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At least 19 recordsLinked to original sources
PubMed1991

A simple radial immunohemolysis assay for the measurement of functional complement C2 activity.

1. This study describes a simple radial immunohemolysis method for determining the hemolytic activity of the second component of complement (C2) in human serum. The assay is based on the recovery of hemolytic activity of normal serum which has been pretreated to inactivate endogenous C2 and then mixed with test serum containing an unknown amount of C2. 2. The pretreated serum, designated R2 reagent, is obtained by heating normal human sera under carefully standardized conditions of temperature, time, volume and type of test tube. 3. R2 reagent is incorporated into agarose together with hemolysin-sensitized erythrocytes, and spread on a plate. The test serum is placed in wells cut in the agarose and, after appropriate incubation, the diameters of the hemolytic areas are measured. The area of hemolysis is directly proportional to the logarithm of the serum concentration. As a standard for C2 functional activity, dilutions of a pool of normal sera are tested on the same plate. 4. The method is specific for C2 and can detect as little as 20% of the C2 in normal serum (about 6 micrograms C2 protein/ml). The error in reproducibility is about 3% of the mean. In normal serum, the lower confidence limit of the distribution of the C2 values (based on a sample of 80 individuals) corresponded to 70% of undiluted serum. 5. This method is suitable for use in clinical laboratories since it is simple, rapid, quantitative and inexpensive, and does not require special equipment.

Adolescent↗
PubMed1975

Hereditary complement (C2) deficiency with dermatomyositis.

A 60 year old white man in previous good health presented with a 6 month history of progressive muscle weakness. Clinical and laboratory findings were typical of dermatomyositis. Muscle biopsy confirmed the presence of inflammatory myopathy; deposits of immunoglobulin G (IgG), immunoglobulin M (IgM) or third component of complement (C3) were not detected by immunofluorescence. No evidence was found for an associated neoplasm. An unexpected finding was the total absence of serum hemolytic complement activity. Further investigation revealed that the complement defect was attributable to a selective and total absence of the second component of complement (C2), as determined by both functional and immunoprecipitin assays. Family studies indicated that the defect was inherited in an autosomal recessive manner, as has been observed in the previously reported C2-deficient kindreds. This case demonstrates that typical muscle lesions of dermatomyositis can occur in the presence of a complement defect which would preclude activation of the classic (C1-C4-C2) complement pathway. The case is of further interest as one of a series of recently reported associations of rheumatic diseases with hereditary complement deficiencies. Study of the functional properties of the propositus' C2-deficient serum demonstrated normal generation of chemotactic activity in the presence of endotoxin or aggregated IgG, and normal or near normal bactericidal activity against Salmonella typhi O 901 and Hemophilus influenzae, type b. These findings emphasize the importance of the alternate (properdin) pathway of complement activiation in these functions.

Biopsy↗
PubMed1977

Structural heterogeneity of C2 Complement protein and its genetic variants in man: a new polymorphism of the HLA region.

A zymogram method, following thin-layer isoelectric focusing in a polyacrylamide gel, allows resolution of the lytic activity of serum C2 complement protein in a spectrum of molecular forms. This spectrum is characteristic in each of the species studied (man, rhesus monkey, guinea pig, and hamster). Moreover, two different alternative patterns are observed in man: each of the six major lytic bands characteristic of the most common pattern (herein designated C2(1) is duplicated in the least common pattern (C2(2-1), with an additional band displaced cathodally by not more than 0.04 pH unit. Distribution of phenotypes C2(1) and C2(2-1) in a Caucasion population is in agreement with the hypothesis that they are controlled by two alleles, C2(1) and C2(2), with frequencies 0.96 and 0.04 +/- 0.01. Segregation studies show that the two alleles are codominant and identify a locus in the HLA region. No recombinants with HLA-B were detected among 27 informative meioses, generating a cumulative lod score of 6.321 at equals 0. These findings suggest that the individuals with the C2-deficient trait might be interpreted as homozygotes for a third and rarest amorph C2 degrees of the same locus.

Animals↗
PubMed1992

Type I human complement C2 deficiency. A 28-base pair gene deletion causes skipping of exon 6 during RNA splicing.

