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PubMed1997

Systemic lupus erythematosus complicating complement type 2 deficiency: successful treatment with fresh frozen plasma.

We report a man who presented in 1981 at the age of 30 with cutaneous lupus erythematosus (LE), which was resistant to a range of treatments over the subsequent 11 years. In 1991 he suffered fits, dysphasia and agitated depression, and in 1992 a severe septicaemic illness. Systemic LE was diagnosed, and investigation showed homozygous complement type 2 deficiency (C2d). Over a period of 30 months he has received 6 weekly fresh frozen plasma. Since starting this treatment his cutaneous disease has resolved and his depression, verbal fluency and psychomotor scores improved. We have not observed any adverse effects to this treatment and suggest it should be considered in similar patients.

Adult↗
PubMed1984

Separation of functionally or highly pure C2 from human plasma with Sepharose and a lectin of Euonymus europeus.

A method is described for isolating both functionally and highly pure C2 from normal human serum or plasma. Functionally pure C2 was obtained by a two-step method of ammonium sulfate (AS) fractionation of plasma or serum and chromatography on AH-Sepharose containing a bound lectin of Euonymus europeus. The functionally pure C2 can be isolated in 2 days, and is used routinely as a reagent for functional hemolytic titrations of C3 and C4 in the Clinical Immunology Laboratory. Highly pure C2 was isolated by the two-step fractionation with AS followed by chromatography on CM-cellulose, aged CNBr-activated Sepharose 4B, and AH-Sepharose-lectin. The major difficulty for isolating highly pure C2 was its separation from Factor B of the alternative complement pathway. The yield of C2 varied from 30 to 40 per cent. Following electrophoresis and staining on polyacrylamide gels, the single band was hemolytically active C2.

Chromatography, Agarose↗
PubMed1987

A high frequency of inherited deficiency of complement component C4 in Darwin Aborigines.

A high frequency of serum complement component C4A deficiency may explain the higher prevalence and greater severity of systemic lupus erythematosus reported in Australian Aborigines. Inherited deficiencies of serum complement components C4A, C4B, and C2 were examined in two Australian Aboriginal populations from Darwin and Alice Springs and compared with the prevalence of complement deficiencies in white Australian blood donors. The frequency of C4A deficiency alleles was 29% in Darwin Aborigines compared with 12% in Alice Springs and 17% in Canberra blood donors. Partial C4B deficiency was also higher in Darwin Aborigines than in the other populations. Inherited deficiency of serum complement component C2 was not observed.

Alleles↗
PubMed1980

Hemolytic complement activity in normal human donor corneas.

Normal human donor corneas were minced into small fragments and eluted for 16 to 23 hours at 4 degrees C. The corneal eluates were then studied for hemolytic complement activity of C1, C4, C2, C3, C5, C6, and C7 with 50% hemolysis (CH50) of sensitized sheep RBCs. Sera from ten normal volunteers were also assayed for hemolytic complement activity in CH50 units per milliliter. For each complement component, the mean hemolytic activity in corneas was compared with the mean hemolytic activity in sera. These comparisons suggest that molecular weight may be a factor in determining the concentration of complement components in the cornea. The present study provides normal values of hemolytic complement activity for further studies of complement consumption in corneal diseases.

Adult↗
PubMed1997

Differential effects of cytomegalovirus infection on complement synthesis by human mesangial cells.

