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PubMed1978

Lymphocyte subpopulations, serum immunoglobulins and complement factors in patients with atopic dermatitis.

The percentages of lymphocytes carrying different classes of membrane-bound Ig, and lymphocytes forming rosettes with sheep erythrocytes (E-RFC), as well as lymphocytes with receptor for the Fc-part of IgG (EA-RFC) were determined in 19 patients with atopic dermatitis. Lymphocyte suspensions were also stained with a specific rabbit anti-human T-lymphocyte antiserum. Furthermore, the serum concentration of IgG, IgA, IgM and IgE and the complement factors C3 and C4 were measured. A small but significant increase in lymphocytes with membrane-bound IgE and an increase in the serum concentration of IgE and complement factor C4 were observed. A decrease in the percentages of lymphocytes with receptors for sheep erythrocytes (E-RFC) was also found. The percentages of lymphocytes that stained with the anti-T antiserum correlated well with the percentages of lymphocytes forming rosettes with sheep erythrocytes. In one patient we found increased IgE positive lymphocytes, increased IgE serum concentration and a decreased T-cell number.

Adolescent↗
PubMed1986

CNBr cleavage of the light chain of human complement factor I and alignment of the fragments.

The light chain and heavy chain of reduced and alkylated human complement Factor I were purified by high-pressure gel-permeation chromatography. CNBr cleavage of Factor I light chain yielded four major fragments, which were purified by gel filtration. N-Terminal sequence analysis of the CNBr-cleavage fragments allowed identification of 200 of the approx. 240 amino acid residues of the light chain. An alignment is proposed, based on sequence analysis of peptides obtained after cleavage at arginine residues of the light chain and on homology of the sequence determined with that of other serine proteinases. The sequence around the active-site serine residue was established and three potential attachment sites for carbohydrate moieties were identified.

Amino Acid Sequence↗
PubMed1988

Two populations of complement factor H differ in their ability to bind to cell surfaces.

Using hydrophobic affinity chromatography on phenyl-Sepharose, human complement factor H can be separated into two subpopulations, phi 1 and phi 2. Although phi 1 and phi 2 are known to differ in their aggregation properties under non-physiological low ionic strength conditions, no difference in aggregation state was detected under the conditions used for cell-binding experiments. We have investigated these two subpopulations further to determine whether functional differences exist between them. The subpopulation phi 2 was found to bind specifically and saturably to the surface of Raji cells. The binding of the other subpopulation, phi 1, was low, and essentially non-specific. A monoclonal anti-factor H antibody, BGH-1, was raised which recognizes preferentially the phi 2 subpopulation and inhibits the binding of factor H to cell surfaces.

Antibodies, Monoclonal↗
PubMed1990

Identification and sequence analysis of four complement factor H-related transcripts in mouse liver.

Mouse liver RNA analyzed by Northern blotting with a full-length complement factor H cDNA probe demonstrates the 4.4-kilobase (kb) H mRNA as well as three additional hybridizing species of 3.5, 2.8, and 1.8 kb, respectively. Further characterization of these alternative transcripts was pursued by isolation of additional cDNAs from a liver library using a full-length H probe. Twelve clones homologous to but distinct from H were isolated, analyzed by restriction mapping, and divided into four classes, A, B, C, and D, based on their sequences. Clones from classes A, B, and C all contained nearly identical 5'-untranslated regions and leader sequences that differed from H at more than 50% of their nucleotide positions. The 5'-untranslated and leader sequences of the class D clone were unrelated to the corresponding regions of H or the class A, B, or C clones. The remaining portions of the H-related cDNAs were made up of short consensus repeats, 7 in class A, 4 in class B, 13 in class C, and 5 in class D. To determine the relationship between the H-related transcripts and the cDNA clones, Northern blots of liver RNA were analyzed by hybridization with two probes, one specific for the class D cDNA and the other reacting specifically with the class A, B, and C cDNAs. The class A/B/C probe detected transcripts of 3.5, 2.8, and 1.8 kb in liver RNA, and the class D probe hybridized to a distinct 1.8-kb message. Additionally, a cosmid genomic library was screened with H cDNA, and nine H-related clones were isolated. They spanned a region of approximately 120 kb, defining at least two discrete H-related gene loci. These results identify new members of the super-family of C3b/C4b binding protein genes.

Amino Acid Sequence↗
PubMed1990

Mapping of a retinoic acid-responsive element in the promoter region of the complement factor H gene.

