Search PubMed⌕ Search

Biomedical subjects

H R Colten

Publications and source records attributed to H R Colten.

At least 145 records · Page 8Linked to original sources
PubMed1981

Biosynthesis of complement components.

Many of the serum complement components are synthesized primarily in the liver but extrahepatic synthesis in mononuclear phagocytes has been noted. This local production of complement, particularly at sites of inflammation, may be of importance in host defenses and immunopathological reactions. Recent studies of complement biosynthesis in vitro have revealed some of the genetic and microenvironmental factors that affect the rates of complement synthesis, posttranslational modification, and secretion of these proteins. The third, fourth, and fifth complement components are synthesized as single chain, procomplement proteins that require proteolytic cleavage to generate the native C4 protein is mediated by a plasmin-like enzyme. These studies, plus the most recent developments in analysis of the complement genes at a molecular level, will provide more complete understanding the mechanisms of regulation of complement production.

Animals↗
PubMed1981

Characterization of the human complement (c3b) receptor with a fluid phase C3b dimer.

The interaction of C3b receptor with C3b, the major cleavage product of C3, elicits important biologic functions, such as enhanced phagocytosis and release of cellular enzymes. We determined the binding kinetics and binding isotherm of C3b-receptor interaction by using human cells and fluid phase C3b generated by trypsin cleavage of purified native C3. 125I labeled C3b was separated into 2 molecular species, a dimer and a monomer by column chromatography. We found that dimeric C3b bound to human erythrocyte C3b receptors with an affinity that was more than 25 times that of the monomer. 125I dimeric C3b did not bind to sheep red blood cells, which lack the C3b receptor, nor to trypsinized or 2-mercaptoethanol treated normal human red blood cells, 2 methods for abrogating the immune adherence activity. Binding of 125I fluid phase C3b dimer to the C3b receptor was specific, saturable (about 90 ng of C3b dimer bound maximally per 1 X 10(9) red blood cells), reversible (in the presence of a 100-fold molar excess of unlabeled ligand), and of moderate affinity (Kd about 9.53 nM). The equilibrium binding constants were similar with the various cells tested. Binding was characterized by rapid on and off rates and did not exhibit ligand cooperativity. This specific interaction reached a steady state within 10 to 15 min at 0 degrees C; 50% of specifically bound ligand dissociated from its binding site on human red blood cells in approximately 1 min at 0 degrees C. The density of C3b receptors on human red blood cells, polymorphonuclear leukocytes, monocytes, and B lymphocyte-enriched preparations was 360, 20,000, 30,000, and 21,000 receptors/cell, respectively.

Animals↗
PubMed1980

NH2-terminal sequence analysis of pro-C4, the precursor of the fourth component of guinea pig complement.

The amino acid sequence of the NH2-terminal regions of the intracellular precursor of the fourth component of guinea pig complement (pro-C4) and isolated alpha, beta, and gamma chains of native C4, synthesized by peritoneal macrophages in culture, were determined with a microradiosequencing technique. Radiolabeled pro-C4 was immunoprecipitated from cell lysates and native C4 from culture media which contained one of six 3H-amino-acids or [35S]methionine. The purity of these proteins was established and molecular weights were estimated by electrophoresis in sodium dodecyl sulfate. Seventeen of the first 22 residues of pro-C4 were identified. Fifteen of these 17 were nonpolar. The eight amino acids ascertained within the first 9 NH2-terminal residues of guinea pig pro-C4 were identical with those reported for human C4 beta chain, and identity with residues determined for guinea pig C4 beta chain was established. These data indicate that beta chain is the NH2-terminal segment of pro-C4, that no residues are cleaved from the NH2 terminus during the conversion to native C4, and that this segment of the pro-C4 molecule is conserved phylogenetically.

Amino Acid Sequence↗
PubMed1980

Hypogammaglobulinemia in patients with cystic fibrosis.