Viruses may be eliminated by the host immune system via complement-mediated lysis of infected cells. Previously, we have demonstrated that the synthesis of complement factor B by renal mesangial cells (MC) is enhanced by interferon-alpha (IFN-alpha), -beta and -gamma. In the present study we investigate the effect of human cytomegalovirus (HCMV) infection on the production of complement factors by MC. The production of factor B, C2, C4 and factor H by mock-infected MC was 0.2 +/- 0.4, 3.9 +/- 6.8, 1.7 +/- 0.8 and 149 +/- 36 ng/10(6) cells per 72 h, respectively. In HCMV-infected MC cultures an induction of both factor B and C2 protein synthesis was observed up to 2.2 +/- 1.1 and 156 +/- 74 ng/10(6) cells per 72 h, respectively. The synthesis of C4 and factor H of 2.9 +/- 2.0 and 146 +/- 31 ng/10(6) cells, respectively, was not altered significantly. By Northern blot and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis it was demonstrated that factor B and C2 mRNA expression were up-regulated in HCMV-infected cell cultures, whereas the levels of C4 and factor H mRNA were not changed. When MC cultures were inoculated with heat- or UV-inactivated HCMV no enhancement of factor B mRNA expression was observed. The enhanced expression was not blocked by phosphono acetic acid (PAA), suggesting that expression of the HCMV immediate early or early genes is sufficient to induce complement synthesis. We conclude that infection of MC cultures with HCMV selectively induces complement C2 and factor B production, probably mediated by interferons.

Blotting, Northern↗
PubMed1998

A targeted disruption of the murine complement factor B gene resulting in loss of expression of three genes in close proximity, factor B, C2, and D17H6S45.

Factor B is a serine protease, essential for the function of the alternative pathway of complement activation. To study further the importance of the alternative pathway of complement activation in vivo and to help elucidate any additional functions of factor B or its activation fragments we developed, by homologous recombination in embryonic stem cells, mice with a disrupted factor B gene. Factor B-deficient mice produced no detectable factor B mRNA or protein and had no detectable factor B enzymatic activity or alternative pathway function in their serum. Further studies revealed that the two adjacent genes, complement component C2 and D17H6S45, had been down regulated as a result of the disruption. The down-regulation of C2 gene expression was sufficient to cause a complete loss of classical pathway function as determined by the failure of sera from the deficient mice to opsonize antibody-sensitized sheep erythrocytes and by impairment of immune complex processing in vivo. The resulting mouse is deficient in both factor B and C2, and hence the alternative and classical pathways of complement activation, and adds to the repertoire of models for studying the in vivo role of complement in the immune system.

Animals↗
PubMed1980

Complement activation by commercial allergen extracts of cereal grains.

Commercial allergen extract preparations of whole cereal grains were examined in vitro for their reactivity with the human haemolytic complement cascade. Total haemolytic complement was consumed in a dose-dependent manner which did not correlate with the protein nitrogen content or bacterial endotoxin contamination of the extracts. Alternative pathway activation was shown by C3 conversion in the presence of EGTA while classical complement components C1, C4 and C2 were also much decreased in serum which was free of detectable specific antibody. Very small amounts of allergen extract initiated the formation of complement-dependent factors which were chemotactic for human polymorphonuclear leucocytes. These data suggest a potential for complement activation in vivo by ingestion, inhalation, or injection of cereal grain products.

Allergens↗
PubMed1998

Complement deficiency and autoimmunity.

Complete deficiency of one of the early components (C1, C4, or C2) of the classical pathway of the complement cascade is one of the strongest genetic risk factors for systemic lupus erythematosus that has been recognized. The lupus that occurs in complement-deficient individuals typically presents in early childhood. The association of complement deficiency and lupus has been known for over two decades, yet the explanation remains somewhat elusive. Complement component deficiencies may be associated with other rheumatic or autoimmune disorders and both partial and acquired complement component deficiencies are also associated with an increased risk of autoimmune disease. This article reviews the current understanding of the relationship between complement component deficiencies and autoimmunity. Recent data from animal models and new types of genetic analyses are reviewed.

Antibody Formation↗
PubMed1983

Relative importance of C4 binding protein in the modulation of the classical pathway C3 convertase in patients with systemic lupus erythematosus.