Retinoic acid receptors are members of the steroid/thyroid hormone receptor superfamily. Pursuant to the discovery that dexamethasone increases complement factor H expression, we examined the effects of retinoic acid on this gene. Both H mRNA and protein levels are increased by retinoic acid in L cells. Using the luciferase reporter gene system we have identified a region of the H promoter required for the retinoic acid response. This region contains an imperfect palindrome of the TGACC motif, present in thyroid hormone and estrogen-responsive elements. We demonstrate specific binding of the retinoic acid receptor beta to this sequence of the H gene by DNA-protein gel retardation assay. Therefore, these studies extend the sphere of influence of the retinoids to complement, an intrinsic component of the humoral immune system.

Animals↗
PubMed1990

Bb fragment of bovine complement factor B: stimulation of the oxidative burst in bovine monocytes.

In a previous study, we reported that fragment Bb of bovine complement factor B activated bovine monocytes, as demonstrated by the uptake of 3H-deoxyglucose. In the present study, the effects of Bb on the production of superoxide anion and hydrogen peroxide by bovine monocytes was investigated. The production of superoxide was measured by the superoxide dismutase inhibitable reduction of cytochrome c. The change in absorbance was determined by a spectrophotometer at a wavelength of 550 nm. Hydrogen peroxide production was measured by the horse-radish peroxidase-dependent oxidation of phenol red. The resulting color change was measured by a spectrophotometer at a wavelength of 620 nm. Fragment Bb (20 micrograms/mL) induced the generation of 0.96 +/- 0.2 (mean +/- SEM) nanomoles of superoxide/2.5 x 10(5) monocytes at 5 min. The production of superoxide peaked at 15 min (1.24 +/- 0.3 nanomoles). The production of hydrogen peroxide was also rapid: 0.195 +/- 0.05 nanomoles/2.5 x 10(5) monocytes at 5 min with a peak at 15 min (0.250 +/- 0.04 nanomoles). These observations show that fragment Bb, which has serine protease activity, induces bovine monocytes to generate reactive oxygen intermediates such as superoxide and hydrogen peroxide.

Animals↗
PubMed1987

The homology of complement factor C8 gamma chain and alpha-1-microglobulin.

The sequence of the complement factor C8 gamma chain shares a remarkable degree of similarity with that of alpha-1-microglobulin, a member of the alpha-2u-globulin superfamily. This superfamily comprises a diverse group of distantly related animal proteins possessing characteristic structural features and similar functions. Comparison of the C8 gamma chain with these proteins supports its homology to them and suggests a possible functional role.

Alpha-Globulins↗
PubMed1992

Complement factor 9 deficiency in serum of human neonates.

The serum concentration of complement factor C9 (C9) was 260 +/- 47 micrograms/ml (+/- SE) in 14 mothers and less than 42 micrograms/ml in each of their 14 neonates. During incubation for 60 min, 11 of 14 maternal sera and 3 of 14 neonatal sera reduced the survival of Escherichia coli O7w:K1:NM to less than 20% of the original inoculum (P less than .03). Eleven neonatal sera did not kill the bacteria. Supplemental C9 (60 micrograms/ml) enhanced the bactericidal capacity of 10 neonatal sera. 125I-labeled C9 was deposited onto E. coli by neonatal sera, but less efficiently than by pooled adult sera. Supplemental IgG enhanced 125I-labeled C9 deposition and potentiated the bactericidal activity of exogenous C9. Therefore, neonatal sera contained diminished concentrations of C9 and killed E. coli inefficiently. In neonatal sera, supplemental C9 was deposited onto E. coli and enhanced bactericidal activity. These effects of C9 were potentiated by supplemental IgG.

Adult↗
PubMed1988

Regulation of complement factor H synthesis in U-937 cells by phorbol myristate acetate, lipopolysaccharide, and IL-1.

