Plasma membrane polypeptides of resident and activated mouse peritoneal macrophages

Effect of lectins on mouse peritoneal macrophage phagocytic activity

We studied the in vitro ability of lectin-treated murine peritoneal macrophages to attach and phagocytize particulate antigens. Glucose and mannose specific lectins such as Con-A and lentil lectin, as well as complex lactosamine residues specific lectins, such as Phaseolus vulgaris var. cacahuate and Phaseolus coccineus var. alubia, increased the macrophage phagocytic activity towards heterologous erythrocytes, whereas peanut agglutinin, a galactose-specific lectin, diminished the macrophage phagocytic activity. These results suggest that a galactose-N-acetyl-D galactosamine-containing structure could participate as negative modulator of the phagocytic activity.

Zanvil Alexander Cohn 1926-1993

Zanvil Alexander Cohn, an editor of this Journal since 1973, died suddenly on June 28, 1993. Cohn is best known as the father of the current era of macrophage biology. Many of his scientific accomplishments are recounted here, beginning with seminal studies on the granules of phagocytes that were performed with his close colleague and former editor of this Journal, James Hirsch. Cohn and Hirsch identified the granules as lysosomes that discharged their contents of digestive enzymes into vacuoles containing phagocytosed microbes. These findings were part of the formative era of cell biology and initiated the modern study of endocytosis and cell-mediated resistance to infection. Cohn further explored the endocytic apparatus in pioneering studies of the mouse peritoneal macrophage in culture. He described vesicular inputs from the cell surface and Golgi apparatus and documented the thoroughness of substrate digestion within lysosomal vacuoles that would only permit the egress of monosaccharides and amino acids. These discoveries created a vigorous environment for graduate students, postdoctoral fellows, and junior and visiting faculty. Some of the major findings that emerged from Cohn's collaborations included the radioiodination of the plasma membrane for studies of composition and turnover; membrane recycling during endocytosis; the origin of the mononuclear phagocyte system in situ; the discovery of the dendritic cell system of antigen-presenting cells; the macrophage as a secretory cell, including the release of proteases and large amounts of prostaglandins and leukotrienes; several defined parameters of macrophage activation, especially the ability of T cell-derived lymphokines to enhance killing of tumor cells and intracellular protozoa; the granule discharge mechanism whereby cytotoxic lymphocytes release the pore-forming protein perforin; the signaling of macrophages via myristoylated substrates of protein kinase C; and a tissue culture model in which monocytes emigrate across tight endothelial junctions. In 1983, Cohn turned to a long-standing goal of exploring host resistance directly in humans. He studied leprosy, focusing on the disease site, the parasitized macrophages of the skin. He injected recombinant lymphokines into the skin and found that these molecules elicited several cell-mediated responses. Seeing this potential to enhance host defense in patients, Cohn was extending his clinical studies to AIDS and tuberculosis. Zanvil Cohn was a consummate physician-scientist who nurtured the relationship between cell biology and infectious disease.(ABSTRACT TRUNCATED AT 400 WORDS)

gCap39 is a nuclear and cytoplasmic protein

gCap39 is a newly identified member of the Ca(2+)- and polyphosphoinositide-modulated gelsolin family of actin binding proteins which is different from gelsolin in several important respects: it caps filament ends, it does not sever filaments, it binds reversibly to actin, it is phosphorylated in vivo, and it is also present in the nucleus. gCap39 and gelsolin coexist in a variety of cells. To better understand the roles of gCap39 and gelsolin, we have compared their relative amounts and intracellular distributions. We found that gCap39 is very abundant in macrophages (accounting for 0.6% of total macrophage proteins), and is present in 12-fold molar excess to gelsolin. Both proteins are highly induced during differentiation of the promyelocytic leukemia cell line into macrophages. gCap39 is less abundant in fibroblasts (0.04% total proteins) and is present in equal molar ratio to gelsolin. The two proteins are colocalized in the cytoplasm, but gCap39 is also found in the nucleus while gelsolin is not. Nuclear gCap39 redistributes throughout the cytoplasm during mitosis and is excluded from regions containing chromosomes. Our results demonstrate that gCap39 is a nuclear and cytoplasmic protein which has unique as well as common functions compared with gelsolin.

