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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↗
PubMed1995

Upstream sequence elements enhance poly(A) site efficiency of the C2 complement gene and are phylogenetically conserved.

Poly(A) signals of mammalian pre-mRNA have been defined as an AAUAAA sequence 10-30 nt upstream of the cleavage/poly(A) site followed by a GU/U-rich element immediately downstream. However, a number of viral poly(A) signals have been shown to possess additional signals upstream of AAUAAA that increase poly(A) site efficiency. We describe the first non-viral example of such an upstream sequence element (USE) for the poly(A) site of the human C2 complement gene. As this gene is very closely spaced to the related Factor B gene [the C2 poly(A) site is only 421 bp from the transcription start site of Factor B] we have isolated this same intergenic sequence from four other mammals (mouse, cat, rabbit and cow). We show that the USE of the C2 poly(A) site is highly conserved between these five different mammals. Furthermore, extensive mutagenesis of the human USE indicates that most of the 53 nt sequence is required for full activity. The human C2 poly(A) site does not possess any obvious downstream GU/U-rich sequences, although sequences immediately 3' to AAUAAA as well as 13 nt of sequence following the cleavage site are both required for full activity. Interestingly the other mammalian C2 poly(A) sites do possess significant downstream GU/U-rich sequences. Finally we show that all five mammalian C2 poly(A) signals are immediately followed by conserved signals for transcriptional termination, consistent with the close proximity of the downstream Factor B gene.

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↗
PubMed1983

Lymphokine and phorbol (PMA) regulation of complement (C2) synthesis using U937.

Human monocytes synthesize large amounts of the second complement component (C2) after incubation with a T-lymphocyte product called monocyte complement stimulator (MCS). The human monocyte-like cell line, U937, also synthesizes C2 and can be stimulated to increase this synthesis by lymphokine-rich culture supernates. Additionally, phorbol myristate acetate (PMA), an agent which induces maturational changes in other macrophage-like cell lines, also stimulates C2 synthesis by U937 cells. Lymphokine and PMA stimulation of C2 secretion by U937 are both reversibly inhibitable by cycloheximide. At optimal concentrations for stimulation of C2 synthesis, PMA inhibits [3H]thymidine incorporation by U937 indicating that increased C2 is not due to increased numbers of U937 cells.

Cell Division↗
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↗
PubMedDate not supplied

Complement C2, C3, C4 and factor B allele distribution in the Gipsy population in Hungary.

Allotype frequencies of four complement proteins (C3, C2, factor B, and C4) were tested in 150 healthy Hungarian and 126 healthy Gipsy individuals living in Hungary. We observed significant differences between the two ethnic groups in the incidence of C3*F, Bf*F, C4A*Q0, C4A*3, C4B*1 and C4B*2 allotypes. Bf*F occurred more frequently among Gipsies, while frequencies for the other three allotypes was lower in this group than in Hungarians. The similarities in the allotype frequencies of C3 and Bf among Gipsy and Gaddis (India) populations supports the Indian origin of the former ethnic group.

Adult↗
PubMed1985

HLA, complement C2, C4, properdin factor B and glyoxalase types in South Indian diabetics.

A series of diabetic patients from 3 centres in South India have been tested for HLA A, HLA B, BF, C2, C4A, C4B and GLO types. For insulin-dependent diabetes mellitus (IDDM) patients there was a significant increase in HLA B8, of BF F and decrease of C4 A6. No significant variation in HLA, BF, C2 or GLO frequencies was found in non-insulin-dependent diabetes mellitus (NIDDM) patients, but there was a significant decrease in C4B 1 and an increase in C4B 2. The HLA and BF association in South Indian IDDM patients is very different from that reported previously in North India.

Adolescent↗
PubMed1986

Studies of HLA, factor B (Bf), complement C2 and C4 haplotypes in type 1 diabetic and control families from northern Sweden.

The HLA-A,-B,-C,-DR antigens and the complement factors C2, C4 and Bf were determined in 30 insulin-dependent diabetes mellitus (IDDM) patients and 30 healthy controls from northern Sweden. Family studies allowed the deduction of extended haplotypes in the HLA and complement systems. Phenotype studies revealed significant associations between IDDM and HLA-DR4 (p less than 0.001), HLA-DR3 (p less than 0.05), HLA-DR3/4 (p less than 0.025), C4-B3 (p less than 0.001) and Bf-S (p less than 0.025). Haplotype studies showed that the extended haplotype [HLA-B15, C2-1, C4-A3B3, Bf-S, HLA-DR4] had a particularly strong association to IDDM. This haplotype was found in 10 out of 30 IDDM probands but in none of 30 control children and accounts for practically all the C4-B3 allotypes among the 30 IDDM probands. The C4-B3 gene therefore seems to be a valuable marker for IDDM. No haplotype containing HLA-DR3 was increased in frequency among the IDDM probands. The extended haplotype [HLA-B7, C2-1, C4-A3B1, Bf-S, HLA-DR2] present among the controls was absent in the IDDM probands. The frequency of the extended haplotype [HLA-B15, C2-1, C4-A3B3, Bf-S, HLA-DR4] was increased also among the parents to the IDDM probands compared to those of the control parents, whereas the frequency of [HLA-B7, C2-1, C4-A3B1, Bf-S, HLA-DR2] was decreased. The extended haplotype [HLA-B8, C2-1, C4-B1, Bf-S, HLA-DR3] was more common among the males (p less than 0.05) compared to the females in the total material. The family analysis showed that 3 out of 5 affected sibs shared both haplotypes with their IDDM proband. This was the case for only 3 out of 35 unaffected sibs.

Adolescent↗
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↗