Biomedical subjects

Z Werb

Publications and source records attributed to Z Werb.

At least 163 records · Page 9Linked to original sources

PubMed1985

Stromelysin, a connective tissue-degrading metalloendopeptidase secreted by stimulated rabbit synovial fibroblasts in parallel with collagenase. Biosynthesis, isolation, characterization, and substrates.

Rabbit synovial fibroblasts induced to undergo a specific switch in gene expression by agents that alter cell morphology secreted the neutral proteinase precursor procollagenase (apparent Mr of 53,000 and 57,000). A major Mr = 51,000 polypeptide that was always induced coordinately with procollagenase has now been identified as the proenzyme form of a metal-dependent proteinase active at neutral pH. We have named this proteinase stromelysin. Prostromelysin and procollagenase were the most prominent [35S]methionine-labeled secreted proteins of the induced fibroblasts. By the use of casein degradation as an assay for enzyme activity, stromelysin was isolated with high yield from the conditioned culture medium of 12-O-tetradecanoylphorbol 13-acetate-treated fibroblasts and migrated as an active form of Mr = 21,000 that was immunologically identical to the proteoglycan-degrading proteinase purified from rabbit bone. Immunoglobulin G from antiserum raised to purified rabbit bone proteoglycanase immunoprecipitated the Mr = 51,000 proenzyme form from conditioned medium of induced rabbit cells and also immunoprecipitated an Mr = 55,000 polypeptide from induced human fibroblasts. When rabbit prostromelysin was activated by trypsin or 4-aminophenylmercuric acetate, the proenzyme was converted to an active form of Mr = 41,000. During the course of the purification, prostromelysin was converted to an additional activatable form of Mr = 35,000 and additional active forms of Mr = 21,000-25,000, which had related peptide maps distinct from collagenase. All of these forms were immunologically cross-reactive. Purified stromelysin degraded casein, cartilage proteoglycans, fibronectin, alpha 1-proteinase inhibitor, and immunoglobulin G2a and had limited activity on laminin, elastin, type IV collagen, and gelatin, but did not degrade type I collagen. Stromelysin was inhibited by EDTA, 1,10-phenanthroline, and the specific glycoprotein tissue inhibitor of metalloproteinases isolated from human amniotic fluid and was therefore classified as a metalloproteinase.

Animals↗

PubMed1985

Tissue inhibitor of metalloproteinases. Identification of precursor forms synthesized by human fibroblasts in culture.

Precursor forms of the glycoprotein tissue inhibitor of metalloproteinases (TIMP) synthesized by human fibroblasts in culture have been identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of specific immunoprecipitates. Translation of mRNA extracted from fibroblasts in the cell-free rabbit reticulocyte lysate system yielded a single immunoprecipitable precursor of tissue inhibitor of metalloproteinases, Mr 22000. Intact fibroblasts cultured in the presence of tunicamycin synthesized an Mr 20 000 form of tissue inhibitor of metalloproteinases, detectable intracellularly and extracellularly. This is in contrast to the predominantly intracellular Mr 24 000 form synthesized during monensin treatment of cells and the normal secreted form of tissue inhibitor of metalloproteinases, Mr 29 000. Isoelectric focusing of the various immunoprecipitable precursor forms showed a progressive increase in positive charge and microheterogeneity of the protein during cellular processing. The data suggest that the inhibitor protein core, of basic pI, is glycosylated initially by the addition of mostly neutral sugars and subsequently by acidic sugars, prior to secretion.

Cells, Cultured↗

PubMed1985

Purification and characterization of an elastinolytic proteinase secreted by cercariae of Schistosoma mansoni.

An elastinolytic proteinase secreted by tissue-invasive larvae of Schistosoma mansoni has been purified to homogeneity. Size-exclusion chromatography and chromatofocusing were used to purify the enzyme 18-fold from crude larval secretions. The native enzyme has a molecular weight of 30,000, a pI of 8, a pH optimum of 9, and a calcium dependence of 2 mM. A second Mr 17,000 form of the enzyme was present in crude secretions and appears to be an autoproteolysis product. The enzyme is a serine proteinase that preferentially binds tetrapeptide inhibitors or substrates with an aromatic or hydrophobic residue at the P-1 site. In addition to being active against elastin, the enzyme degrades Azocoll, gelatin, laminin, fibronectin, keratin, and type IV collagen.