African swine fever virus attachment protein

Treatment of African swine fever virus particles with nonionic detergents released proteins p35, p17, p14, and p12 from the virion. Of these proteins, only p12 bound to virus-sensitive Vero cells but not to virus-resistant L or IBRS2 cells. The binding of p12 was abolished by whole African swine fever virus and not by similar concentrations of subviral particles that lacked the external proteins. A monoclonal antibody (24BB7) specific for p12 precipitated a protein that, when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the absence of 2-mercaptoethanol, showed a molecular mass of 17 kDa (p17*) instead of 12 kDa as found in the presence of 2-mercaptoethanol. The relationship between these two proteins was confirmed by the conversion of p17* to p12 when the former was isolated from polyacrylamide gels in the absence of 2-mercaptoethanol and subsequently treated with the reducing agent. The supernatant obtained after immunoprecipitation with the p12-specific antibody lacked the virus-binding protein.

Biochemical analysis of synoviocytes from normal and arthritic rats. Evidence for an activated state associated with adjuvant polyarthritis

Adjuvant-induced polyarthritis in rats is a common model system used for the study of the synovitis that occurs in rheumatoid arthritis. Synoviocytes A, the major cell type covering the internal surface of the joint, could be involved in the pathogenesis of rheumatoid arthritis because of their increased proliferation and the intraarticular manifestations of the disease. So far only a few molecular studies have been reported on synoviocytes upon arthritis induction. We report here changes in polypeptides, between control and arthritic synoviocytes, by using two different radiolabeling methods and two-dimensional gel electrophoresis analysis. Major differences were found using metabolic labeling on regions of tropomyosins, cyclin, tubulins and vimentin. In addition, external surface labeling of the cells with lactoperoxidase showed clear differences between control and arthritic synoviocytes in the region of 77-100-kDa proteins. Some of these differences can be reproduced by certain macrophage activators such as phorbol myristate acetate and lipopolysaccharide acting on synoviocytes in vitro and in vivo respectively. These results exclude the possibility that the changes observed were due to a possible infiltration of other cell types in the arthritic synovia and strongly support the existence of an activated state of synoviocytes associated with arthritis induction.

Glycoprotein profiles of macrophages at different stages of activation as revealed by lectin binding after electrophoretic separation

Glycoprotein profiles of rat macrophages (M phi) at different stages of activation were studied by examining the reactivity of various lectins to the glycoproteins separated by polyacrylamide gel electrophoresis. Ricinus communis agglutinin 1 (RCA1) revealed several components including glycoproteins of Mr 160 kDa and 65 kDa prominent in resident M phi. A pokeweed mitogen (PWM) isolectin, Pa-4, recognizes branched poly(N-acetyllactosamine)-type carbohydrate chains, and revealed a significant increase in glycoproteins of Mr ranging from 70 kDa to 150 kDa on thioglycolate-elicited M phi. Increased reactivity of PWM to thioglycolate-elicited M phi was observed by direct binding of 125I-labeled Pa-4 to intact or glutaraldehyde-fixed M phi. Histochemical staining of formaldehyde-fixed M phi in vitro with biotinylated Pa-4 was consistent with the gel analysis, that is, resident M phi had no reactivity while thioglycolate-elicited M phi showed slight reactivity. Alveolar and intratumoral M phi bound more Pa-4 than resident or thioglycolate-elicited M phi. The PWM isolectin may therefore serve as a marker for an early stage of M phi activation.

Changes in the expression of cell surface sialoglycoproteins during transition of human monocytes into macrophages

Cell surface sialoglycoproteins of human mononuclear phagocytes in different maturation stages were labelled by the periodate/borohydride method and separated by SDS-polyacrylamide gel electrophoresis. The main surface glycoproteins of peripheral blood monocytes had molecular masses of 115 and 95 kDa. During in vitro transition into adherent macrophages, the monocyte-characteristic surface glycoproteins disappeared. Most of the changes in the surface glycoprotein pattern occurred during the first 24 h and after 96 h the changes were completed. The major sialoglycoproteins of the macrophage cell surface had molecular masses of 130 and 55 kDa. The macrophage cell surface showed further changes when cultured in the presence of synovial fluid (10%). These results may reflect the in vivo maturation of monocytes into tissue macrophages. In synovium, tissue-derived factors may also take part in differentiation.

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.

