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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↗
PubMed1983

Determination of the second component of complement (C2) by electroimmunoassay in sera from patients with systemic lupus erythematosus.

The concentration of C2 was determined by electroimmunoassay in sera from healthy controls, patients with systemic lupus erythematosus (SLE), their relatives and patients with other diseases. Monospecific anti-human C2 serum was obtained by immunizing rabbits with purified human C2 and then absorbing the rabbit serum with inactivated normal human serum that was made insoluble. In addition, it was shown that human C2 could be purified by means of affinity chromatography on anti-C2 antibody coupled Sepharose. The serum concentration of C2 was 37.8 +/- 5.0 (s.d.) micrograms/ml in healthy controls (n = 133). In patients with SLE, the values were below normal in the active phase and were within normal limits in the inactive phase, showing good correlations with other complement parameters such as CH50, C4, C3 and factor B. C2 concentration was well correlated with C2 haemolytic activity in the inactive phase of SLE, but there was no relationship between the two in the active phase. The mean value of C2 concentration in the relatives of patients with SLE showed no significant difference from that in healthy controls. C2 concentration tended to be high in patients with scleroderma, polymyositis, rheumatoid arthritis, Behçet's disease and aortitis syndrome. However, the values were often low in patients with chronic liver diseases, suggesting a decrease of C2 production in the liver.

Chromatography, Affinity↗
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↗
PubMed1994

Alternatively spliced transcripts of the human complement C2 gene.

To investigate the possible presence of alternatively spliced C2 gene transcripts, we amplified mRNA from HepG2 cells by reverse transcription-PCR using primers derived from the 5' and 3' untranslated regions of the C2 mRNA. Cloning of the resulting products revealed the presence of four novel C2 mRNA size variants. Nucleotide sequencing indicated that the variant mRNAs were probably derived through differential splicing of C2 gene transcripts. Specifically, nucleotide sequence deletions in the four variant mRNAs could be attributed to splicing out of: 1) exons 2 and 3; 2) exon 3; 3) exon 17; and 4) exons 6 and 7 and the 5' region of exon 18. The results were confirmed by RNase protection assays using HepG2 mRNA. Inspection of the nucleotide and the deduced amino acid sequences indicated that in the first two variants the alternative splicing did not affect the C2 open reading frame. In the other two variants, frameshifts in exon 18 resulted in termination codons up- or downstream of the authentic termination codon. All four variants C2 mRNAs were capable of encoding truncated C2 proteins, and were detected by reverse transcription-PCR not only in HepG2 cells but also in human liver, U937, and U105-MG cells. The latter analyses indicated the presence of an additional C2 mRNA variant lacking the region encoded by exon 6.

Alternative Splicing↗
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↗
PubMed1982

Contact with specific surfaces stimulates the production of the second component of complement (C2) in human peripheral blood monocytes via a lymphocyte factor.

Whole mononuclear cells plated on surfaces coated with the polymer, poly (2-hydroxyethyl methacrylate) (poly-HEMA) produced significantly less C2 when compared to production by cells on tissue culture plastic dishes. The reduction in C2 production was dependent on the amount of poly-HEMA used to coat the dishes and was not due to nonspecific damage of the cells or effects of the poly-HEMA on the hemolytic activity of C2. T and B lymphocytes, but not monocytes, plated on tissue culture plastic produced a soluble factor that increased the production of C2 in freshly adherent monocytes. Lymphocytes plated on the poly-HEMA surface did not produce this soluble factor, which was termed surface-dependent factor (SDF). Whole mononuclear cells plated on poly-HEMA were able to respond to SDF by increasing C2 production by the same percentage as cells on the tissue culture plastic. This suggested that the primary basis for the decreased production of C2 by monocytes in the whole mononuclear cells plated on the poly-HEMA was decreased production of SDF by the lymphocytes. The effect of the poly-HEMA surface on C2 production was probably related to a generalized alteration in maturation of monocytes into macrophages, for SDF had the same type of effect on beta-glucosaminidase levels in monocytes as seen with C2, except that the magnitude of the effect was less. These studies suggest that interaction of lymphocytes with surfaces may modulate the function of the lymphocytes. In addition, interaction of lymphocytes with surfaces and the production of SDF in vivo may be responsible for enhancing maturation of monocytes in tissues.

B-Lymphocytes↗
PubMed1998

A novel type II complement C2 deficiency allele in an African-American family.

A 9-yr-old African-American male presenting with severe recurrent pyogenic infections was found to have C2 deficiency (C2D). Analysis of his genomic DNA demonstrated that he carried one type I C2D allele associated with the HLA-A25, B18, DR15 haplotype. Screening all 18 exons of the C2 gene by exon-specific PCR/single-strand conformation polymorphism indicated abnormal bands in exons 3, 7, and 6, the latter apparently caused by the 28-bp deletion of the typical type I C2D allele. Nucleotide (nt) sequencing of the PCR-amplified exons 3 and 7 revealed a heterozygous G to A transition at nt 392, causing a C111Y mutation, and a heterozygous G to C transversion at nt 954, causing a E298D mutation and a polymorphic MaeII site. Cys111 is the invariable third half-cystine of the second complement control protein module of C2. Pulse-chase biosynthetic labeling experiments indicated that the C111Y mutant C2 was retained by transfected COS cells and secreted only in minimal amounts. Therefore, this mutation causes a type II C2D. In contrast, the E298D mutation affected neither the secretion of C2 from transfected cells nor its specific hemolytic activity. Analysis of genomic DNA from members of the patient's family indicated that 1) the proband as well as one of his sisters inherited the type I C2D allele from their father and the novel type II C2D allele from their mother; 2) the polymorphic MaeII site caused by the G954C transversion is associated with the type I C2D allele; and 3) the novel C111Y mutation is associated in this family with the haplotype HLA-A28, B58, DR12.

Alleles↗
PubMed1993

Characterization of type I complement C2 deficiency MHC haplotypes. Strong conservation of the complotype/HLA-B-region and absence of disease association due to linked class II genes.

Fourteen individuals with complete C2 deficiency from 11 families and 3 heterozygous C2-deficient individuals from two families were investigated. In all the 24 independent C2-deficient haplotypes, the complotype S042 was present and the majority (21/24) was [HLA-B18,S042,DR2]. All carried the type I C2 deficiency C2 pseudogene with its characteristic 28 bp deletion. All but two haplotypes had 10 AC/GT repeats in the TNF alpha microsatellite polymorphism and all but one of the haplotypes were identical at or near HLA-B as assessed by RFLP using BstEII digestion and two genomic probes, R5A and M20A, located 100 and 38 kb centromeric to HLA-B, respectively. The exceptional haplotype was HLA-B40 with four AC/GT repeats at TNF-alpha. Three of the haplotypes were not DR2 based on generic and sequence-specific oligonucleotide typing. Another four haplotypes showed different DO-variants detected by RFLP analysis using BglIIand Mspl digestion. Thus, the [HLA-B18,S042,DR2] haplotype appears to be more fixed in the region between the complement genes and the HLA-B locus (96%) than in the region between the complement genes and DR (88%) and DO loci (71%). Of the 14 individuals studied, six had SLE or SLE-like syndromes and six had a history of severe infections although two were apparently healthy. Three of the six SLE patients and two individuals with repeated infections were homozygous for [HLA-B18,S042,DR2] and also homozygous for DQB1*0602 and the common DO variant. Thus, MHC class II genes linked to the C2 pseudogene do not appear to determine different clinical consequences of C2 deficiency.

Base Sequence↗