The capacity of the human monocyte cell line U-937 to synthesize complement factor H was examined. The kinetics of secretion of factor H into cell culture supernatant were followed by a sensitive solid phase RIA capable of measuring 0.1 ng of protein. Daily secretion of factor H was low and almost linear and was approximately 3 ng of factor H per 10(6) cells. Factor H synthesis was inhibited by cycloheximide but returned to the levels seen in untreated cultures after removal of the inhibitor. LPS and IL-1 both effected a time- and dose-dependent enhancement of factor H synthesis. Induction of U-937 cells with PMA to differentiate into macrophage-like cells also resulted in increased factor H synthesis. RIA of cell lysates, immunofluorescence microscopy, as well as FACS analysis all revealed that factor H Ag was also associated with the U-937 cell membrane. The population of U-937 cells bearing membrane-associated factor H was decreased from 77 to 43% after stimulation for 48 h with LPS (1 microgram/ml). [35S]Methionine metabolic labeling and SDS-PAGE analysis of factor H immunoprecipitates from unstimulated and stimulated culture supernatants and cell lysates demonstrated a major polypeptide, m.w. 150,000, and a minor component, m.w. 42,000. Western blot analysis of factor H in fresh normal plasma also detected both 150,000 and 42,000 m.w. factor H proteins. This is in agreement with the recent demonstration of a 4.4- and 1.8-kb mRNA for factor H in human liver. These data demonstrate that U-937 cells synthesize factor H that is structurally and antigenically similar to factor H in normal plasma. The exact nature of the membrane-bound factor H and its functions and mechanism of attachment to the cell membrane remain to be elucidated.

Cell Line↗
PubMed1987

Sequence analysis of a cDNA clone encoding the C-terminal end of human complement factor H.

Peptide sequencing of the complement system regulatory protein, factor H, permitted the synthesis of a mixed sequence oligonucleotide probe. Human liver cDNA libraries were screened and factor H-specific clones selected. No full-length clone was obtained, but the largest available clone, R2a, was found to encode the C-terminal 657 amino acids of factor H. The derived amino acid sequence consists of 10 contiguous internally homologous segments, each about 60 amino acids long. Sequences homologous to these are found in several other complement and non-complement proteins. Such sequences are likely to represent a particular type of tertiary structure subunit.

Amino Acid Sequence↗
PubMed1991

Complement factor D-like activity of Porphyromonas gingivalis W83.

Porphyromonas gingivalis is a proteolytic gram-negative anaerobic bacterium that is frequently isolated from lesions of human periodontal disease. Previous studies have shown that P. gingivalis strain W83 inactivates C3 in pooled normal human serum (NHS) by a mechanism that is inhibitable by EDTA, yet it degrades purified complement proteins by a mechanism that is not EDTA-inhibitable. Furthermore, during complement activation, only a small number of C3 molecules accumulate on the surface of this organism unless the bacteria are treated with the protease inhibitor TLCK prior to complement activation. The hypothesis was tested that P. gingivalis W83 contains protease activity mimicking that of complement factor D, thus enabling it to activate C3 in serum without significant C3 accumulation on the cell surface. It was first noted that incubation of P. gingivalis W83 in absorbed human serum that was depleted of factor D resulted in C3 consumption that was reversed in the presence of the protease inhibitor TLCK. To directly demonstrate that factor B-dependent C3 consumption occurs in the absence of factor D, P. gingivalis W83 was incubated with purified C3 or a mixture of C3 and B. Although some proteolysis of C3 was noted, increased C3 consumption was noted in mixtures containing both C3 and B. This increment in C3 consumption was inhibited by both EDTA and TLCK. Furthermore, the addition of purified factor H to this mixture inhibited the increment in C3 consumption, indicating that a C3 convertase was probably formed.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatography, Gel↗
PubMed1992

In vitro biosynthesis of complement factor I by human endothelial cells.

We have studied the secretion of the complement regulatory protein factor I by human umbilical vein endothelial cells (HUVEC). Northern and Western blot analysis and biosynthetic labeling experiments indicate that HUVEC secrete factor I at very low levels in basal conditions and that this secretion is significantly enhanced by interferon-gamma. Analysis of the proteolytic inactivation of C3b by HUVEC supernatants show that factor I is secreted in a functional form and can promote the specific proteolytic inactivation of C3b to iC3b. Together with previous studies establishing the secretion of complement factor H by HUVEC, this work demonstrates that the endothelial cell is able to secrete in its environment two complement regulatory proteins, factor I and factor H, which can mediate the degradation of C3b to iC3b. The secretion of factor I by HUVEC provides a useful in vitro model to analyze the modulation of this secretion and may be relevant to the local deposition of iC3b at the surface of the endothelium during the inflammatory reaction.

Cells, Cultured↗
PubMed1991

Human complement factor H: molecular cloning and cDNA expression reveals variability in the factor H-related mRNA species of 1.4 kb.