Glycolipids of the mouse peritoneal macrophage. Alterations in amount and surface exposure of specific glycolipid species occur in response to inflammation and tumoricidal activation

We have characterized the major glycolipid constituents of the mouse peritoneal macrophage, and have demonstrated that alterations in the amount and in the accessibility of specific glycolipid species to galactose oxidase/NaB3H4 labeling, an indicator of glycolipid surface exposure, occur in response to inflammation and as a consequence of activation to a tumoricidal state. The key findings are: (a) Asialo GM1, a major neutral glycolipid constituent of all macrophage populations examined, is accessible to galactose oxidase/NaB3H4 labeling on the surface of TG-elicited and BCG-activated macrophages but not on resident macrophages; (b) GM1 is the predominant ganglioside constituent of the mouse macrophage. Resident macrophages contain two distinct GM1 species, as determined by cholera toxin binding, while TG-elicited and BCG-activated macrophages contain an additional GM1 species. Differences in the relative amounts of these GM1 species, as well as in their accessibility to galactose oxidase/NaB3H4 labeling, exist among the macrophage populations. These observations suggest that both a chemical and spatial reorganization of surface glycolipids occurs in response to inflammation and tumoricidal activation.

Synthesis of complement by macrophages and modulation of their functions through complement activation

During the last decade considerable progress has been made to characterize intimate functional links between macrophages, a major cellular component of immunoinflammatory responses, and the complement system representing the major humoral mediator of inflammation. Macrophages of various species and tissue sites have been shown to synthesize and release most of the complement components providing these cells with their own "pericellular" complement system. Circumstantial evidence for the assembly of both classical and alternative pathway convertases has been adduced. An intricate network of feedback loops involving endogenous and extrinsic factors operates to adjust complement production to acute requirements, for example augmenting production in the face of accelerated turnover at sites of inflammation, and returning it to baseline levels once the inflammatory stimulus has subsided, in order to maintain a fine-tuned balance. The molecular mechanisms underlying regulation of complement synthesis by macrophages are beginning to be elucidated by use of gene technology. On the other hand, complement activation products exert a number of effects on macrophages via specific surface receptors causing internalization of offending agents, microbes, and immune complexes, promotion of intracellular killing, controlling migration behavior, inducing release of potent biologic substances such as lysosomal enzymes, arachidonic acid metabolites, and interleukin 1. In these interactions, two important humoral mediator systems of inflammation, the complement system and the arachidonic acid cascade, are functionally linked at the level of the macrophage. Stimulation of the release of immunomodulating compounds from macrophages invoke a role for complement in immune regulation. This multifaceted interplay is of particular importance considering the mobility of macrophages that allows them to gain almost unrestricted access to sites of ongoing immunoinflammatory responses. The time seems to have come to abandon the petrified thinking in socalled systems as, for instance, humoral versus cellular, specific versus unspecific, and to proceed to interlocking functions guided by physiology proper.

Uptake of transferrin by rat peritoneal macrophages

Activated rat peritoneal macrophages bind 125I-apotransferrin in a time- and temperature-dependent process, the amount of transferrin taken up at 4 degrees C amounting to only about 15% of that bound at physiological temperatures. Binding is reversible, saturable, and largely abolished by prior treatment of the cells with Pronase. A single class of high affinity binding sites is evidenced by Scatchard analysis, each cell binding about 110 000 apotransferrin molecules with an apparent affinity constant of 1.4 x 10(6) l mol-1. Macrophages are also capable of binding about one-third as much iron-saturated transferrin as iron-free transferrin. Since binding of neither form of the protein is influenced by the presence of the other, separate and independent binding sites for apotransferrin and iron transferrin are presumed to exist on the macrophage.

Establishment of a hybridoma secreting a monoclonal antibody specific for activated tumoricidal macrophages

New activated macrophage-specific antigen (AcM.1) detected by a monoclonal antibody has been described. The AcM.1 antigen was only detectable on activated macrophages induced by pyran and Corynebacterium parvum but not on resident or thioglycollate medium (TGC), proteose-peptone, and mineral oil-elicited macrophages, and not on blood monocytes and neutrophils. Activated macrophages induced by pyran and C. parvum, as expected, exhibited tumor cytotoxicity, whereas TGC-elicited macrophages did not show any cytotoxicity. Moreover, pretreatment of pyran-activated peritoneal exudate cells with AcM.1 antibody plus complement abolished approximately 80% cytotoxicity. Thus, this AcM.1 antigen detected by a monoclonal antibody is the first unique marker of activated tumoricidal macrophages and should provide a useful probe for investigating the mechanisms of activation or differentiation of macrophages.