Two variants of a genetic deficiency of complement protein C2 (C2D) have been previously identified. No C2 protein translation is detected in type I deficiency, while type II deficiency is characterized by a selective block in C2 secretion. Type I C2 deficiency was described in a family in which the C2 null allele (C2Q0) is associated with the major histocompatibility haplotype/complotype HLA-A25,B18,C2Q0,BfS,C4A4, C4B2,Drw2; this extended haplotype occurs in over 90% of C2-deficient individuals (common complotype/haplotype). To determine the molecular basis of type I C2 deficiency, the C2 gene and cDNA were characterized from a homozygous type I C2-deficient individual with the common associated haplotype/complotype. We found a 28-base pair deletion in the type I C2Q0 gene, beginning 9 base pairs upstream of the 3'-end of exon 6, that generates a C2 transcript with a complete deletion of exon 6 (134 base pair) and a premature termination codon. In studies of eight kindred, the 28-base pair deletion was observed in all C2Q0 alleles associated with the common type I deficient complotype/haplotype; this deletion was not present in normal C2 nor in type II C2-deficient genes. These data demonstrate that: 1) type I human complement C2 deficiency is caused by a 28-base pair genomic deletion that causes skipping of exon 6 during RNA splicing, resulting in generation of a premature termination codon, 2) the 28-base pair deletion in the type I C2Q0 gene is strongly associated with the HLA haplotype/complotype A25,B18,C2Q0,BfS,C4A4,C4B2,Drw2, suggesting that all C2-deficient individuals with this haplotype/complotype will harbor the 28-base pair C2 gene deletion, and 3) type II C2 deficiency is caused by a different, as yet uncharacterized, molecular genetic defect.

Amino Acid Sequence↗
PubMed1975

Deficiency of the second component of complement (C2) with chronic vasculitis.

A patient had complete deficiency of the second component of complement associated with chronic vasculitis and increased susceptibility to infection. We discuss here results of the complement profile, histocompatibility typing, and studies of the functional properties of patient plasma or serum in chemotaxis and opsonization in relation to the disease entity and host susceptibility to infection.

Adult↗
PubMed1976

C3 metabolism in a patient with deficiency of the second component of complement (C2) and discoid lupus erythematosus.

A patient with a hereditary deficiency of the second component of complement and discoid lupus erythematosus with features of systemic lupus erythematosus was studied. The propositus had a 9-year history of rash and arthralgia. Transient renal disease had completely resolved; there was a history of seizures. Examination of his serum disclosed antinuclear antibodies but no total haemolytic complement activity. C2 was absent. Serum concentrations of C1s, C3, C5 and C9 were elevated; other complement components were present in normal concentration, including C3 pro-activator. The patient's C3 pro-activator was electrophoretically converted by inulin and four of five lipopolysaccharides, but was poorly converted by aggregated human IgG. Two separate turnover studies with radiolabelled C3 showed fractional catabolic rates of 3-03 and 2-48% of the remaining plasma pool/hr (range of three normals: 1-62-2-18%/hr); and estimated C3 synthetic rates of 2-74 and 2-31 mg/kg/hr (range of three normals: 0-89-1-40 mg/kg/hr). Serum complement profiles of the patient's family demonstrated that the C2 deficiency was inherited as an autosomal codominant. One sibling, homozygous for C2 deficiency, and three other siblings, both parents and one daughter, all heterozygous for C2 deficiency, are in good health. Immunofluorescent studies of the patient's diseased skin exhibited substantial deposits of IgG, IgM, C1q, and C4 but not of later acting complement components, properdin, or C3 proactivator. These studies do not support the notion that inflammation in C3-deficient individuals with lupus erythematosus is mediated by the alternative complement pathway.

Adult↗
PubMed1978

The second component of complement (C2) as an index of hereditary angioneurotic edema.

Measurements of C2 hemolytic activity were performed in the sera of 13 patients with Hereditary Angioneurotic Edema. Prior to treatment, C2 values correlated with the severity of the disease in each patient. During androgen therapy with Danazol, C2 measurements reflected the clinical benefit of the drug more accurately than C4 levels, thus explaining the effectiveness of low drug doses. This study also suggests that breakdown products of C2 may play an essential role in the pathogenesis of the edema.

Angioedema↗
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↗
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↗