Amino Acid Sequence↗

PubMed1985

Biosynthesis of tissue inhibitor of metalloproteinases by human fibroblasts in culture. Stimulation by 12-O-tetradecanoylphorbol 13-acetate and interleukin 1 in parallel with collagenase.

Biosynthesis of the glycoprotein tissue inhibitor of metalloproteinases (TIMP) by human fibroblasts in culture has been characterized by functional assays, immunoprecipitation, and immunocytochemistry with a monospecific antiserum. As determined by radiolabeling with [35S]methionine, immunoprecipitation, and analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the secreted form of TIMP had an Mr of 29,000, whereas the form associated with the cell layer had an Mr of 24,000. Unstimulated human lung fibroblasts (HFL-1) secreted TIMP at the rate of approximately 2 micrograms/10(6) cells/24 h, and normal foreskin fibroblasts (HS 27) and skin fibroblasts from a patient with Hurler's disease (GM 1391) secreted TIMP at 0.3 and 0.2 micrograms/10(6) cells/24 h, respectively. Secretion of TIMP was stimulated up to 10-fold by treating the cells with 20-100 ng/ml of 12-O-tetradecanoylphorbol 13-acetate or 10 units/ml of human interleukin 1. In the stimulated HFL-1 cells, TIMP accounted for 0.03-0.09% of the total [35S]methionine incorporated into protein, and 0.3-0.8% of the [35S]methionine in secreted protein. Although TIMP accounted for a relatively small proportion of total protein synthesis of the fibroblasts, greater than 80% of untreated and greater than 95% of stimulated fibroblasts synthesized TIMP, as determined by indirect immunofluorescence. The treatments of the human fibroblasts that increased TIMP secretion also induced synthesis and secretion of proenzyme forms of collagenase, indicating that degradative enzymes and their controlling inhibitors may be synthesized in parallel under certain conditions.

Animals↗

PubMed1985

Factor B, the complement alternative pathway serine proteinase, is a major constitutive protein synthesized and secreted by resident and elicited mouse macrophages.

Factor B, the complement alternative pathway serine proteinase, a class III gene product of the major histocompatibility complex, is a major constitutive secretion product of mouse mononuclear phagocytes. This glycoprotein was synthesized and secreted by macrophages as a doublet of Mr 90,000 and 93,000 polypeptides that were immunoprecipitable with antibodies raised to human serum factor B, and that were indistinguishable from plasma factor B by immunoreactivity, peptide mapping, and molecular weight. Macrophage factor B was cleaved and activated to factor Bb- and Ba-like fragments by factor D and cobra venom factor. Some conversion of macrophage factor B to Bb-sized fragments occurred spontaneously in the conditioned culture medium after several hours. Factor B represented approximately 0.5% of newly synthesized protein and 4-6% of the secreted protein of resident peritoneal macrophages and macrophages elicited with thioglycollate broth, pyran copolymer, NaIO4, bacillus Calmette-Guerin, or Corynebacterium parvum. We detected synthesis of factor B immediately upon explanting these macrophages in culture; synthesis continued for several days in culture. The rate of secretion of factor B, as a proportion of total protein secretion in culture, remained constant with time. By radioimmunoassay, factor B antigens accumulated in the 24-h macrophage-conditioned culture medium at 2-10 nM, and was present in cell lysates at 4-8 nmol per 10(6) cells. We detected synthesis of factor B in bone marrow-derived macrophages as early as 5 d of culture. The P388D1 macrophage line synthesized factor B, but mouse L cells did not. In contrast, apolipoprotein E, another secreted protein of macrophages, was secreted by resident and thioglycollate-elicited macrophages but not by freshly harvested pyran copolymer-activated macrophages. Its synthesis was initiated at day 9 in culture of bone marrow-derived macrophages. These data support the classification of factor B as a constitutive biosynthetic and secreted protein of immature and mature macrophages in various states of activation. Production of factor B was modulated by treatment of macrophages in vivo or in culture with bacterial lipopolysaccharide endotoxin, which increased the synthesis, secretion, and accumulation of factor B up to 11-fold.

