Adsorbed serum albumin is permissive to macrophage attachment to perfluorocarbon polymer surfaces in culture

Monocyte/macrophage adhesion to biomaterials, correlated with foreign body response, occurs through protein-mediated surface interactions. Albumin-selective perfluorocarbon (FC) biomaterials are generally poorly cell-conducive because of insufficient receptor-mediated surface interactions, but macrophages bind to albumin-coated substrates and also preferentially to highly hydrophobic fluorinated surfaces. Bone marrow macrophages (BMMO) and IC-21, RAW 264.7, and J774A.1 monocyte/macrophage cells were cultured on FC surfaces. Protein deposition onto two distinct FC surfaces from complex and single-component solutions was tracked using fluorescence and time-of-flight secondary ion mass spectrometry (ToF-SIMS) methods. Cell adhesion and growth on protein pretreated substrates were compared by light microscopy. Flow cytometry and integrin-directed antibody receptor blocking were used to assess integrins critical for monocyte/macrophage adhesion in vitro. Albumin predominantly adsorbs onto both FC surfaces from 10% serum. In cultures preadsorbed with albumin or serum-dilutions, BMMO responded similar to IC-21 at early time points. Compared with Teflon AF, plasma-polymerized FC was less permissive to extended cell proliferation. The beta(2) integrins play major roles in macrophage adhesion to FC surfaces: antibody blocking significantly disrupted cell adhesion. Albumin-mediated cell adhesion mechanisms to FC surfaces could not be clarified. Primary BMMO and secondary IC-21 macrophages behave similarly on FC surfaces, regardless of preadsorbed protein biasing, with respect to adhesion, cell morphology, motility, and proliferation.     

Are pregnancy-associated serum proteins responsible for the inhibition of lymphocyte transformation by pregnancy serum?

Certain pregnancy-associated serum proteins, namely pregnancy-associated alpha 2-glycoprotein, pregnancy-specific beta 1-glycoprotein, alpha-foetoprotein, human placental lactogen and human chroionic gonadotrophin, have been proposed as immunosuppressive factors. A pregnancy serum was constructed from a number of such sera to produce high serum levels of these compounds. Each of the proteins was then removed sequentially from the serum by affinity chromatography and the remaining materials examined for inhibitory activity on lymphocyte transformation. Only the removal of pregnancy-associated alpha 2-glycoprotein decreased suppression by the serum. However, a large proportion of the serum inhibitory activity could not be accounted for, indicating the presence of other suppressor factors.     

Modulation of human macrophage activity by Ascaris antigens is dependent on macrophage polarization state

Parasitic worms (helminths) are known to actively modulate host immune responses and inflammation. The aim of this study was to investigate if adult body fluid (ABF) from the helminth Ascaris suum has immunomodulatory effects on different subtypes of human monocyte-derived macrophages (M?) in vitro. M?s were exposed to A. suum ABF at different stages of their differentiation and/or polarization. M? were first differentiated from monocytes into either uncommitted (M-), classically activated (M(GM-CSF)) or alternatively activated (M(M-CSF)) phenotypes and then stimulated with lipopolysaccharide (LPS). ABF strongly suppressed LPS-induced TNF-α, IL-6 and IL-10 secretion in M(GM-CSF)s, however in M(M-CSF)s only TNF-α was suppressed, with these cells secreting high levels of IL-10 which was not affected by ABF treatment. To determine if ABF modulated the differentiation of previously uncommitted M? to either type 1 or type 2 M?, monocytes were differentiated with human serum into (M-)s and then polarized by IFN-γ/LPS or IL-4 treatment in the presence of ABF. Under these conditions, ABF did not modulate cytokine secretion but did reduce CD80 expression in IFNγ/LPS-polarized cells but not IL-4-polarized cells. Finally, we demonstrate that when monocytes are differentiated into M(GMCSF)s in the presence of ABF, subsequent inflammatory responses are markedly suppressed. Our data suggest that ABF inhibits cytokine secretion and co-stimulatory molecule expression in classically activated M? but not in alternatively activated M?, indicating selective action of ABF depending on M? subtype. Moreover, ABF appears to exert stronger activity when acting upon M? that have already been polarized to the type 1 phenotype, rather than influencing the polarization process per se.     

Production of macrophage activation factors by tryptic cleavage of calf serum proteins

Trypsin, when added to a bioassay for tumoricidal macrophages, produced killing of tumor cells. Trypsin cleaved fetal calf serum proteins to produce a protein fragment that activated macrophages to lyse tumor cells. Diisopropyl fluorophosphate-inhibited trypsin did not produce tumoricidal macrophages either by direct action on the macrophage or by action on serum proteins. The macrophage activation factors produced from serum proteins were fractionated into molecular weight ranges of 150,000, 68,000, and 30,000-5000. The effects of neutral proteinases and proteinase inhibitors on the ability of macrophages to lyse tumor cells is discussed.This study was supported by NSF grant PCM 8007869.     