To investigate some aspects of immune function in cystic fibrosis, we measured serum immunoglobulins in 419 patients. Twenty-two per cent of the 154 patients less than 10 years old had hypogammaglobulinemia-G, whereas the older patients had normal or elevated serum immunoglobulins. A single mechanism accounting for the extraordinary prevalence of hypogammaglobulinemia in young patients with cystic fibrosis was not defined in studies of T and B-lymphocyte function in vitro or in studies of IgG metabolism in vivo. Analysis of objective clinical data, including arterial blood gases, chest roentgenograms, and bacteriologic cultures, indicated that the patients with hypogammaglobulinemia had significantly less severe lung disease than did age-matched patients with cystic fibrosis and normal or elevated IgG levels. We conclude that progression of lung disease may be due in part to a hyper-immune response.

Adolescent↗
PubMed1980

Specific modulation of complement-dependent human granulocyte function by imidazole acetic acid.

Because imidazole acetic acid (IAA), a product of histamine catabolism was shown to inhibit histaminase release from human polymorphonuclear leukocytes (PMNs), the effect of this compound on other neutrophil functions was investigated. IAA at concentrations of 10(-10) or more inhibited histaminase release induced by particle-bound C3b, the larger fragment of the activated form of the third component of complement. Release of histaminase induced by aggregated IgG, phorbal myristate acetate (PMA), formyl-methionyl-leucyl-phenylalanine (FMLP) and calcium ionophore was not affected by IAA. In addition IAA had no effect on release of beta-glucuronidase, myeloperoxidase, and lysozyme or on phagocytosis and superoxide generation. IAA did modestly inhibit neutrophil chemotaxis. These findings suggest a highly specific modulating effect of the histamine catabolite IAA on complement-mediated PMN function.

Acetates↗
PubMed1980

Control of complement synthesis and secretion in bronchoalveolar and peritoneal macrophages.

The effect of inflammation on C (C2 and C4) biosynthesis by bronchoalveolar and peritoneal cells was studied with methods that detect changes in synthesis rates and qualitative changes in cell populations. Adherent bronchoalveolar macrophages produced less C2 and C4 than adherent peritoneal macrophages. However, the subset of cells capable of producing C was more than 20-fold greater in the peritoneal cell population than in the population of bronchoalveolar cells. The rate of synthesis per C producing bronchoalveolar macrophage was 5 to 10 times the rate by C producing peritoneal macrophages. In contrast, the effect of an inflammatory stimulus on C production was the result of a change in rate of synthesis per cell, not a change in the proportion of C producing cells. This stimulatory effect was exerted locally, not on a cell population harvested from a distant site. At least two mechanisms for local control of C levels in tissues have been identified--that is, a change in synthesis rate and a qualitative change in macrophage cell population. The capacity to alter C levels at a site of inflammation may be important for C dependent functions in host defenses.

Animals↗
PubMed1980

Modulation of human monocyte functions by Fc fragments of IgG: a comparison to other monocyte 'activators'.

Human monocytes were maintained in tissue culture and the effect of various stimuli on their morphology and capacity to synthesize and secrete total protein, lysozyme, acid phosphatase, prostaglandin E and the second component of complement were determined. Human monomeric IgG, Fab fragments and albumin had no effect on the secretion of these products. However, addition of Fc fragments significantly decreased the synthesis of both lysosomal enzymes and the second component of complement and increased production of prostaglandin E. The addition of Con A to the monocyte monolayers resulted in a similar response. Latex particles slightly increased the secretion of acid phosphatase and C2, but had no effect on lysozyme secretion. Fc fragments also stimulated protein synthesis by monocyte monolayers cultured in serum-free medium. These 'activators' and endotoxin- or antigen-activated mononuclear cell supernatants (AMNS) resulted in varying degrees of increased spreading and adherence of the monocytes. The results of these studies suggest that the molecular species inducing the 'activated state' qualitatively and quantitatively determines the characteristics of the secretory response.

Acid Phosphatase↗
PubMed1979

Genetic defect in secretion of complement C5 in mice.

