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Results for “Immunoglobulin Fc Fragments”

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At least 19 recordsLinked to original sources
PubMed1992

Differentiation of species in human beta-haemolytic group G streptococci using immunoglobulin Fc fragment receptor.

AIMS: To assess the ability of human immunoglobulin Fc fragment binding activity to differentiate human biotype large colony group G streptococci from the group G "Streptococcus milleri group". METHODS: Fifty two isolates of large colony group G streptococci and 30 group G "S milleri group" strains were tested for their ability to bind fluorescein conjugated human IgG Fc fragments after acetone fixation. Immunoblotting with peroxidase labelled human Fc fragments after resolution of bacterial polypeptides by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was performed for six large colony strains. RESULTS: All large colony group G streptococci showed positive Fc fragment binding whereas all "S milleri group" bacteria failed to bind Fc fragments when viewed by fluorescence microscopy. All six large colony strains showed similar immunoblot binding patterns. CONCLUSION: Immunoglobulin Fc fragment receptor content distinguishes the large colony group G streptococci from the group G "S milleri group" and mayhave a role in the rapid laboratory diagnosis of pharyngeal pathogens.

Child↗
PubMed1980

Interactions among rheumatoid synovial cells and monocyte-macrophages: production of collagenase-stimulating factor by human monocytes exposed to concanavalin A or immunoglobulin Fc fragments.

Adherent synovial cells (ASC) were obtained from minced synovium from patients with rheumatoid arthritis by dissociating the lining cells from the extracellular matrix and dispersing them with proteases. These cells produce high levels of latent collagenase in primary culture. With passage of ASC, collagenase levels decrease but can be stimulated by a soluble factor (MCF) released in vitro from cultured human blood monocyte-macrophages. Monocyte cultures exposed to aggregated immunoglobulin, Fc fragments of immunoglobulin or concanavalin A (Con A) increase production of MCF several-fold more than the control cultures. MCF production by monocytes exposed to Fab fragments does not differ from controls. Although aggregated immunoglobulin, Fc fragments, and Con A stimulate PGE2 synthesis and secretion by human monocytes, the effects on MCF production are not mediated by PGE2 since concentrations of indomethacin that completely block PGE2 production do not inhibit MCF production. These findings of increased production of MCF by monocytes in response to substances that probably exert their effects via surface receptors could be relevant in interpreting the in vivo role of immune complexes in diseases associated with connective tissue destruction.

Arthritis, Rheumatoid↗
PubMedDate not supplied

[T-lymphocytes with a receptor for the immunoglobulin Fc fragment in the blood of multiple sclerosis patients].

In 12 multiple sclerosis patients and 15 healthy subjects the suppressor activity in vitro by the method of Shou et al. was determined parallelly with the number of T-lymphocytes with the receptor for the Fc fragment of immunoglobulin G (TG lymphocytes). In healthy subjects a correlation (p less than 0.05) was demonstrated between the suppressor activity of lymphocytes in vitro and the number of TG lymphocytes in the peripheral blood. On the other hand, in multiple sclerosis patients a decrease was observed frequently in the suppressor activity of these cells in vitro (especially during exacerbation of the disease) while the number of TG lymphocytes in the peripheral blood was normal or raised sometimes. Different causes of the this phenomenon in multiple sclerosis are discussed.

Adult↗
PubMed2004

Hierarchical formation of disulfide bonds in the immunoglobulin Fc fragment is assisted by protein-disulfide isomerase.

Antibodies provide an excellent system to study the folding and assembly of all beta-sheet proteins and to elucidate the hierarchy of intra/inter chain disulfide bonds formation during the folding process of multimeric and multidomain proteins. Here, the folding process of the Fc fragment of the heavy chain of the antibody MAK33 was investigated. The Fc fragment consists of the C(H)3 and C(H)2 domains of the immunoglobulin heavy chain, both containing a single S-S bond. The folding process was investigated both in the absence and presence of the folding catalyst protein-disulfide isomerase (PDI), monitoring the evolution of intermediates by electrospray mass spectrometry. Moreover, the disulfide bonds present at different times in the folding mixture were identified by mass mapping to determine the hierarchy of disulfide bond formation. The analysis of the uncatalyzed folding showed that the species containing one intramolecular disulfide predominated throughout the entire process, whereas the fully oxidized Fc fragment never accumulated in significant amounts. This result suggests the presence of a kinetic trap during the Fc folding, preventing the one-disulfide-containing species (1S2H) to reach the fully oxidized protein (2S). The assignment of disulfide bonds revealed that 1S2H is a homogeneous species characterized by the presence of a single disulfide bond (Cys-130-Cys-188) belonging to the C(H)3 domain. When the folding experiments were carried out in the presence of PDI, the completely oxidized species accumulated and predominated at later stages of the process. This species contained the two native S-S bonds of the Fc protein. Our results indicate that the two domains of the Fc fragment fold independently, with a precise hierarchy of disulfide formation in which the disulfide bond, especially, of the C(H)2 domain requires catalysis by PDI.