Identification of soybean proteins responsible for respiratory allergies

Serum samples from 32 patients who suffered attacks during the asthma outbreaks of 1987 and 1988 in Cartagena, Spain, supposedly caused by soybean dust, were studied. At least 90% had specific IgE to shell components and only 13% showed specific IgE to shell-depleted soybean grains. A control group of 32 patients who also suffered asthma attacks but on different days from those of the outbreaks were negative. The shell's most important allergen with an apparent molecular weight of 8 kDa was not present in shell-depleted grains. This allergen as well as other less important shell allergens may be different from the allergens already identified by using serum from patients suffering food allergy to soya.     

Identification of serum and urine proteins responsible for enhanced pigment production by group B streptococci as amylases.

The serum and urine proteins responsible for enhanced pigment production in Streptococcus agalactiae in culture media were purified by chromatography and were identified as amylases by comparison of their amino acid composition with that calculated for proteins with known sequences. Similar pigment-enhancing activity was displayed by other amylases of nonanimal origin and by maltooligosaccharides.     

Adsorbed fibrinogen regulates the behavior of human dendritic cells in a CD18-dependent manner

The involvement of fibrinogen in inflammation has been considered by many, but the roles of the protein in that process have yet to be fully elucidated. The protein readily coats surfaces and is deposited at sites of inflammation. Furthermore, adsorbed fibrinogen influences many cells of the immune system, likely a result of increased receptor recognition upon ligand immobilization. To better understand adsorbed fibrinogen's role in inflammation, we studied the effects of the protein, adsorbed to the surface of microscopic beads, on human dendritic cells. Adsorbed fibrinogen increased dendritic cell expression of IL-6, IL-8, MIP-1beta and MCP-1. In contrast, solution phase fibrinogen had no effect. Importantly, dendritic cells formed complexes with, and subsequently accumulated around, beads in fibrinogen-dependent fashion. Antibodies directed against CD18 significantly decreased cytokine/chemokine expression and bead-cell complexation. Epsilon-aminocaproic acid limited bead-cell complexation, suggesting fibrinogen degradation products modulate dendritic cell activity. In support of this proposal, fibrinogen fragment D also increased MCP-1 expression by human dendritic cells. Taken together our data indicate adsorbed fibrinogen and its degradation products directly influence human dendritic cell operation. We propose a model whereby adsorbed fibrinogen plays a distinct causatory role in inflammation through its beta(2) integrin-mediated interaction with dendritic cells.     

CpG-oligodeoxynucleotide-stimulated chicken heterophil degranulation is serum cofactor and cell surface receptor dependent

Synthetic oligodeoxynucleotide containing unmethylated CpG motif (CpG-ODN) is immune stimulatory to chicken heterophils. Recognition of CpG-ODN by chicken heterophils leads to the mobilization and release of granules. This CpG-ODN-induced heterophil degranulation was chicken serum (CS)-dependent. Heat-denaturation and membrane filtration of CS revealed that the active serum cofactor(s) was likely a protein in nature with a molecule mass within 50,000 to 100,000. This serum cofactor(s) was heat-resistant at 56 degrees C for 1h. The involvement of a cell surface receptor in recognition of CpG-ODN was also demonstrated by (1) trypsin treatment of the heterophils abrogated the degranulation response and (2) CpG-ODN-induced heterophil degranulation was sensitive to the inhibition of Clathrin-dependent endocytosis. In addition, among various microbial agonists, including CpG-ODN, lipopolysaccharide, lipoteichoic acid, phorbol myristate acetate, and formalin-killed Salmonella enteritidis, CpG-ODN was the only agonist that displayed serum-dependent induction of degranulation in chicken heterophils. This is the first report that shows serum-dependent activation of leukocytes by CpG-ODN.     

Low serum conditions for in vitro generation of human macrophages with macrophage colony stimulating factor