Previously, we have shown that three different mRNA species of 4.3 kb, 1.8 kb and 1.4 kb, related to human complement factor H, are constitutively expressed in the human liver. Probing with our cDNA clone H-46 which represents 920 bp of the 3' end of the 4.3 kb mRNA of factor H on human liver RNA, we always detected the 4.3 kb and the additional, abundantly expressed mRNA species of 1.4 kb in length, indicating that the 1.4 kb transcript is highly homologous to the 3' end of the classical factor H mRNA of 4.3 kb. Using H-46 as a probe, several cDNA clones were isolated from a liver cDNA library and sequenced. The open reading frame of the novel mRNA species encodes a peptide consisting of five internal short consensus repeat motifs (SCR), identifying the translational product to be a member of the SCR family. Sequence comparison with cDNA clones derived from liver RNA of a different donor provided evidence for variability in the factor H related proteins encoded by the 1.4 kb mRNA species. Interestingly, this variability was found to be restricted to the three carboxyterminal SCR domains. Expression data indicate that our variant is not recognized by the monoclonal antibody 3D11.

Amino Acid Sequence↗
PubMed1991

Human complement factor H. Tissue specificity in the expression of three different mRNA species.

Using cDNA clones H-19 and H-46, we have shown previously that three different mRNA species (4.3 kb, 1.8 kb and 1.4 kb) for complement factor H are expressed constitutively in human liver. Here we report data suggesting that the expression of these different factor-H mRNA species is regulated by tissue-specific control mechanisms. Total RNA and poly(A)-enriched RNA from various human tissues (heart, lung, temporal cortex, kidney, spleen, bone marrow and muscle) various cell lines (HepG2, HepG3, HepG4, Hep3B, H-4, Jurkat, Molt4, H-9, KHos24Os, A-431, U937, Mono Mac 6 and Raji) and from primary cultures of peripheral blood monocytes, fibroblasts and human umbilical vein endothelial cells (HUVEC) were investigated for the expression of factor-H mRNA. In RNA preparations from extrahepatic tissue, factor-H mRNA was only detected in biopsies from the lung. Using 20 micrograms total RNA isolated from all 13 cell lines it was not possible to detect any factor-H mRNA, while mRNA for factor H was expressed in monocytes, HUVEC and fibroblasts. When expressed in extrahepatic tissues, only the 4.3-kb and the 1.8-kb mRNA species were detected, while the 1.4-kb mRNA is expressed abundantly in liver. Interferon-gamma did not induce the expression of factor-H mRNA in any of the cell lines tested. On the other hand, tumour necrosis factor-alpha induced the expression of the 4.3-kb mRNA species in U937 cells. In HUVEC and fibroblasts the relative quantities of the 4.3-kb and the 1.8-kb mRNA species and the regulatory effects of interferon-gamma, interleukin-1, dexamethasone and retinoic acid on their expression showed significant tissue specificity.

Blotting, Northern↗
PubMed1989

Inhibition of complement-factor-5a-induced inflammatory reactions by prostaglandin E2 in experimental meningitis.

The possible role of complement factor 5a (C5a) and prostaglandin E2 (PGE2) in cerebrospinal fluid (CSF) pleocytosis and protein accumulation was assessed in a rabbit model of meningitis. Intracisternally administered C5a caused a rapid, early influx of leukocytes into CSF that peaked at 1 h after injection; by 6 h, cell counts were slightly higher than those in controls. Administration of PGE2 or saline did not induce detectable CSF leukocytosis. Coadministration of PGE2 with C5a decreased CSF leukocytosis in a dose-related fashion. Protein concentration increased 30 min after administration of C5a, peaked after 1 h, and remained elevated for 6 h. PGE2 caused a dose-related increase in protein content after 2 h, whereas coadministration caused an inversely dose-related inhibition of the C5a-induced protein influx into CSF. These data suggest that PGE2 in the subarachnoid space exerts an inhibitory action on the C5a-mediated response that is probably not related to its direct effects on protein extravasation.

Animals↗
PubMedDate not supplied

Localization of the properdin factor complement locus Pfc to band A3 on the mouse X chromosome.

The locus for properdin (properdin factor complement, Pfc), a plasma glycoprotein, has been mapped to band A3 of the mouse X chromosome by in situ hybridization to metaphase spreads containing an X;2 Robertsonian translocation. The X-linkage of the locus has also been confirmed by analysis of Mus musculus x Mus spretus interspecific crosses. The XA3 localization for Pfc places it in the chromosomal segment conserved between man and mouse which is known to contain at least six other homologous loci (Cybb, Otc, Syn-1 Maoa, Araf, Timp).

Animals↗