Animals↗

PubMed1985

Blockage of tropoelastin secretion by monensin represses tropoelastin synthesis at a pretranslational level in rat smooth muscle cells.

The blockage of protein secretion in the R22 cultured rat aortic smooth muscle cell strain with monensin repressed tropoelastin gene expression at the mRNA level by ca. 50-fold as measured by biosynthetic pulse-labeling, in vitro translation, and hybridization with a tropoelastin genomic DNA probe. These results suggest that tropoelastin gene expression is autoregulated, and they represent the first reported effect of monensin on gene expression.

Animals↗

PubMed1985

Regulation of alpha 1 proteinase inhibitor function by rabbit alveolar macrophages. Evidence for proteolytic rather than oxidative inactivation.

Rabbit alveolar macrophages were cultured in an environment conducive to the secretion of both reactive oxygen and proteinases, so that the relative importance of proteolytic and oxidative inactivation of alpha 1-proteinase inhibitor by alveolar macrophages could be evaluated. The inactivation of alpha 1-proteinase inhibitor was proportional to its proteolysis, and there was no detectable inactivation in the absence of proteolysis. Although the live macrophages were capable of secreting reactive oxygen, they did not inactivate alpha 1-proteinase inhibitor by oxidation. The inactivation of alpha 1-proteinase inhibitor by proteolysis was proportional to the secretion of elastinolytic activity by the alveolar macrophages. The inability of the alveolar macrophages to oxidize alpha 1-proteinase inhibitor was attributed to the methionine in the macrophages, in secreted proteins, and in the culture medium competing for oxidants. The data suggest that proteolytic inactivation of alpha 1-proteinase inhibitor may be important in vivo and that the methionine concentration in vivo may protect alpha 1-proteinase inhibitor from significant oxidative inactivation.

Animals↗

PubMed1985

Human synovial dendritic cells. Direct observation of transition to fibroblasts.

A subpopulation of human synovial cells develop a stellate morphology during in vitro culture. These cells, called stellate cells or dendritic cells, appear capable of collagenase production. In other tissues, particularly mouse spleen and human peripheral blood, cells with a similar shape express immune region associated (Ia) antigens, stimulate a primary mixed leukocyte reaction, and present antigen to lymphocytes. To characterize synovial dendritic cells, we observed changes in their morphology by time-lapse videomicroscopy. Parallel cultures of cells from the same specimens were observed periodically for HLA-DR surface antigens by immunofluorescence microscopy. During culture, synovial dendritic cells gradually lost their distinct morphologic appearance and became indistinguishable from fibroblasts. Moreover, fibroblasts occasionally assumed a dendritic morphology. When cells were examined at 24-48 h or later, we could not detect HLA-DR antigens on synovial dendritic cells, defined as cells with 4 or more stellate, branching projections. Cells with only 1-3 projections often had HLA-DR antigens. Because human synovial dendritic cells may lose their characteristic morphology upon culture and because they appear to lack Ia antigens in the unstimulated state, we suggest that synovial dendritic cells may be closely related to fibroblasts.

Arthritis↗

PubMed1984

Regulation of elastase and plasminogen activator secretion in resident and inflammatory macrophages by receptors for the Fc domain of immunoglobulin G.

