-250 U/ml) was necessary to induce an antiproliferative effect. These data suggest that a given response of the cell to rIFN-gamma may require different intensities of the signal. This may reflect the overall complexity of the response generated.

Cell Line↗
PubMed1988

Dimers of human immunoglobulin G1 provide an insufficient signal for their degradation by human monocytes.

In order to better define the processing of small soluble immune complexes by normal human monocytes, we have characterized the binding and degradation of human IgG1 monomers and covalently crosslinked dimers and heavier oligomers (composed predominantly of trimers, tetramers, and pentamers) by these cells. Whereas 15,000 molecules of monomeric IgG1 bound, about 110,000 and 65,000 IgG1 protomers of the oligomers and dimers, respectively, bound to the monocytes. Dimers bound dimerically to the cells as demonstrated by their enhanced rate of dissociation in the presence of excess heat-aggregated gamma-globulin. Despite occupying two Fc receptors, the intracellular fate of dimers was essentially that of the monomers; only 5-10% of the bound protomers were degraded. In contrast, approximately 40,000 IgG protomers of the heavy oligomers (30% of total bound) were degraded over a 5-hr incubation period. Since binding of a heavier complex, is required for degradation by the monocyte, dimeric immune complexes can generally escape the normal clearance mechanisms of the host.

Antigen-Antibody Complex↗
PubMed1987

B cell stimulatory factor-1 (interleukin 4) activates macrophages for increased tumoricidal activity and expression of Ia antigens.

Macrophages are activated by lymphokines (LK) to kill tumor cell and microbial targets. Interferon-gamma (IFN) is the major LK activity in conventional, antigen or mitogen-stimulated spleen cell culture fluids for induction of these macrophage effector functions. In view of the recent demonstration that murine macrophage-like cell lines have receptors for B cell stimulatory factor-1/interleukin 4 (BSF-1), a possible role for BSF-1 in regulation of macrophage function was considered. In this communication, thioglycollate-elicited murine peritoneal macrophages were shown to express about 2300 high affinity (Ka approximately 2 X 10(10) M-1) BSF-1 receptors/cell. Peritoneal macrophages treated with purified, T cell-derived BSF-1 developed potent tumoricidal activity against fibrosarcoma target cells. The concentration of BSF-1 that induced 50% of maximal tumor cytotoxicity was 38 +/- 4 U/ml for seven experiments; similar dose-responses were observed with recombinant BSF-1. That BSF-1 dose-responses for induction of macrophage-mediated tumor cytotoxicity were not affected by 5 micrograms/ml polymyxin B suggested that contaminant endotoxins played little or no role in cytotoxic activity. BSF-1 alone (less than or equal to 500 U/ml) was not directly toxic to tumor cells or macrophages. Macrophage tumoricidal activity induced by BSF-1 but not by IFN was inhibited greater than or equal to 90% with monoclonal anti-BSF-1 antibody. BSF-1 induced Ia antigen expression on peritoneal macrophages and increased (twofold to threefold) FcR(II)-dependent binding of murine IgG immune complexes to bone marrow-derived macrophages (greater than 98% macrophages). Based on these findings, it was concluded that BSF-1 is a potent macrophage activation factor.

Animals↗
PubMed1987

Endocytosis of particulate and soluble IgG immune complexes: differential effects of cytoskeletal modulating agents.

We determined the ability of cytoskeletal modulating agents to affect endocytosis of particulate and soluble immune complexes. Either immunoglobulin G-opsonized 51Cr-labelled erythrocytes (E) or 125I-labelled soluble IgG anti-dinitrophenyl immune complexes (IC) were added to adherent murine peritoneal macrophages and the extent of internalization was measured. Either intracellular 51Cr radioactivity or trichloroacetic acid soluble 125I radioactivity was monitored as an indication of uptake by the cell. In addition to cytochalasin B and colchicine, the phospholipid methylation inhibitors, 3-deazaadenosine and 3-deaza(+/-)aristeromycin, were used. Whereas incubation of macrophages with colchicine alone resulted in 50% inhibition of uptake of E-IgG, there was no effect on the degradation of soluble IC. Both cytochalasin B and colchicine produced a 95% inhibition of E-IgG uptake by macrophages, but these drugs only minimally inhibited (17%) the degradation of soluble immune complexes. Both inhibitors of methylation produced a 50% decrease in phospholipid methylation in treated cells. However, only 3-deazaadenosine inhibited phagocytosis (50% of control for E-IgG and 75% of control for soluble IC). These data suggest that an intact cytoskeleton is necessary for the uptake of a particulate immune complex and much less important for the internalization and degradation of these model soluble immune complexes. In addition, inhibition of phospholipid methylation reactions alone do not impare the uptake and degradation of either a soluble or a particulate immune complex.