Biosynthesis of membrane factor B by mouse peritoneal macrophages

The biosynthesis of many of the complement proteins by cells of the monocyte-macrophage series has been established. Studies on these cells using radiolabelled amino acids demonstrated synthesis of precursor proteins (pro-complement), and the native complement protein similar in size to that found in the plasma. However, synthesis of membrane complement proteins has not been demonstrated, although it has been suggested by previous studies using indirect techniques. In particular, there is evidence for the membrane-associated factor B in human lymphocytes. We report here that resident and thioglycollate-stimulated mouse peritoneal macrophages synthesized, in short-term primary cultures membrane factor B of molecular weight (MW) 95,000 and secreted factor B (MW 90,000) as single chain polypeptides. We also found a large single chain polypeptide with an approximate molecular weight of 195,000, which may be the putative factor B precursor.

Down-regulation of mannosyl receptor-mediated endocytosis and antigen F4/80 in bacillus Calmette-Guérin-activated mouse macrophages. Role of T lymphocytes and lymphokines

Bacillus Calmette-Guerin (BCG) infection alters the surface and endocytic properties of mouse peritoneal macrophages (PM) compared with thioglycollate- elicited (TPM) or resident PM (RPM). Expression of Ia antigen (Ag) is enhanced up to fourfold, but plasma membrane receptors that mediate binding and uptake of mannosyl/fucosyl-terminated glycoconjugates (MFR), Fc receptors, and the macrophage (mphi)-specific Ag F4/80 are reduced by 50-80 percent. Levels of Mac-1 remain relatively stable. These changes are accompanied by enhanced secretion of O(2)(-), after further stimulation with phorbyl myristate acetate, and of plasminogen activator. Both these products are released by TPM, but not RPM. The characteristic surface phenotype of BCG-PM can also be induced by injection of C. parvum, another mphi- activating agent, but not by thioglycollate broth, lipopolysaccharide, or proteose peptone. Purified protein derivative (PPD) and N-acetylmuramyl-L- alanyl-D-isoglutamine. 2H(2)0 are soluble agents with partial activity. Alteration of mphi markers by BCG infection depends on T lymphocyte function, although studies with nude mice indicate that other pathways may also serve to modify the surface of the mphi. Mphi from uninfected animals displayed all markers of activation after adoptive transfer of specifically-sensitised lymphocytes with PPD, intraperitoneally, or after co- cultivation. Treatment of primed lymphocytes with anti-Thy-1 antibody and complement ablated this effect. Lymphokines obtaned by Ag or mitogen stimulation induced similar changes in TPM and RPM. Mannose-specific endocytosis decayed rapidly, time 1/2 approximately equal to 16 h and stabilized at approximately 25 percent of control values. Single-cell analysis showed that residual MFR activity was uniform in the target population. Loss of Ag F4/80 after activation by lymphocyte and PPD was less marked than after infection (35 percent vs 80 percent), unlike MFR activity, which declined to a similar extent. Induction of mphi Ia by lymphokine reached a peak after 2-3 d and was lost within 2 d of its removal. Recovery of MFR and F4/80 was incomplete under these conditions. These studies establish that activated mphi known to display enhanced antimicrobial/anticellular activity express markedly different surface properties distinct from elicited or resident cells. The role of antigen- stimulated T cell products in regulating mphi function is confirmed, and down-regulation of mannosyl-receptor-mediated endocytosis provides a sensitive, quantitative, and cell-specific new marker to study their properties and mechanism of action. Extensive, but selective remodeling of mphi plasma membrane structure could play an important role in controlling recognition and effector mechanisms of the activated mphi.

