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PubMed1986

Regulation of class III major histocompatibility complex gene products by interleukin-1.

Interleukin-1 (IL-1) is a product of mononuclear phagocytes that mediates changes characteristic of the response to inflammation or tissue injury (the acute-phase response). One of two structurally and functionally homologous major histocompatibility complex (MHC) class III genes encodes a positive acute-phase protein, complement factor B. The closely linked complement C2 gene is not affected during the acute-phase response. Purified human IL-1, pH 7.0, and recombinant-generated murine IL-1, pH 5.0, increased the expression of factor B and other positive acute-phase proteins in human hepatoma cells but decreased the expression of albumin, a negative acute-phase reactant. Furthermore, in a murine fibroblast L-cell line transfected with cosmid DNA bearing the human C2 and factor B genes, IL-1 mediated a reversible dose- and time-dependent increase in factor B expression in the transfected cells. Expression of the C2 gene was not affected by IL-1. The effect of IL-1 on factor B expression involves a mechanism acting at a pre-translational level as demonstrated by an increase in specific messenger RNA content and a corresponding increase in biosynthesis and secretion of factor B. The structural basis and mechanism for selective and independent regulation of these genes provides insight into the molecular control of the inflammatory response.

Animals↗
PubMed1977

Influence of serum-derived chemotactic factors and bacterial products on human neutrophil chemotaxis.

The chemotaxis of neutrophils has been shown to be modulated by serum factors, tissue factors, bacterial products, and a host of other substances. In vivo, these factors may act in concert with each other to modify neutrophil movement. We examined the effect of aggregated gamma globulin-activated serum (AS), bacterial factors, and endotoxin either alone or in combination with each other, on human neutrophil chemotaxis. Exposure of neutrophils to AS resulted in deactivation to AS but not to Escherichial coli or Staphylococcus epidermis culture filtrate. Exposure of neutrophils to S. epidermis or E. coli CF or E. coli endotoxin resulted in deactivation to AS or C5a but not to E. coli or S. epidermis culture filtrate. Addition of endotoxin to AS or C5a resulted in inhibition of chemotaxis by untreated neutrophils toward this combination as compared with AS alone. These results suggest that separate mechanisms may be involved when serum or bacterial chemotactic factors initiate human neutrophil chemotaxis. Furthermore, the potent but specific inhibitory effect of endotoxin on chemotaxis toward AS may be of clinical significance.

Blood↗
PubMed1992

Legionella pneumophila lipopolysaccharide activates the classical complement pathway.

Legionella pneumophila is a gram-negative bacterium capable of entering and growing in alveolar macrophages and monocytes. Complement and complement receptors are important in the uptake of L. pneumophila by human mononuclear phagocytes. The surface molecules of L. pneumophila that activate the complement system are unknown. To identify these factors, we investigated the effects of L. pneumophila lipopolysaccharide (LPS) on the classical and alternative complement pathways of normal human serum by functional hemolytic assays. Although incubation of LPS in normal human serum at 37 degrees C resulted in the activation of both pathways, complement activation proceeded primarily through the classical pathway. Activation of the classical pathway by LPS was dependent on natural antibodies of the immunoglobulin M class that were present in various quantities in sera from different normal individuals but were absent in an immunoglobulin-deficient serum obtained from an agammaglobulinemic patient. Additional studies using sheep erythrocytes coated with LPS suggested that the antibodies recognized antigenic sites in the carbohydrate portion of LPS. The ability of LPS to interact with the complement system suggests a role for LPS in the uptake of L. pneumophila by mononuclear phagocytes.

Complement C1↗
PubMed1994

Type C retrovirus inactivation by human complement is determined by both the viral genome and the producer cell.

The inactivation of type C retroviruses by human serum may be a considerable impediment to the use of retroviral vectors in vivo for gene therapy. Here we show that virus inactivation is dependent both on the virus and on the cell line used to produce the virus. All viruses produced from murine NIH 3T3 or dog Cf2ThS+L- cells are sensitive to human serum. In contrast, those produced from mink Mv-1-Lu and human HOS or TE671 cells are at least partially resistant, with the exception of murine leukemia viruses. In particular, the feline endogenous virus RD114 is completely resistant to a panel of eight human sera when produced from Mv-1-Lu or HOS cells. This differential resistance is controlled by the viral envelope proteins. Virus inactivation can be correlated with the ability of the producer cells to be lysed by human serum. Inactivation of sensitive viruses requires the classical pathway of complement but does not require virion lysis.

