Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have examined the Fc- and complement-receptor function of resident and thioglycollate-elicited mouse peritoneal macrophages plated on surfaces coated with rabbit antibody-antigen complexes and with complement. We derive four major conclusions from these studies. (a) The trypsin-resistant Fc receptors of resident and thioglycollate-elicited macrophages are completely modulated when these cells are plated on rabbit antibody-antigen complexes. Residual Fc receptor activity is a result of the incomplete modulation of trypsin-sensitive IgG2a receptors. (b) The complement receptors of thioglycollate-elicited macrophages, but not of resident macrophages, are modulated when these cells are plated on complement-coated surfaces. The capacity of the two cell types to modulate their complement receptors is correlated with their ability to ingest complement-coated erythrocytes. (c) The complement and Fc receptors of both types of macrophages move independently of one another. (d) Complement masks the Fc segments of IgG in immune complexes thereby rendering them ineffective as ligands for macrophage Fc receptors.
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PMID:Effects of immobilized immune complexes on Fc- and complement-receptor function in resident and thioglycollate-elicited mouse peritoneal macrophages. 38 78

Direct comparison of the effector cells mediating natural killer (NK) activity against mouse tumor cells and antibody-dependent cell-mediated cytotoxicity (ADCC) against mouse tumor target cells coated with alloantisera indicated that NK cells and K-cells (effector cells mediating ADCC) may belong to the same subpopulation of lymphocytes, but they have a different mechanism of killing. Effector cells mediating NK activity and ADCC were nonadherent, nonphagocytic Fc receptor-bearing cells that sediment at 3.5-4.5 mm/hour. Treatment with anti-Thy 1.2 serum in the absence of complement resulted in an increase of NK activity, whereas this treatment caused a substantial loss in ADCC. Both NK activity and ADCC were equally sensitive to the in vivo or in vitro effects of X-irridiation. In vivo inoculations of high doses of hydrocortisone resulted in a reduction of NK activity, but ADCC was not affected. NK cells were trypsin-sensitive, with a profound decrease in the cytolytic activity being observed in a 4-hour 51Cr release assay. The activity, however, could be recovered after overnight incubation at 37 degrees C. Trypsin treatment did not inhibit ADCC as measured by the 18-hour assay.
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PMID:Correlation between natural and antibody-dependent cell-mediated cytotoxicity against tumor targets in the mouse. II. Characterization of the effector cells. 38 12

The Fc receptor (FcR) on human lymphocytes is studied by using soluble immune complexes in antigen excess, prepared between ferritin and rabbit anti-ferritin, and a modification of Coombs' antigolbulin reaction (double-coating indirect rosette formation). 12% of human blood lymphocytes are shown to have Fc receptors. The FcR on lymphocytes is sensitive to pronase treatment, partially sensitive to trypsin digestion, and is inactivated after short glutaraldehyde fixation of lymphocytes. By cell fractionation experiments, FcR-positive lymphocytes were enriched in cell populations enriched with B cells.
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PMID:Fc receptors on human lymphocytes detected with double-coating indirect rosette formation. 44 2

Immunochemical studies of murine thymus-leukemia antigens (TLA) have confirmed that the subunit structure consists of a 45,000-dalton heavy chain and a beta 2 microglobulin (beta 2m) light chain. Similar structural features are exhibited by the TLA from thymocytes of Tlaa, Tlac, Tlad, and a leukemia cell derived from C57BL/6, a Tlab strain. In addition to the similar subunit structure from the four haplotypes, each TLA shows a similar pattern of trypsin proteolysis. This procedure yields a major heavy chain cleavage product of approximately 37,000 daltons that remains associated with beta 2m and retains most or all of the antigenic determinants of the intact TLA. Evidence is presented that TLA do not exhibit Fc receptor properties, nor do they adsorb to murine leukemia virus antigens under the conditions of isolation for analysis on polyacrylamide gel electrophoresis (PAGE) in sodium dodecyl sulfate (SDS). Taken together these findings strongly support the hypothesis that TLA comprise a family of chemically similar antigens belonging to a structurally and genetically related group that includes H-2D, H-2K, and Qa-2,3.
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PMID:Shared chemical properties of different murine thymus-leukemia antigens. 44 10

Staphylococcus aureus protein A (SPA) acts as a mitogen stimulating DNA synthesis and is not antagonistic to the mitogenic activity of other mitogens. The mitogenicity of SPA is due to the protein's multivalent Fc antibody receptors. Partial trypsin digestion of SPA yields monovalent Fc antibody receptors which are not mitogenic. Using a thymidine incorporation assay, results indicated that tryptic digests of SPA added to mouse splenic leukocytes 12 hours after stimulation with either concanavalin A, lipopolysaccaride or SPA suppressed the DNA synthesis normally elicited by these mitogens. SPA was digested with 1% trypsin at pH 8 for varying periods of time. As the digestion time increased from 0 to 60 minutes the mitogenicity of the SPA-trypsin digests decreased indicating cleavage from multivalent to monovalent SPA Fc antibody receptors. The decrease in mitogenicity of the SPA digests was directly associated with increased ability to inhibit DNA synthesis in mitogen stimulated leukocytes. A proposed mechanism for the inhibition of DNA synthesis suggests that SPA-monovalent Fc antibody receptors mimic cellular Fc receptor function thereby influencing cellular gene expression.
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PMID:Suppression of DNA synthesis in mitogen stimulated leukocytes with partial trypsin digests of Staphylococcus aureus protein A. 53 78