A genetic deficiency of the fifth (C5) component of complement1-3, a serum glycoprotein of molecular weight (MW) 220,000 (ref. 4), has been found in 39% of inbred strains of mice3. Sera of deficient mice lack detectable C5 activity and protein2,3. In addition deficient mice produce antibody to mouse C5 when injected with sera from C5 sufficient (normal) strains. Levy et al.5 showed that somatic cell hybrids between C5 deficient (B10.D2/old line) macrophages and either C5 sufficient (B10.D2/new line) mouse kidney or chicken erythroblasts secreted haemolytically active mouse C5 in vitro. Several possible molecular mechanisms to account for the findings were considered, but insufficient direct data were available to choose among them. We recently reported that mouse (CD.1 strain) peritoneal cells in culture synthesise and secrete a single chain precursor, pro-C5 (MW approximately 210,000), of the two-chain (alpha chain, 125,000 and beta chain 83,000 MW) C5 protein6. Radiolabelled precursor C5 was contained within the cells and was secreted into the tissue culture media. Using similar methods, we now find that C5 deficiency in each of five different mouse strains (AKR, SWR, DBA/2J8 A/HeJ and B10.D2/old line) is due to a failure in secretion of C5 protein and not to a failure in biosynthesis of pro-C5.

Animals↗
PubMed1979

Cutaneous necrotizing venulitis in patients with cystic fibrosis.

Palpable purpura was noted to occur late in the course of some patients with cystic fibrosis. Skin biopsy specimens showed necrotizing venulitis characterized by a perivenular infiltrate composed of neutrophilic leukocytes, fibrin, hypogranulated mast cells, and endothelial cell necrosis. Circulating immune complexes were detected. Recurrent pulmonary infections and the chronic administration of therapeutic agents provide sources of potential antigens.

Adolescent↗
PubMed1979

Complement-dependent histaminase release from human granulocytes.

The role of particle-bound complement proteins in the induction of noncytotoxic enzyme release from human granulocytes was investigated with the use of sera genetically deficient in complement and highly purified complement components. Release of histaminase, one of two important histamine catabolizing enzymes, and beta-glucuronidase from polymorphonuclear leukocytes was solely dependent on particle-bound C3b (the larger cleavage product of the third component of complement) when fluid-phase complement was excluded. The extent of enzyme release was a function of particle-bound C3b input, was reduced by exposing the particles to C3b inactivator, and was blocked by fluid-phase C3b. Phagocytosis of the C3b-coated particles was not required for enzyme release from neutrophils. In contrast, phagocytosis of "opsonized" particles was required for noncytotoxic release of histaminase and arylsulfatase from eosinophils; other proteins, as well as C3b, were able to opsonize particles for induction of enzyme release from eosinophils. These studies suggest a dual role for complement (particularly C3) in modulating vascular permeability phenomena, i.e., release of vasoactive mediators by the action of C3a and C5a, and release of the corresponding enzymes that inactivate the mediators by C3b.

Amine Oxidase (Copper-Containing)↗
PubMed1979

Cyclophosphamide and cortisone acetate inhibit complement biosynthesis by guinea pig bronchoalveolar macrophages.

To explore mechanisms of drug-induced alterations in local host defenses in the lung, the capacity of guinea pig alveolar macrophages to synthesize the second (C2) and fourth (C4) components of complement was studied following treatment with cyclophosphamide and cortisone acetate. Administration of either drug significantly inhibited biosynthesis of C2 and C4 within 1 day. After 1 week of treatment, local complement synthesis was inhibited approximately 80%, although serum levels of the corresponding proteins were normal.

Animals↗
PubMed1979

Biosynthesis and post-synthetic modification of a precursor (pro-C5) of the fifth component of mouse complement (C5).

Mouse peritoneal macrophages synthesized and secreted a precursor (pro-C5) of the fifth component of serum complement (C5) in short-term tissue culture. Approximately 0.2% of the newly synthesized intracellular protein and 0.8% of secreted protein were precipitable with antiserum to mouse C5. The precursor is similar in size to the native serum protein (210,000 daltons), but consists of a single polypeptide chain. In contrast, serum C5 consists of two polypeptide chains (m.w. 125,000 and 83,000) linked by disulfide bridges. An electrophoretic variant of pro-C5 distinct from intracellular C5 was detected in medium from macrophage cultures.

Animals↗