We have determined that the interaction of IgG-coated erythrocytes (EIgG) and complement-coated erythrocytes (EIgMC) with macrophage Fc and complement receptors, respectively, modulates the secretion of the neutral proteinases, elastase, and plasminogen activator. EIgG binding and ingestion stimulated secretion of elastase and plasminogen activator less than or equal to 6-fold and 20-fold, respectively, over the 3 d following treatment. Stimulation was dependent on the IgG titer bound to each erythrocyte and was detectable at greater than 6.2 X 10(3) molecules IgG/ erythrocyte (total 0.99 nM IgG in the culture). Cytochalasin B did not inhibit stimulation, indicating that the ingestion of ligands was not necessary. Binding of EIgG to the three subclass-specific Fc receptors (IgG2a, IgG2b/IgG1, IgG3) was effective. Stimulation of elastase secretion required continued exposure of ligands to cells for up to 24 h, whereas production of plasminogen activator, which has plasma membrane-bound forms as well as secreted forms, was stimulated by exposure for 2 h. The stimulated production of elastase and plasminogen activator by triggering Fc receptors was seen only when the initial secretion rates were low. Periodate- or thioglycollate-elicited macrophages, which have high rates of proteinase secretion, were not stimulated further. EIgMC, which are bound but not ingested by resident macrophages, stimulated elastase secretion transiently, and the rate of secretion returned to the control level by 24 h. Therefore, the mode of stimulation of neutral proteinase secretion by complement receptor differed from that of Fc receptor; stimulation by complement receptor possibly involves a limited release of enzyme from intracellular stores, rather than stimulating accelerated synthesis of enzyme. Erythrocytes coated with both complement and IgG showed both the transient increase in elastase typical of complement-mediated secretion and the sustained increase typical of Fc receptor-mediated secretion. These results suggest that macrophage Fc and complement receptors regulate secretion of proteinases by receptor-specific mechanisms.

Animals↗

PubMed1984

Modulation of apoprotein E secretion in response to receptor-mediated endocytosis in resident and inflammatory macrophages.

We have determined the effect of various endocytic ligands on the secretion of ApoE by macrophages. ApoE was a major secreted protein of resident macrophages, but BCG-activated macrophages secreted little ApoE and periodate-elicited macrophages secreted intermediate amounts of ApoE. Resident, periodate-elicited, and BCG-activated mouse peritoneal macrophages were incubated with AcLDL, EIgG, EIgMC, dextran sulfate, latex, or zymosan, and the resulting protein secretion patterns were analyzed by [35S]methionine labeling and SDS-polyacrylamide gel electrophoresis. AcLDL increased total [35S]methionine incorporation into secreted proteins. Although AcLDL increased the secretion of ApoE by resident macrophages less than or equal to fivefold in a dose-dependent manner, with maximal stimulation at 4.8 micrograms/ml, it decreased the secretion of ApoE by periodate-elicited macrophages to almost nothing and did not affect the low rate of secretion of ApoE by BCG-activated macrophages. However, EIgG, which increases cellular cholesterol content of macrophages as AcLDL does, did not increase ApoE secretion, and dextran sulfate, which is recognized by the same receptor as AcLDL, also did not increase ApoE secretion. The binding and uptake of EIgG, dextran sulfate, zymosan, latex, and EIgMC all decreased the secretion of ApoE. These endocytic ligands also altered the pattern of secreted and cellular proteins other than ApoE. The pattern of response was ligand-specific. However, increased secretion of polypeptides of Mr 62,000 and 68,000 was common to many stimuli. We conclude that receptor-mediated endocytosis modulates the secretion of ApoE and other proteins pleiotypically in resident, inflammatory, and activated macrophages.

Animals↗

PubMed1984

Redistribution of ecto-5'-nucleotidase during phagocytosis by guinea pig polymorphonuclear leukocytes.

We demonstrate that 5'-nucleotidase (5'NT), an ectoenzyme of guinea pig polymorphonuclear leukocytes, is largely excluded from phagosomal membrane, rather than internalized randomly during phagocytosis of heat-killed bacteria, latex microbeads, or zymosan particles. Cells were fixed in 0.25% glutaraldehyde (pH 6.3) at 4 degrees C for 10 min and incubated in a cytochemical medium for the demonstration of 5'NT. In the nonphagocytosing cells, 5'NT was evenly distributed on the external side of the plasma membrane. In cells phagocytosing bacteria, 5'NT appeared to be cleared from the nascent phagosomal membrane; after 5 min of phagocytosis, most of the phagocytic vacuoles containing bacteria, latex, or zymosan particles were devoid of reaction product. When phagosomes containing latex particles were isolated and biochemically assayed, they contained less than 3% of the total cellular 5'NT activity even after 60 min of phagocytosis, and at that time the total cellular 5'NT activity had not declined. When the diazonium salt of sulfanilic acid (DASA), a nonpermeable ectoenzyme inhibitor, was used to determine the distribution of extracellular and intracellular 5'NT activity, no increase in DASA-insensitive intracellular 5'NT was found after phagocytosis of latex or opsonized zymosan. Cytochemical and biochemical evidence led us to conclude that 5'NT is excluded from phagosomal membrane, and that the exclusion is due to redistribution rather than to inactivation by granule enzymes.