3T3 Cells↗
PubMed1994

HLA-B alleles and complotypes in Mexican patients with seronegative spondyloarthropathies.

OBJECTIVES: To analyse major histocompatibility complex (MHC) haplotypes in Mexican mestizo patients with seronegative spondyloarthropathies (SSpA) and normal controls, to discover if there are other antigens, besides B27, in the HLA region that might show association with the disease. METHODS: The study included 100 Mexican mestizo patients with SSpA and 200 of their first degree relatives. These groups were compared with 85 ethnically matched controls. The class I and class III MHC antigens were obtained by standard methods. The significance of differences between patients and controls was tested by chi 2 analysis; linkage disequilibrium among the different alleles in each haplotype was estimated by computing delta values. RESULTS: We found a significantly increased frequency of the HLA-B27 antigen (pcorr. = 1 x 10(-5), odds ratio (OR) = 33.4, 95% confidence interval (CI) = 9.3-142.0). In the group of 45 SSpA patients negative for the B27 antigen, independent increased frequencies of HLA-B49 antigen (pcorr. = 0.03, OR = 6.5, 95% CI = 1.5-32.8)) and the FC31 complotype (pcorr. = 0.04, OR = 3.7, 95% CI = 1.2-11.1) were found. Significant delta values were obtained for the [B27;SC30] haplotype (p = 0.0005) but not for haplotypes marked by the FC31 complotype. HLA-B antigens on the homologous chromosome in B27 positive patients were mainly HLA-B51 (18%) and HLA-B60 (16%); however, the observed genotypes B27/B51 and B27/B60 were not significantly different than expected from the allele frequencies alone. CONCLUSIONS: These data suggest that in Mexicans additional genes within the MHC region besides the HLA-B27 antigen, might be related to the genetic susceptibility for developing SSpA. Relevant antigens included the HLA-B49 and the FC31 complotype.

Adult↗
PubMed1975

Complement.

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Anaphylaxis↗
PubMed1983

Infections and hypocomplementemia.

The complement system, phagocytic leukocytes, and antibodies constitute the "department of defense" in the battle against infections caused by pyogenic microorganisms. Complement components are capable of directly killing (by lysis) certain susceptible bacteria and are the source of chemotactic peptides and heat-labile opsonin, which facilitate recognition and killing of microbes by phagocytic cells. When these vital functions are compromised, as in individuals with inherited deficiencies of complement components, the result is unusual susceptibility to severe infections.

Complement Activation↗
PubMed1986

Inherited complement component abnormalities.

Inherited deficiencies of early complement components are frequently associated with immune/rheumatic disorders and recurrent (Neisserial) infection with deficiency of late complement components. The genetic complexity of complement components is further demonstrated by electrophoretic allotypy and analysis of DNA restriction fragment length polymorphisms.

Adult↗
PubMed1975

Interaction of collagen with serum complement: inhibition of complement-mediated hemolysis.

Collagens from various vertebrate tissues were tested for their ability to consume complement (C) activity upon incubation in human serum or with isolated components of complement. 10 of 12 collagens tested had anticomplementary activity. The heat-denatured form of collagen, gelatin, was found weakly anticomplementary, but elastin was found inactive in the interaction with C. Inactivation of C is a reaction which is dependent on the time of incubation and the collagen concentration and partially dependent on the temperature of incubation. Most collagens depleted C from human serum in presence of cation chelators, EDTA and EGTA, whereas the large part of anticomplementary activity of soluble collagens obtained from rat skin was abolished in presence of EDTA. Evidence is presented that two different principles in collagens play a role in inactivation of C. A factor, contained in insoluble collagens and inhibitable by mild oxidation with periodate, inactivates C1 directly even in presence of chelating agents. Another principle, contained in soluble and insoluble collagen and resistant to periodate treatment, depletes C in serum by utilization of C via the alternate pathway (the C3 shunt).

Animals↗
PubMed1976

Inactivator of the first component of human complement (C1INA). Enhancement of C1INA activity against C1s by acidic mucopolysaccharides.

