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PubMed1979

Hereditary complement (C2) deficiency with discoid lupus erythematosus and idiopathic atrophoderma.

A family with hereditary deficiency of the second component of complement was studied. Three siblings were homozygous for C2 deficiency and two of them had associated skin diseases. One sister presented with idiopathic atrophoderma and the other had clinical and pathological manifestations of discoid lupus erythematosus. This is the first description of an association between idiopathic atrophoderma and C2 deficient state.

Adolescent↗
PubMed1979

Polymorphism of the second component of human complement (C2). Observation of the rare phenotype (C2 2 (= C2 B) and data on the localization of the C2 locus in the HLA region.

The polymorphism of the second component of human complement was studied by means of isoelectric focusing in polyacrylamide gels with subsequent complement-dependent lysis of sensitized sheep erythrocytes in an agarose overlay containing C2-deficient or normal human serum. In a material of 289 unrelated individuals the following gene frequencies were observed: C21=0.965 and C22=0.035. The rare phenotype C2 2 (=C2 B) could be seen once in a child of a C2 1--2 heterozygous mother. The investigation of the C2/HLA relationship revealed a very close linkage: Among 62 informative meiotic divisions one recombination between HLA-B and C2 was found (i.e. 1.61%); in addition, C2(2) was significantly associated with HLA-B15 and -Cw3. In a family with an HLA-B/D(DR) crossover C2 segregated together with HLA-D(DR). This supports the assumption of a C2 structural locus outside HLA-B, probably near HLA-D(DR).

Alleles↗
PubMed1978

Genetic polymorphism of the second component of human complement (C2): presentation of a modified typing technique and data on C2 phenotype distribution, linkage genetics, and haplotype associations a Norwegian family material.

Proteins were separated by prolonged isoelectric focusing in polyacrylamide gels, whereupon C2 bands were detected by a specific hemolytic assay. This was performed by treating the gel with iodine to increase C2 activity, and then developing C2 bands with an agarose gel overlay containing sensitized sheep cells and diluted human serum as a complement source deficient in functional C2. The gene frequencies observed in a material of 122 unrelated adults were: C2(1): 0.97 and C2(2): 0.03. C2 linkage relations and C2 haplotype associations have been examined a family material. It is concluded that C2 is very closely linked to HLA loci.

Adult↗
PubMed1989

[Genetic polymorphism of the second component of human complement (C2) in the Han Nationality in Wuhan district of China].

A total number of 231 unrelated Chinese (Han Nationality) were investigated for C2 polymorphism by hemolytic overlay technique after polyacrylamide gel isoelectric focusing on plasmas. The following phenotype distributions were observed: C2C, 216; C2BC, 9; C2AC, 5; and C2A, 1. The gene frequencies calculated from these phenotypes were as follows: C2*A, 0.015; C2*B, 0.019; C2*C, 0.965. The C2 phenotypic frequency distributions were in agreement with those expected from Hardy-Weinberg equilibrium.

China↗
PubMed1992

A variable number of tandem repeats locus within the human complement C2 gene is associated with a retroposon derived from a human endogenous retrovirus.

We have previously described multiallelic restriction fragment length polymorphisms of the C2 gene, suggesting the presence of a variable number of tandem repeats (VNTR) locus. We report here the cloning and sequencing of the polymorphic fragments from the two most common alleles of the gene, a and b. The results confirm the presence of a VNTR locus consisting of a nucleotide sequence, 41 bp in average length, repeated tandemly 23 and 17 times in alleles a and b, respectively. The difference in the number of repeats between the two alleles is due to the deletion/insertion of two noncontiguous segments, 143 and 118 bp long, of allele a, and of a 40-bp segment of allele b. The VNTR region is associated with a SINE (short interspersed sequence)-type retroposon, SINE-R.C2, located within the third intron of the C2 gene. SINE-R.C2 is a member of a previously described large retroposon family of the human genome, apparently derived from the human endogenous retrovirus, (HERV) K10, which is homologous to the mouse mammary tumor virus.

Alleles↗
PubMed1986

Human complement component C2: production and characterization of polyclonal and monoclonal antibodies against C2.

Rabbit antibodies to human complement component C2 were produced by immunization of rabbits with precipitates from line immunoelectrophoresis, and the antibodies were used to monitor a classical chromatographic purification of C2 and for affinity purification of C2. Twelve monoclonal antibodies with specificity for human complement component C2 were produced by fusion of myeloma cells with spleen cells from mice immunized with the affinity purified C2. The specificity of the monoclonal antibodies was confirmed by their reaction with antigen-antibody precipitates where C2 was the antigen, and by their specific reaction with C2 after separation in SDS-PAGE followed by immunoblotting. The affinity of the monoclonal antibodies varied as demonstrated by the titration curves in ELISA. The antibodies will be of importance for immunospecific purification of human C2 and C2 fragments, for specific depletion of C2 from human serum, and for quantification of C2 for clinical purposes.

Animals↗
PubMed1990

Allelic associations of multiple RFLPs of the gene encoding complement protein C2.

The gene for the second component of complement, C2, maps within the class III region of the major histocompatibility complex (MHC). Many human diseases have been reported to be associated with MHC alleles, haplotypes, or extended haplotypes, but in most cases additional polymorphic markers are needed for the eventual localization of the genes responsible for these diseases. In this study, nine C2 haplotypes for four restriction-site polymorphisms, detected by SstI, BamHI, and TaqI, were defined among 143 unrelated individuals. Two of these polymorphisms are multiallelic and map near the 5' end of the C2 gene. The extensive allelic variation of the C2 gene may prove of value in studies of diseases associated with the MHC.