Animals↗
PubMed1981

Use of F(ab')2 antibody fragments in the synthesis of immunoadsorbents for preparing monospecific antigen.

Class specific F(ab')2 antibody fragments were prepared by pepsin digestion of the labile Fc immunoglobulin fragments in antigen--antibody precipitates. The F(ab')2 fragments were covalently coupled to cyanogen bromide-activated Sepharose 4B and the resultant immunoadsorbent used to isolate IgG from human serum with a single chromatographic step, in high yield and purity and negligible non-specific interaction. This technique affords a simple method for preparing an enriched source of class specific affinity-purified immunoglobulin antibodies suitable for many immunochemical applications.

Antibody Specificity↗
PubMed1995

The enhancement of the human immunoglobulin G Fc fragment-binding activity of Mycoplasma salivarium cells by trypsin treatment is ascribed to the binding of trypsin to the Fc fragment.

Human immunoglobulin G Fc fragment-binding activity of Mycoplasma salivarium cells was remarkably enhanced by trypsin treatment of the cells. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile of proteins of the cells treated with trypsin was the same as that of the cells treated with pronase, although pronase treatment had been shown to reduce the activity in our previous study (FEMS Microbiol. Lett. 123, 305-310, 1994). This contradiction was clarified by the finding that trypsin bound the Fc fragment more strongly than the cells, and a small amount of trypsin remained in the cells treated with trypsin and washed well. On the basis of these results, it was concluded that the enhancement of cell activity by trypsin treatment was ascribed to binding of the Fc fragment to trypsin remaining in the trypsin-treated cells.

Immunoglobulin Fc Fragments↗
PubMed1979

Staphylococci-induced human platelet injury mediated by protein A and immunoglobulin G Fc fragment receptor.

Bloodstream infections with staphylococci are accompanied by thromboembolic complications. We have studied the mechanism of the interaction of staphylococci with human blood platelets. Staphylococci that possess protein A, a bacterial receptor for the Fc fragment of immunoglobulin G (IgG), caused aggregation of human platelets in whole plasma accompanied by release of [(3)H]serotonin. These reactions were time and concentration dependent, requiring two or more staphylococci per platelet to give maximal response within 5 min. The interaction between staphylococci and platelets required the presence of cell wall-bound protein A and of IgG with an intact Fc fragment. It did not require an intact complement system. Cell wall-bound protein A (solid phase) was capable of aggregating human platelets in whole plasma. In contrast, free, solubilized protein A (fluid phase) did not cause measurable aggregation, and release of [(3)H]serotonin was reduced. An excess of free, solubilized protein A blocked aggregation of human platelets induced by staphylococci in whole plasma. The role of the Fc fragment of IgG in the staphylococci-human platelet interaction was demonstrated by an experiment in which free, isolated Fc fragment blocked aggregation of platelets in whole plasma induced by staphylococci. Furthermore, binding of (125)I-protein A to human platelets was demonstrated in the presence of complete IgG with intact Fc fragment but not in the presence of the F(ab)(2) fragment. Binding of the protein A-IgG complex to the human platelet Fc receptor was paralleled by the release of [(3)H]serotonin. These results represent a novel example of the interaction of two phylogenetically different Fc receptors, one on prokaryotic staphylococci and the other on human platelets. Their common ligand, IgG, is amplified by one Fc receptor (protein A) to react with another Fc receptor present on human platelets, which results in membrane-mediated aggregation and release reaction occurring in whole plasma. This mechanism can be of significance in the pathomechanism of thromboembolic complications at the site(s) of intravascular staphylococcal infection.

Binding Sites↗
PubMed1990

Aggregated immunoglobulin and Fc fragment of IgG induce IL-6 release from human monocytes.

The Fc fragment of immunoglobulin (Ig) has been shown to play an important role in the regulation of humoral immunity, cellular immunity, lymphocyte and monocyte activation, and immune mediator secretion. We wished to determine if Ig or Fc fragments would induce IL-6 production from monocytes. Incubation of monocytes purified from human peripheral blood mononuclear cells with aggregated Ig or Fc fragments of Ig induced interleukin-6 (IL-6) activity in the supernatants. Monomeric Ig taken from an intravenous preparation of Ig, from which all aggregated Ig are removed, would not induce IL-6 production from monocytes whereas as a heat-treated aliquot, presumably containing aggregates, did induce IL-6. The supernatants were assayed according to their ability to induce growth in a murine hybridoma cell line B9, or enhance Ig secretion of B cells stimulated with Staphylococcus aureus Cowan 1 (SAC). The IL-6 activity in the supernatants could be neutralized by a polyclonal rabbit anti-human IL-6 antiserum in both assays of IL-6 activity. Exposure of T-enriched or B-enriched lymphocyte subpopulations to Fc fragments did not induce the release of any IL-6 after 12 hr of incubation, but small amounts of IL-6 were produced by B-enriched cells after 60 hr of exposure to Fc fragments. Hence Fc fragments and aggregated Ig induce peripheral blood monocytes to rapidly secrete large quantities of interleukin-6.

Animals↗