Adenosine↗
PubMed1986

Corticosteroids enhance the binding of recombinant interferon-gamma to cultured human monocytes.

Human peripheral blood monocytes possess receptors on their surface for human interferon-gamma (IFN-gamma). Inasmuch as the biologic effects of IFN-gamma are thought to be mediated through binding of the molecule to this receptor, modulation of receptor number may be a means for enhancing the effect of IFN-gamma. We examined this possibility by treating human monocytes in culture with dexamethasone. At a dexamethasone concentration of 200 nM, there was a twofold increase in the number of 125I-recombinant IFN-gamma molecules bound to the cell. An effect was noted at concentrations of dexamethasone greater than 50 nM, and was observed as early as after 18 hr of treatment. The observed effect was the result of both a 50% decrease in receptor number in untreated cells and an increase to pretreatment levels or greater in cells incubated with dexamethasone. These results suggest that dexamethasone may modulate the effects of IFN-gamma on monocytes by changes in receptor number.

Cells, Cultured↗
PubMed1986

A lymphokine distinct from interferon-gamma that activates human monocytes to kill Leishmania donovani in vitro.

Human interferon-gamma (IFN-gamma), a T cell lymphokine (LK), activates monocytes to kill many intra- and extracellular pathogens. In fact, previous reports assert that all activity in LK for macrophage activation is due to IFN-gamma. To test this assertion, we examined monocyte interactions with amastigotes of Leishmania donovani after treatment with recombinant DNA or affinity-purified leukocyte IFN-gamma and IFN-gamma containing LK. Cells treated with at least 200 IU/ml IFN-gamma were microbicidal for L. donovani. Analysis of IFN-gamma dose responses for induction of microbicidal activity by recombinant IFN-gamma (r-IFN-gamma) and LK, however, documented a striking difference: LK was 25-fold more efficient than r-IFN-gamma at equivalent IFN-gamma titers. This large difference suggested that monocyte activation factor(s) in LK may not be IFN-gamma. Rabbit anti-IFN-gamma completely inhibited antiviral activity in LK but did not abrogate the ability to induce monocyte cytotoxicity against leishmania. Furthermore, removal of IFN-gamma from LK by monoclonal anti-IFN-gamma affinity chromatography or by treatment with anti-IFN-gamma followed by staphylococcal protein A chromatography also did not inhibit LK activity. Fractionation of LK on Sephadex G-100 revealed two activity peaks: one in the 50,000 to 60,000 m.w. range coincident with IFN-gamma, and the other at 25,000 to 30,000 daltons with no IFN-gamma. These studies document LK physicochemically and antigenically distinct from IFN-gamma that activate monocytes to kill L. donovani. Such novel factors may have broad import for the study of macrophage-mediated host defenses and for development of immunotherapeutic regimens.

Animals↗
PubMed1986

Subcellular characterization of the endocytosis of small oligomers of mouse immunoglobulin G in murine macrophages.

To characterize the internalization and degradation of model immune complexes in murine macrophages, the endocytosis of well-defined radiolabeled IgG dimers and heavy oligomers (5 to 7 IgG molecules per complex), which were covalently cross-linked at the antigen-combining site, was studied. Of those heavy oligomers which were bound to the cell at 4 degrees C, 50 to 60% (400,000 molecules of IgG) were internalized within 30 min at 37 degrees C and, subsequently, were completely degraded over a period of 3 hr. Low pH had little effect on the dissociation of the oligomer from its receptor. The degradation of oligomers was markedly inhibited when macrophages were treated with monensin, a proton ionophore which raises organelle pH. Because this treatment did not prevent the delivery of oligomer into the lysosome, the transport of a soluble complex of IgG from the cell surface to the lysosome was not a pH-dependent event. On the other hand, 25 to 30% (50,000 molecules) of those dimers capable of binding to the cell entered the macrophage, but only 5000 molecules were degraded. When macrophages were studied by using density gradient centrifugation, within 15 min, heavy oligomers were found in a vesicle which sedimented at a density between that of the plasma membrane and lysosome. The density of this vesicle was similar to that of endosomes studied in other receptor-ligand systems. Heavy oligomers were within lysosomes shortly thereafter. Incubation of cells at 18 degrees C prevented the appearance of heavy oligomer within the lysosomes and resulted in the concentration of oligomers within an intracellular compartment of a density slightly heavier than that of plasma membrane. At 37 degrees C, dimers sedimented in a similar region of the gradient. But unlike heavy oligomers, dimers never entered lysosomes. These data suggest that the degree of Fc receptor clustering induced by oligomers of IgG influenced the intracellular fate of the ligand.