Identification of phagocytosis-associated surface proteins of macrophages by two-dimensional gel electrophoresis

Two-dimensional PAGE (P. Z. O'Farrell, H. M. Goodman, and P. H. O'Farrell. 1977. Cell. 12:1133-1142) has been employed to assess the effects of antibody-dependent phagocytosis on the cell surface protein composition of RAW264 macrophages. Unilamellar phospholipid vesicles containing 1% dinitrophenyl-aminocaproyl-phosphatidylethanolamine (DNP-cap-PE) were used as the target particle. Macrophages were exposed to anti-DNP antibody alone, vesicles alone, or vesicles in the presence of antibody for 1 h at 37 degrees C. Cell surface proteins were then labeled by lactoperoxidase-catalyzed radioiodination at 4 degrees C. After detergent solubilization, membrane proteins were analyzed by two-dimensional gel electrophoresis. The resulting pattern of spots was compared to that of standard proteins. We have identified several surface proteins, not apparently associated with the phagocytic process, which are present either in a multichain structure or in several discretely charged forms. After phagocytosis, we have observed the appearance of two proteins of 45 and 50 kdaltons in nonreducing gels. In addition, we have noted the disappearance of a 140-kdalton protein in gels run under reducing conditions. These alterations would not be detected in the conventional one-dimensional gel electrophoresis. This evidence shows that phagocytosis leads to a modification of cell surface protein composition. Our results support the concept of specific enrichment and depletion of membrane components during antibody-dependent phagocytosis.

Priming of macrophages for enhanced oxidative metabolism by exposure to proteolytic enzymes

Preincubation for 10-30 min with trypsin, pronase, chymotrypsin, or papain primed macrophages to undergo a twofold to sixfold increase in oxidative metabolism, measured as release of superoxide anion or hydrogen peroxide, during stimulation by phorbol myristate acetate or ingestion of Candida parapsilosis. Preincubation of macrophages with inactivated proteases, nonenzyme proteins, or neuraminidase did not affect their oxidase response. Exposure of macrophages to proteases generated at sites of inflammation could prime these cells for a more effective oxidase response to phagocytosis or for greater tissue damage from release of toxic oxygen metabolites.

Degradation of connective tissue matrices by macrophages. III. Morphological and biochemical studies on extracellular, pericellular, and intracellular events in matrix proteolysis by macrophages in culture

We have shown that macrophages in culture degrade the glycoproteins and amorphous elastin of insoluble extracellular matrices. Ultrastructural observation of the macrophage-matrix interaction revealed that connective tissue macromolecules were solubilized from the matrix extracellularly. At least part of the matrix breakdown was localized to the immediate vicinity of the cells, as shown by morphological and biochemical studies, although the rate of degradation correlated closely with the secretion of proteinases by various inflammatory stimuli in vivo, by glucocorticoids, prostaglandin E2 or colchicine, or by phagocytosis of latex, zymosan, or cholesterol-albumin complexes in culture was reflected in altered rates of glycoprotein and elastin degradation by the macrophages. Alteration of endocytosis and lysosomal digestion by cytochalasin B, NH4Cl, and proteinase inhibitors did not decrease the overall rate of matrix solubilization, but reduced the processing of the matrix fragments to peptides. Therefore, extracellular, pericellular, and lysosomal events each contribute to degradation of extracellular matrix macromolecules by inflammatory macrophages.

Macrophage component gp160, a major trypsin-sensitive surface glycoprotein

Macrophages secrete a large number of proteases, implying in vivo exposure of the cell surface to proteolytic conditions. Mild trypsin treatment of 125I-labeled guinea pig peritoneal macrophages preferentially cleaves one surface component of apparent 160,000 mol wt. Similar trypsin treatment of macrophages with 3H-labeled carbohydrate surface moieties also cleaves a single 3H-labeled 160,000 mol wt glycoprotein, referred to as gp160. Nonreducing sodium dodecyl sulfate (SDS)-electrophoresis established that gp160 of trypsinized cells remains assembled in the membrane as a multichain disulfide-bonded molecule. gp160 was purified by detergent extraction, L. culinaris lectin affinity chromatography and DEAE-cellulose chromatography. The corresponding molecule from trypsinized cells was purified by the same procedure. Reducing SDS-electrophoresis of purified trypsinized 125I-labeled gp160 revealed two proteolytic fragments with apparent molecular weights of 85,000 and 71,000. Thus, mild trypsin treatment of macrophages preferentially cleaves a single surface protein, possibly at a single site. Because the two fragments of gp160 are accessible to lactoperoxidase and trypsin, both must be exposed on the membrane surface. The reactive carbohydrate site was found on the 85,000 mol wt fragment, which alone contains the 3H-label introduced into intact cells by neuraminidase, galactose, oxidase, and [3H]KBH4.