Alleles↗
PubMed1986

Primary structure of human complement component C2. Homology to two unrelated protein families.

The primary structure of the second component of human complement (C2) was determined by cDNA cloning and sequence analysis. C2 has 39% identity with the functionally analogous protein Factor B. The C-terminal half of C2a is homologous to the catalytic domains of other serine proteinases. C2b contains three direct repeats of approx. 60 amino acid residues. They are homologous to repeats in Factor B, C4b-binding protein and Factor H, suggesting a functional significance of the repeat in C4b and C3b binding. The repeats are also found in the non-complement proteins beta 2-glycoprotein I and interleukin-2 receptor, and this repeat family may be widespread.

Amino Acid Sequence↗
PubMed1985

gamma-Interferon increases expression of class III complement genes C2 and factor B in human monocytes and in murine fibroblasts transfected with human C2 and factor B genes.

gamma-Interferon (IFN-gamma) is a well characterized lymphokine known to regulate many mononuclear phagocyte functions, including expression of class I and class II major histocompatibility complex genes. The second component of complement (C2) and factor B are major histocompatibility complex class III gene products synthesized in mononuclear phagocytes. Recombinant IFN-gamma increased the synthesis of C2 and factor B in primary cultures of human mononuclear phagocytes and in murine fibroblasts transfected with cosmid DNA bearing the human C2 and factor B genes. In both cell types the increases in C2 and factor B protein synthesis were detected at concentrations of IFN-gamma less than 1 unit/ml and the regulation of each was pretranslational. The IFN-gamma-induced increases in C2 and factor B mRNA did not require new protein synthesis. In primary cultures of human monocytes, the kinetics of induction of C2 and factor B synthesis differed, but in the transfected L-cells the kinetics were similar, suggesting differences in transduction of the IFN-gamma signal, transcriptional, and/or post-transcriptional events in the two cell types. The small size of the factor B 5' flanking region, which is bounded by the 3' terminus of the IFN-gamma-regulated C2 gene, provides a well defined region to probe the structural basis for IFN-gamma regulation of gene expression.

Animals↗
PubMed1989

Measurement of complement proteins C2 and B in systemic lupus erythematosus and septic shock.

We developed sensitive radioassays to quantitate the homologous complement proteins C2 and B, in intact form, in sera from patients with diseases associated with hypocomplementemia. In a study of systemic lupus erythematosus (SLE) patients, we found a subset of patients (6/40) with low C2 concentrations, though overall, C2 concentration was not related to disease activity. Protein B concentration was increased in 23/40 SLE patients, apparently not due to a generalized acute phase response. Among patients with both gram-negative and gram-positive septic shock, C2 and B concentrations were low in a subset of patients with pre-existing cirrhosis, suggesting hepatic hyposynthesis of these proteins may be important in their prognosis and predisposition to severe infections.

Biomarkers↗
PubMed1992

Production and interferon-gamma-mediated regulation of complement component C2 and factors B and D by the astroglioma cell line U105-MG.

In this paper, we demonstrate the synthesis of the complement component C2 and factors B and D by the human astroglioma cell line U105-MG. All three components were structurally and antigenically similar to their serum counterparts, as determined by biosynthetic labelling studies or Western blot analysis. Northern blot analysis demonstrated that the mRNAs of all three components had the same apparent sizes as the equivalent mRNAs from hepatocyte and monocyte cell lines. Interestingly, U105-MG cells produce two C2 transcripts with sizes of approximately 2.8 and 2.3 kb. Interferon-gamma (IFN-gamma) enhanced the expression of C2 and factor B mRNA and protein in a dose- and time-dependent fashion, while factor D expression was refractory to IFN-gamma. IFN-gamma appeared to predominantly enhance the expression of the large (2.8 kb) C2 transcript. Kinetic studies demonstrated peak C2 and factor B expression in 48 h in response to IFN-gamma, similar to the acute-phase response of factor B in serum. These data are the first to demonstrate the synthesis of C2 and factor D by astroglioma cells. Combined with previous reports documenting the synthesis of C3 by astrocytes, our data suggest that endogenous synthesis of complement proteins, and particularly of alternative pathway activation components (C3, factors B and D), may play an important role in host defence in the central nervous system.

Astrocytoma↗
PubMed1979

Limited proteolysis of complement components C2 and factor B. Structural analogy and limited sequence homology.

A method is described for the simultaneous purification of milligram quantities of complement components C2 and Factor B. Both products are homogeneous by the criteria of polyacrylamide-gel electrophoresis and N-terminal sequence analysis. Component C2 is cleaved by serine proteinase C1s at an X-Lys bond to give fragment C2a (approx. mol.wt. 74000) and fragment C2b (approx. mol.wt. 34000). The two fragments can be separated by gel filtration without the need for reducing or denaturing agents. Fragment C2b represents the N-terminal end of the molecule. Similar results were seen on cleavage of Factor B by Factor D in the presence of component C3. Again two non-covalently linked fragments are formed. The smaller, fragment Ba (approx. mol.wt. 36,000),) has threonine as the N-terminal residue, as does Factor B; the larger, fragment Bb (approx. mol. wt. 58000), has lysine as the N-terminal residue. A similar cleavage pattern is obtained on limited proteolysis of Factor B by trypsin, suggesting an Arg-Lys-or Lys-Lys bond at the point of cleavage. Although component C2 and Factor B show no apparent N-terminal sequence homology, a limited degree of sequence homology is seen around the sites of proteolytic cleavage.

Amino Acid Sequence↗