Animals↗
PubMed1985

Binding, endocytosis, and degradation of model immune complexes by murine macrophages at various levels of activation.

To determine if stimulation of macrophages enhances their capacity to recognize and process immune complexes, the binding, endocytosis, and degradation of soluble model immune complexes in murine macrophages have been measured. These complexes are composed of covalently crosslinked dimers and heavy oligomers of murine IgG antidinitrophenyl antibodies. Resident (unstimulated), inflammatory (thioglycolate-elicited), and activated (bacillus Calmette-Guerin-elicited) macrophages were studied. Cells elicited with either agent bound five times more dimers or heavy oligomers than did resident cells. Stimulated macrophages internalized and then degraded 50-60% of those heavy oligomers initially bound to the surface of the cell. Resident macrophages, however, were about 70% as efficient as stimulated cells at degrading intracellular complexes. Although dimers avidly bound to all three types of macrophages, they were internalized poorly and were degraded minimally. Intracellular complexes were degraded within lysosomes as determined by centrifugation of cell homogenates on Percoll gradients. Following endocytosis of heavy oligomers, Fc receptors on each type of macrophage were down-modulated to 30% of control levels.

Animals↗
PubMed1985

The characteristics of binding of human recombinant interferon-gamma to its receptor on human monocytes and human monocyte-like cell lines.

Interferon-gamma (IFN-gamma) induces many effector functions in macrophages, presumably through binding to cell surface receptors. Such receptors have been documented in murine macrophages. This report demonstrates that IFN-gamma interacts with a specific receptor on human monocytes and monocyte-like cell lines, U937 and HL60. Recombinant IFN-gamma (rIFN-gamma) was radioiodinated by using Bolton-Hunter reagent to high specific activity. 125I-rIFN-gamma bound in a specific and saturable manner. Saturation of binding sites occurred at 10(-9) M (300 U/ml); there were 4000 specific binding sites per cell for both monocytes and the cell lines. Purified lymphocyte-derived IFN-gamma as well as rIFN-gamma competed for binding sites with 125I-rIFN-gamma. There was no inhibition of binding of the 125I-rIFN-gamma by rIFN-alpha or rIFN-beta. The forward rate constant, k1, at 4 degrees C was about 8 X 10(5) M-1 sec-1 for each cell type studied. In the presence of excess ligand, the dissociation rate constant, k-1, was about 2 X 10(-4) sec-1. The Ka calculated from these constants (4 X 10(9) M-1) agreed closely with that calculated from experiments performed at equilibrium (8 X 10(9) M-1). Because the dissociation of rIFN-gamma from cells was enhanced in the presence of ligand, interactions between binding sites of a negative cooperative type could be operative. These studies demonstrate that rIFN-gamma binds in a specific and saturable manner and with high affinity to a receptor on human monocytes as well as monocyte-like cell lines.

Binding Sites↗
PubMed1985

Comparison of hydroxychloroquine and chloroquine use and the development of retinal toxicity.

We assessed the frequency of retinal toxicity in patients receiving either chloroquine or hydroxychloroquine and factors which may predict patient susceptibility to toxicity. The overall frequency of retinopathy was 6% (7 of 110 patients). Of the 31 patients receiving chloroquine alone, 6 developed toxicity (19%). In contrast, of the 66 patients receiving hydroxychloroquine, none developed retinopathy. Retinopathy was associated with greater age and with greater accumulative doses of chloroquine. Thus, hydroxychloroquine can be used safely with minimal risk of toxicity.

Adult↗
PubMed1983

Interferon-induced enhancement of macrophage Fc receptor expression: beta-interferon treatment of C3H/HeJ macrophages results in increased numbers and density of Fc receptors.