Evidence is presented concerning the existence on mouse peritoneal macrophages of two separate and distinct Fc receptors, one for cytophilic monomeric IgG (mIgG) and the other for polymeric IgG. The latter Fc receptor recognizes both heat-aggregated IgG and antigen-complexed IgG. The major findings of our studies are: (a) the different susceptibility of the two Fc receptor types by pronase, trypsin or phospholipase C; (b) the independent modulation of these two binding sites on the cell membrane; (c) the inability of mIgG to inhibit the binding of particulate antigen-complexed IgG ligand; (d) the ability of mIgG molecules which are devoid of the cytophilic property to attach to the macrophage surface upon their polymerization induced by heating or antigen. The results are discussed in terms of "cytophilic" and "opsonic" Fc receptor types which may provide different functional abilities for normal macrophages.
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PMID:IgG-binding sites on macrophage cell membrane. I. Identification of two distinct Fc receptors on mouse peritoneal macrophages. 54 79

Radioiodinated normal rabbit IgG was used to detect Fc receptors on the surface of HeLa S3-2 cells infected with herpes simplex virus (HSV). Unlike the Fc receptors present on most leukocytes, these virus-induced Fc receptors were found to be sensitivite to trypsin at concentrations of enzyme as low as 0.1 mg/ml. Treatment of infected cells with neuraminidase enhanced the binding of IgG. Yet the HSV-induced Fc receptor(s) is probably a glycoprotein because its synthesis was inhibited by 2-deoxy-D-glucose at concentrations inhibiting glycoproteins but not total proteins. Binding of radioiodinated IgG to Fc receptors on infected HeLa S3-2 cells was unaffected by F(ab')2 fragments prepared from antisera against uninfected HeLa S3-2 cells or against human beta2-microglobulin. By contrast, anti-HSV F(ab')2 or Fab' fragments decreased binding of radioiodinated IgG to HSV-infected cells by 85%, and binding of radioiodinated Fc was also inhibited by anti-HSV Fab'.
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PMID:Fc receptors induced by herpes simplex virus. I. Biologic and biochemical properties. 68 55

A comparison was made of the activity of synovial fluid (SF) lymphocytes with peripheral blood lymphocytes in antibody-mediated and mitogen-induced lymphocyte cytotoxicity in patients with a variety of inflammatory joint diseases. SF lymphocytes consistently showed little or no antibody-mediated cytotoxicity (AMC) although mitogen-induced cytotoxic activity was comparable with that of the peripheral blood lymphocytes. Blocking substances on the cell surface were not responsible for the lack of AMC by SF lymphocytes as preincubation at 37 degrees C and enzyme treatment (trypsin, neuraminidase) of the cells did not restore activity. The lack of AMC by SF cells from a variety of inflammatory joint fluids demonstrates that this may be a consequence of inflammation in the joint and excludes the possibility that this is a specific property of fluids from certain conditions such as rheumatoid arthritis. Lymphocytes thought to be involved in AMC have a characteristic surface morphology (Fc receptor positive, E rosette negative, surface immunoglobulin negative). Such lymphocytes are present in synovial fluid in comparable proportions to those in blood. Hence the absence of AMC indicates that functional assays must be used in determining the presence or absence of cells with special functions.
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PMID:Lymphocyte studies in rheumatoid arthritis. II. Antibody-mediated and mitogen-induced lymphocyte cytotoxicity in synovial fluid and peripheral blood. 71 73

The receptor for FC(IgG) on chicken lymphoid cells was investigated by EA rosette techniques using sheep erythrocytes sensitized with a sub-agglutinating dose of anti-sheep erythrocyte (SRBC) chicken serum. Chicken lymphocytes did not form rosettes with SRBC coated with rabbit antibody, and human and mouse lymphocytes did not bind SRBC sensitized with chicken antibody. Only avian sera were effective in blocking the Fc receptor. Similarities between chicken and mammalian Fc receptors were demonstrated as both are pronase sensitive, trypsin resistant, and are distinct from surface immunoglobulin. Fc receptors were also distinguished from avian bursa- and thymus-specific antigens. Additional Fc receptor-bearing cells were revealed in bursa, spleen and bone marrow lymphocytes after neuraminidase treatment.
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PMID:Fc receptor-bearing lymphoid cells in the chicken. I. Characterization of the Fc(IgG) receptor. 74 17

With isolated subpopulations of human peripheral blood mononuclear cells, spontaneous cell-mediated cytotoxicity (SCMC) and antibody-dependent cellular cytotoxicity (ADCC) were demonstrated to be functions of a population of surface immunoglobulin (sIg)-negative, Fc receptor-positive lymphocytes. Organ distribution studies revealed that SCMC and ADCC effector cell activity occurred in parallel, being present in spleen and absent in tonsils. Treatment of effector cells with trypsin significantly inhibited SCMC but not ADCC and this inhibition was not reversed by short-term incubation in autologous plasma. These results demonstrate that SCMC and ADCC involve different cytotoxicity mechanisms and are consistent with two subsets of effector cells with separate functional capabilities or a single effector cell mediating both forms of cytotoxicity through separate mechanisms.
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PMID:Spontaneous cell-mediated cytotoxicity by human peripheral blood lymphocytes in vitro. 89 45


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