5'-Nucleotidase↗

PubMed1984

Collagenase is a major gene product of induced rabbit synovial fibroblasts.

We have investigated the effects of the tumor-promoting phorbol diester, 12-O-tetradecanoylphorbol-13-acetate (TPA), on rabbit synovial fibroblasts, and found that this agent induced a major switch in gene expression in these cells that was marked by the specific induction of the neutral proteinase, collagenase, and was always accompanied by alterations in cell morphology. Procollagenase synthesis and secretion was first observed 6-12 h after the addition of TPA. The rate of collagenase production (1-5 U, or approximately 0.2-1 micrograms secreted procollagenase protein per 10(5) cells per 24 h) depended on the TPA concentration (1-400 ng/ml) and time of exposure (1-72 h). Procollagenase was the most prominent protein visible by direct silver staining or by autoradiography after SDS PAGE of [35S]methionine-labeled proteins. The two procollagenase bands of Mr 53,000 and 57,000, which migrated as a family of spots on two-dimensional gels and were immunoprecipitated by antibodies to purified rabbit collagenase, accounted for 23% of the newly synthesized, secreted protein in TPA-treated cells. Cell-free translation of mRNA from TPA-treated cells in rabbit reticulocyte lysate produced a single band of immunoprecipitable preprocollagenase (Mr 55,000) as a major product (5% of total) that migrated as a single spot on two-dimensional gels. Secreted procollagenase, preprocollagenase , and active collagenase (purified to homogeneity; specific activity 1.2 X 10(4) U/mg protein) had related peptide maps. Two other major secreted proteins, a neutral metalloproteinase of Mr 51,000 and a polypeptide of Mr 47,000, were also induced by TPA. In contrast to the induction of these four polypeptides, TPA decreased synthesis and secretion of a number of proteins, including collagen and fibronectin. Thus, collagenase is a convenient marker for major alterations in the pattern of protein synthesis and secretion by rabbit synovial fibroblasts treated with TPA.

Animals↗

PubMed1984

Changes in cell shape correlate with collagenase gene expression in rabbit synovial fibroblasts.

Induction of the neutral proteinase, collagenase, is a marker for a specific switch in gene expression observed in rabbit synovial fibroblasts. A variety of agents, including 12-O-tetradecanoylphorbol-13-acetate, cytochalasins B and D, trypsin, chymotrypsin, poly(2-hydroxyethylmethacrylate), and trifluoperazine induced this change in gene expression. Induction of collagenase by these agents was always correlated with a marked alteration in cell morphology, although the cells remained adherent to the culture dishes. The amount of collagenase induced was positively correlated with the degree of shape change produced by a given concentration and, to some extent, with the duration of treatment. Altered cell morphology was required only during the first few hours of treatment with inducing agents; after this time collagenase synthesis continued for up to 6 d even when agents were removed and normal flattened cell morphology was regained. All agents that altered cell morphology also produced a characteristic switch in protein secretion phenotype, characterized by the induction of procollagenase (Mr 53,000 and 57,000) and a neutral metalloproteinase (Mr 51,000), which accounted for approximately 25% and 15% of the protein secreted, respectively. Secretion of another neutral proteinase, plasminogen activator, did not correlate with increased collagenase secretion. In contrast, synthesis and secretion of a number of other polypeptides, including the extracellular matrix proteins, collagen and fibronectin, were concomitantly decreased. That changes in cell shape correlated with a program of gene expression manifested by both degradation and synthesis of extracellular macromolecules may have broad implications in development, repair, and pathologic conditions.

Animals↗

PubMed1984

Secretory products of macrophages and their physiological functions.