Animal serum is often used to generate human macrophages in vitro. Since fetal calf serum (FCS) may complicate antigen uptake, processing and presentation on HLA molecules, we tested the ability of M-CSF to generate macrophages at low fetal calf serum conditions. Peripheral blood monocytes from 12 individuals were cultured 1-4 days with 0-100 ng/ml macrophage colony stimulating factor (M-CSF) at either 1 (low) or 5% (v/v) FCS. Regardless of number of days in culture, maximal (50-100 ng/ml) M-CSF stimulation and low FCS induced 65+/-5% esterase positive cells in all individuals compared to 52+/-7% without M-CSF (P<0.001). M-CSF increased the mean proportion of esterase positive cells after 24 or 96 h by 13% (P<0.005) and 13% (P<0.005), respectively, in 1% FCS, and 8% (P<0.05) and 2% (NS), respectively, in 5% FCS, indicating a slight negative interaction between 5% FCS and M-CSF (P<0.05). All cells were positive for CD14 and HLA class II, but cell number did not increase, confirming that M-CSF promote macrophage differentiation also at low FCS. M-CSF increased the average cell size after 24 or 96 h by 5.9+/-1.0 (P<0.05) and 8.6+/-0.5 (P<0.001) microm, respectively, without an increase in 5% FCS, further demonstrating the efficiency of M-CSF to promote macrophage generation at low FCS. The culture supernatants were negative for IL-1beta and TNF-alpha, which demonstrates that M-CSF did not activate the macrophages. The generation of human macrophages by M-CSF at low FCS should prove useful in studies where higher FCS concentrations may interfere with the assay.     

Adsorbed IgG: a potent adhesive substrate for human macrophages

Previous reports from our laboratory have demonstrated qualitatively that preabsorbed IgG can enhance long-term macrophage adhesion in vitro. This investigation further characterizes and quantifies the biological effect of adsorbed human IgG on human macrophages and probes the potential mechanisms. Ten-day human monocyte/macrophage cultures on Plastek M (PM), a normally poor cellular substrate for macrophages, confirmed the ability of preabsorbed IgG to dramatically enhance long-term macrophage adhesion. An adsorption solution concentration of 200 microg/mL of IgG was necessary to provide a consistent, optimal cellular response. (125)I adsorption studies indicated Langmuir-style IgG adsorption at low concentrations; however, no adsorption maximum was observed. Additional adsorption analysis revealed that the IgG fragments Fab, F(ab')(2), and Fc adsorb at levels only 20-40% that of the whole molecule. Despite the lower adsorption levels, both preabsorbed Fab and F(ab')(2) were shown to be as effective as whole molecule IgG at enhancing long-term macrophage adhesion. Surprisingly, the preabsorbed Fc fragment demonstrated no IgG-like activity, thereby eliminating the possibility of an Fc receptor-based mechanism. Other possible mechanisms, such as macrophage lectins, novel macrophage Fab receptors, and complement activation by adsorbed IgG and IgG fragments, are discussed.     

IgG subclass of human serum antibodies reactive with dietary proteins

Serum IgG antibodies reactive with different dietary proteins have been detected in a significant proportion of adult patients with coeliac disease, dermatitis herpetiformis and atopic eczema. Serum anti-milk antibodies were shown to be distributed predominantly between the IgG2 and IgG4 subclasses, whereas anti-gliadin antibodies in atopic eczema were predominantly of the IgG4 subclass. Furthermore, as antibodies to each of these dietary antigens in healthy adults were markedly restricted to the IgG4 subclass, their production may be part of a normal immune response to dietary proteins. There was no correlation between serum IgG4 antibody and total serum IgG4 level. In contrast, restricted IgG4 anti-gliadin antibodies were less prevalent in the serum of patients with coeliac disease and dermatitis herpetiformis, suggesting defective downstream switching of Ig heavy-chain genes in these conditions.     

The weak binding reaction between folate and human serum proteins

New evidence is presented that folic acid in serum binds with low affinity to major serum proteins. This low affinity binding is distinct from the high affinity binding by folate binding protein (FBP), a minor protein which is known to occur in serum with great quantitative variability. These conclusions are based on results obtained by equilibrium dialysis of serum containing only negligible amounts of FBP. At 4 degrees, the equilibrium value of the ratio of bound to free folate was approximately 0.81 and remained the same even wth up to 1,000 times greater than normal folic acid concentrations; however, with higher concentrations the ratio decreased progressively. These results are predicted by the laws of mass equilibria for a binding system with low ligand concentration vis-a-vis high binder concentration and low affinity between the reactants. A rough estimate of the mean affinity constant K governing this weak folate interaction with serum proteins yielded a value of 1.12 +/- 0.13 X 10(3) M-1.     

Proteolytic action of Legionella pneumophila on human serum proteins.

Proteolysis by four strains of Legionella pneumophila, the etiological agent of Legionnaires disease, was studied by the method of immunoelectrophoresis. Twenty-three human serum proteins were tested as substrates. Five proteins were degraded: alpha 1-acid glycoprotein, alpha 1-antichymotrypsin, beta-lipoprotein, beta 1E-globulin, and beta 2-glycoprotein-I. Moreover, the degradation of alpha 1-antichymotrypsin was demonstrated by investigation of an enzyme-blocking test. It is suggested that the proteolytic activity of L. pneumophila may bear some relationship to its pathogenic activity.