Previous studies demonstrated that the augmentation of Fc receptor-(FcR) mediated phagocytosis and binding of opsonized sheep erythrocytes is cytokine mediated. Specifically, beta-interferon- (beta-IFN) and gamma-IFN-rich preparations were shown to increase binding and phagocytosis of opsonized erythrocytes by C3H/HeJ macrophages. In this report we extend these studies by examination of the mechanisms by which highly purified beta-IFN increases FcR capacity in C3H/HeJ macrophages. Our findings indicate that beta-IFN augments FcR function for both IgG2a and IgG2b receptor subclasses. Moreover, this increased ability to bind and phagocytose opsonized erythrocytes is associated with a concomitant increase in both the number and surface membrane density of FcR.

Animals↗
PubMed1983

Isolation of cross-linked IgE-receptor complexes from rat macrophages.

Receptors for IgE on macrophages have been characterized by binding assays (1-3), but to date there has been only one report on the isolation of this receptor from macrophages, with use of the cell line U937 (4). In that report the receptor was isolated by using a heavily absorbed polyclonal antibody raised against lymphocytes bearing receptors for IgE (5). Monomeric IgE binds so weakly to macrophages that affinity chromatography of IgE-receptor complexes, such as has been used for isolation of the receptors for IgE on basophils (6) and for IgG on macrophages (7), cannot be readily accomplished. We have used oligomers of IgE to enhance the binding of IgE to macrophages (3), but this alone would not be sufficient because--depending on whether the receptors are multi- or univalent--once the cells are solubilized, multipoint attachment would again be reduced if not abrogated. In this report we describe the use of cross-linking reagents to stabilize further the interaction between IgE and its receptor on peritoneal macrophages. With this approach we have found that the receptor is likely to be composed of two chains whose gross properties are similar to the polypeptides constituting the receptor with high affinity for monomeric IgE on rat basophilic leukemia cells and mast cells.

Animals↗
PubMed1983

Abnormal binding of soluble IgG immune complexes to hepatic nonparenchymal cells of autoimmune mice.

Because the liver is the major organ responsible for removal of soluble immune complexes (IC), the surface binding characteristics of preformed model IC to unstimulated mouse liver nonparenchymal cells (NPC) in suspension were studied. NPC of non-autoimmune C3H/FeJ, C3H/HeJ, A/J, DBA/2 and the autoimmune NZB/W F1 and MRL/lpr female mice of various ages were isolated by perfusion of the portal vein with collagenase followed by separation of NPC from hepatocytes with a metrizamide gradient. Thirty-five percent of NPC of all mouse strains were nonspecific esterase-positive and phagocytosed latex beads. Radiolabeled mouse IgG anti-DNP covalently cross-linked stable IC were separated by gel filtration and bound to NPC under various conditions. Marked differences were noted in maximal number of IC bound per cell between the autoimmune and non-autoimmune mouse strains: 3.3 to 4.0 X 10(5) in the non-autoimmune strains vs 0.3 to 1.4 X 10(5) molecules of IC bound per cell in the autoimmune strains at 1 to 6 mo. Insignificant differences were noted in Ka by Scatchard plot analysis (3.5 to 5.0 X 10(8) M-1) and rate of reversibility of binding as determined by dissociation of surface-bound IC with an excess of heat-aggregated gamma-globulin (T 1/2:1.5 to 2 min). These data demonstrate a decreased number of available binding sites for IC in unstimulated NPC from NZB/W F1 and MRL/lpr female mice throughout their life spans. Although the findings are consistent with saturation of binding sites of the NPC with native IC, the abnormality found in the 1-mo-old autoimmune mice (who do not have detectable autoantibodies) suggests a primary defect in FC receptor expression or an altered state of activation of NPC that may contribute to the disease process.

Animals↗
PubMed1982

Binding of immunoglobulin E to the receptor on rat peritoneal macrophages.

The binding of radiolabeled monomers and chemically cross-linked dimers of rat immunoglobulin E (IgE) to peritoneal macrophages of rats was characterized. With either form, 40,000 to 50,000 molecules of IgE were specifically bound per cell under conditions where no endocytosis occurred. Monomeric IgE dissociated from macrophages within minutes, whereas dimers of IgE had a much slower rate of dissociation. Denatured rat IgE or native human IgE failed to inhibit the binding, but mouse IgE and, to a limited extent, rat IgG did. Oligomers of IgE by virtue of their tighter association with the receptor should prove useful in isolation of the receptor.

Animals↗