Macrophages secrete a variety of biologically active substances into their local milieu, including proteins, lipids, nucleotide metabolites, and oxygen metabolites. To date, more than 50 substances secreted by macrophages have been reported: enzymes; enzyme inhibitors; plasma proteins such as complement components, coagulation factors, and apolipoprotein E; factors that regulate the functions of other cells such as interferon, interleukin 1, mitogens, and angiogenesis factor; and low molecular weight substances such as reactive metabolites of oxygen and derivatives of arachidonic acids. Macrophage-derived products are probably important in the local environment, and they are believed to be important in the physiological and pathological functions of macrophages in inflammation, tissue repair, lipoprotein metabolism, acute phase response, and in microbicidal, antiviral, tumoricidal, and immunoregulatory activities; however, macrophages may not be the sole source for the secretion of some of these products. The secretion of these products is intricately regulated, developmentally and environmentally.

Animals↗

PubMed1983

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.

Animals↗

PubMed1983

Oxygen tension regulates the expression of angiogenesis factor by macrophages.

When cultured in a hypoxic environment similar to that found in the center of a wound, macrophages secreted active angiogenesis factor into the medium. Under conditions similar to those of well-oxygenated tissue, macrophages did not secrete active angiogenesis factor. Macrophages that secreted the factor at hypoxic conditions stopped secreting it when returned to room air. Thus the control of angiogenesis in wound healing may be the result of macrophages responding to tissue oxygen tension without the necessity of interacting with other cell types or biochemical signals.

Angiogenesis Inducing Agents↗

PubMed1983

Endotoxin suppresses expression of apoprotein E by mouse macrophages in vivo and in culture. A biochemical and genetic study.

We have observed that the synthesis and secretion of apo-E, a component of plasma lipoproteins, are suppressed in mouse macrophages exposed to bacterial lipopolysaccharide endotoxin (LPS) in culture or in vivo. Control mouse macrophages contained intracellular immunofluorescent apo-E, and apo-E represented about 10% of secreted protein. After intraperitoneal injection of LPS, freshly lavaged macrophages neither contained intracellular apo-E nor secreted apo-E. The suppressive effects of LPS on apo-E synthesis in culture were selective, and secretion of many other major macrophage proteins was not affected. When the LPS-elicited macrophages were cultured for 24-72 h in the absence of LPS, synthesis of apo-E was initiated. Treatment of bone marrow-derived or peritoneal macrophages in culture with less than 1 ng of LPS/ml inhibited apo-E synthesis and secretion by 18 h of treatment. Although LPS stimulates prostaglandin E2 synthesis, prostaglandin E2 itself did not suppress apo-E synthesis. Macrophages from C3H/HeJ (Lpsd/Lpsd) mice, which are resistant to LPS, were neither primed for H2O2 production nor suppressed for apo-E synthesis in response to LPS in vivo (30 micrograms/mouse) or in culture (1 microgram/ml), whereas macrophages from the co-isogenic C3H/HeN (Lpsn/Lpsn) strain were induced for H2O2 secretion and had suppressed synthesis of apo-E. Because apo-E serves as a recognition determinant for the receptor-mediated clearance of lipoproteins, the decreased synthesis of apo-E after LPS treatment may in part explain the hyperlipoproteinemia associated with endotoxins in vivo.

Animals↗

PubMed1983

Selective proteolysis of immunoglobulins by mouse macrophage elastase.

Mouse macrophage elastase, a metalloproteinase secreted by inflammatory macrophages, catalyzed the limited proteolysis of selected subclasses of mouse immunoglobulins, including monomeric IgG2a, IgG3, and some forms of IgG2b. Mouse IgG1 was resistant to elastase degradation; however, human IgG1 was degraded. IgG3 in immune complexes was cleaved in a manner similar to that of monomeric IgG3. Degradation by macrophage elastase was limited to the heavy chain, resulting in products that did not compete for binding to the macrophage Fc receptor. Macrophage elastase usually produced a pepsin-like rather than a papain-like pattern of proteolysis, resulting in the release of F(ab')2 and Fc' subfragments. This degradation of IgG differed from the papain-like cleavage of IgG by granulocyte elastase. Macrophage elastase degraded papain-generated Fc fragments of IgG2a into multiple fragments. Therefore, macrophage elastase at concentrations found in culture medium has the potential to regulate some aspects of cellular events associated with immunoglobulins.

Animals↗