Acidic mucopolysaccharides enhanced C1INA activity against C1s. The presence of heparin in the reaction mixture of C1INA and C1s markedly enhanced the inactivation of C1s by potentiating C1INA activity. Treatment of serum with C1s resulted in the inactivation of C4 hemolytic activity, but this inactivation of C4 by C1s was prevented by the presence of heparin presumably due to the enhancement of C1INA activity normally present in serum. The other acidic mucopolysaccharides, chondroitin sulfates A, B and C, were also effective on potentiating C1INA activity against C1s, but they were less active than heparin. The enhancement of C1INA activity by heparin was not observed in the reaction between C1INA and plasmin.

Chondroitin Sulfates↗
PubMed1980

Effect of aspirin on the complement system in vitro.

Aspirin (acetylsalicylic acid), ASA and sodium salicylate (NaSA) activate the complement system in vitro. The activation involves the components of the classical pathway. It is, however, antibody independent. Evidence for activation are (1) consumption of C and C component activities; (2) activation of C1 evidenced by release of C1s from the macromolecular complex, and (3) C3 and C5 conversion.

Aspirin↗
PubMed1987

Identification of a spontaneously shed fragment of B cell complement receptor type two (CR2) containing the C3d-binding site.

CR2 is a 140-kilodalton glycoprotein expressed on B lymphocytes which binds to both C3d and Epstein-Barr virus (EBV). The present study identified a 72-kilodalton C3d-binding protein (gp72) in the spent culture media of Raji B lymphoblastoid cells as a spontaneously shed fragment of the 140-kilodalton CR2 molecule. Both polyclonal and monoclonal antibodies (AB) were used in several assay systems to detect antigenic determinants shared between the gp72 fragment and CR2. Rabbit antibodies to either intact CR2 or gp72 blocked C3d receptor activity, and this inhibitory activity was removed by absorption of anti-CR2 with purified gp72.OKB7, a monoclonal anti-CR2 AB that blocks both C3d and EBV binding to CR2, reacted specifically with both CR2 and gp72, whereas both anti-B2 and HB-5 monoclonal anti-CR2 AB, that block neither of these receptor sites, were unreactive with gp72. The data suggested that the gp72 fragment was not present as such in intact cells, but rather was a product of cells generated by proteolysis of CR2. Thus, intrinsically labeled gp72 was isolated from Raji cell media by affinity chromatography on OKB7-Sepharose, but only intact CR2 was isolated from the Raji cell fraction solubilized in the presence of protease inhibitors. Several lines of evidence suggested that gp72 was not a second type of C3d receptor that was distinct from CR2. First, Raji cells expressed nearly identical amounts of OKB7 and HB-5 epitopes when analyzed by flow cytometry or radioimmune assay, excluding the possibility that B cells expressed OKB7 antigens in both CR2 and a distinct HB-5-negative C3d receptor. Second, all Raji cell surface C3d receptor activity was associated with HB-5-reactive CR2 molecules. We conclude that gp72 represents a spontaneously shed proteolytic fragment of CR2 that contains the C3d-binding site and the closely associated OKB7 epitope.

B-Lymphocytes↗
PubMed1980

Hereditary angio-oedema: its pathogenesis and management.

Hereditary angio-oedema is a genetically-determined disease. Usually the disease is due to a deficiency of C1-inhibitor or less commonly to the production of a functionally inactive molecule. The pathogenesis and clinical features of the disease are reviewed, and discussed in relation to the homeostatic role of C1 inhibitor. Finally the therapeutic approach to the disease is described and the scientific bases for the newer therapeutic discussed.

Anabolic Agents↗
PubMed1979

Serum complement levels in infancy: age related changes.

Levels of eight complement components and two control proteins, were determined on cord serum from normal full term neonates and serum from healthy infants aged 1 and 6 months. For all proteins, the levels were below the adult normal at birth and rose toward the adult range by age 6 months. In a second group of 271 patients, ages 1-36 months, serum Clq and properdin levels were measured. For both proteins, the mean values in early infancy were more than two SD below the adult range and did not reach the adult range until 18-21 months of age. The Clq concentration was more variable than that for any other component studied. In infants from 11 months-3 yr of age, Clq levels correlated with serum IgG levels, but properdin levels did not.

Adult↗
PubMed1995

Genetic deficiencies of complement.

Genetic deficiencies of proteins of the complement system are associated with diverse clinical phenotypes. These clinical manifestations vary as a function of the specific component that is missing. Molecular and cellular biological methods, coupled with more intensive clinical studies, have defined the pathophysiological basis for this set of genetic disorders. Insights into the normal function of complement and its role in immunopathology have been derived from the extensive work in this field during the past few years.

Complement C1↗