Serum concentrations of C1q, C4, C4 binding protein (C4bp), C3 and C2 haemolytic activity have been measured in 110 samples from 20 patients with systemic lupus erythematosus (SLE). Significant reductions in comparison to normal levels were found in the mean serum concentrations of C4, C3 and C4bp as well as C2 haemolytic activities. For patients serum concentrations of C4 correlated with C2 haemolytic activities (r = 0.91) and C4bp (r = 0.79); the C2 haemolytic levels correlated with the concentration of C4b (r = 0.72). It is concluded that serum concentrations of the complement components C4 and C2, which are the constituents of the classical pathway C3 convertase, are regulated by C4bp in vivo. Further metabolic studies are required to determine the causes of decreased serum concentrations of C4bp in patients with SLE.

Carrier Proteins↗
PubMed1993

A novel membrane-associated c-type cytochrome, cyt cy, can mediate the photosynthetic growth of Rhodobacter capsulatus and Rhodobacter sphaeroides.

Mutants of Rhodobacter capsulatus lacking the soluble electron carrier cytochrome c2 are able to grow photosynthetically (Ps+), whereas Rhodobacter sphaeroides is unable to do so. To understand this unusual electron transfer pathway the gene required for cyt c2-independent growth of R.capsulatus was sought using chromosomal libraries derived from a cyt c2- mutant of this species to complement a Ps- cyt c2- mutant of R.sphaeroides to Ps+ growth. The complementing 1.2 kbp DNA fragment contained a gene, cycY, encoding a novel membrane-associated c-type cytochrome, cyt cy, based on predicted amino acid sequence, optical difference spectra and SDS-PAGE analysis of chromatophore membranes. The predicted primary sequence of cyt cy is unusual in having two distinct domains, a hydrophobic amino-terminal region and a carboxyl-terminus with strong homology to cytochromes c. A cyt cy- mutant of R.capsulatus remains Ps+ as does the cyt c2- mutant. However, a mutant lacking both cyt c2 and cy is Ps-, and can be complemented to Ps+ by either cyt c2 or cyt cy. These findings demonstrate that each of the cytochromes c2 and cy is essential for photosynthesis only in the absence of the other. Thus, two distinct electron transfer pathways, unrecognized until now, operate during photosynthesis in R.capsulatus under appropriate conditions, one via the soluble cyt c2 and the other via the membrane-associated cyt cy.

Amino Acid Sequence↗
PubMed1977

[Lupus erythematosus and hereditary lack of complement. Review of about one case of C2 deficit (author's transl)].

A 22 year old woman having disseminated discoid L.E. with alopecia, photosensitivity and normal renal function is presented. Speckled FANA type R.N.P. was found; L.E. cells and anti-DNA were not present. Direct IF of involved skin revealed deposits of IgG and C3 forming a band at the dermo-epidermal junction. In normal skin there was speckled epidermal nuclear staining with IgG. The study of the patient's complement revealed a selective defect of the C2 component (0 p.100) with a drop in total complement (6 p. 100). The father probably has a heterozygote deficit of C2 (55 p. 100); the mother, however, is within the normal range (119 p. 100). The HLA investigation of the patient and her immediate family did not demonstrate haplotype A10, B18, DW2 as is frequently seen in cases of L.E. associated with a C2 deficiency. The patient is A1, B18, DW--/A10 (W26), BW15, DW--.

Adult↗
PubMed1982

Quantitative studies of the secretion of complement component C3 by resident, elicited and activated macrophages. Comparison with C2, C4 and lysosomal enzyme release.

To quantitate the secretion of complement component C3 by guinea pig peritoneal macrophages an enzyme-linked immunosorbent assay was developed. C3 secretion was studied in resident, elicited and activated macrophages and compared with release of hemolytically active C2 and C4, as well as the lysosomal enzyme beta-D-2-acetamido-2-deoxyglucosidase. Resident macrophages secreted about 6 ng C3/10(6) cells/h into culture supernatants over a period of 12 h. Corynebacterium parvum-activated cells were found to secrete 3 times that amount at nearly constant rates. There was a stepwise increase in secretion of functional C2 and C4 when comparing resident, elicited and activated macrophages; secretion was 2--4 times higher in activated than in resident cells.

Acetylglucosaminidase↗