PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Complement C4”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,765 records · Page 98Linked to original sources
PubMed1998

Requirement for the alternative pathway as well as C4 and C2 in complement-dependent hemolysis via the lectin pathway.

Mannan-binding lectin (MBL) is a C1q-like molecule opsonic for several micro-organisms. MBL can activate C4, C2, and later acting complement components in the presence of serine proteases similar to but distinct from C1r and C1s via the lectin pathway of complement activation. We report here that mannan-coated MBL-sensitized erythrocytes are lysed via the lectin pathway in human serum-Mg-EGTA. The surprising occurrence of MBL-initiated lysis in the absence of calcium contrasts with the calcium requirement for C1q-initiated activation of C4 and C2. C2 is required, and lysis is significantly enhanced when indicator cells presensitized with C4 and then coated with mannan (EAC4-M) are used. The alternative pathway also is required, since lysis is lost when either factor D or factor B is removed and is restored upon reconstitution with the purified protein. Even though MBL is a C-type lectin, it is retained on mannan-coated erythrocytes in the absence of calcium. This contrasts with the absence of calcium-independent retention on mannan immobilized on polystyrene plates or beads, and helps explain the MBL-initiated hemolysis in Mg-EGTA. These investigations show that the alternative pathway as well as C4 and C2 of the classical pathway are required for complement-dependent hemolysis via the lectin pathway and provide a method for assay of lectin pathway-mediated complement activity in human serum that should be useful in unraveling the molecular interactions of this pathway.

Calcium↗
PubMedDate not supplied

[Levels of the C 4 component of the complement, lactoferrin and leukocytic thermostabile alpha glycoprotein during the treatment of patients with systemic rheumatic diseases].

The authors studied the dynamics of C4-component of complement (C4), lactoferrin (LF), leukocytic thermostable alpha-glycoprotein (LT alpha G) in the blood serum of 54 patients with rheumatoid arthritis, 32 patients with systemic lupus erythematosus, 8 patients with systemic vasculitis under the effect of hemosorption (HS), enterosorption (ES) and also immunosuppressants (IS). In severe forms of systemic rheumatic diseases the blood serum exhibits a decreased content of C4 but an elevated level of LF and LT alpha G. It has been established that HS is more active than ES or IS, and it influences the mechanisms of humoral immunity. This finds its expression in normalization of C4 level. The favourable clinical effect of HS correlates with a decrease in the level of LF and LT alpha G in the blood serum of patients during treatment.

Adolescent↗
PubMed1996

Complement components C2, C3, and C4 (C4A and C4B) and BF polymorphisms in populations of the Indian subcontinent.

Genetic polymorphisms of the complement components (five loci: C2, C3, C4A, C4B, and BF) have been investigated in the Telugu-speaking Hindu population of Hyderabad, Andhra Pradesh, India, and the Bangali-speaking Muslim population of Dacca, Bangladesh. The available data are compared to understand the genetic variation of complement components in populations of the Indian subcontinent. The C3*F and BF*F alleles show wide frequency variations in different ethnic groups of India. The range of variation in the C3*F allele is intermediate between European whites and southeast Asian populations, whereas the BF*F allele places the Indian frequencies between European whites and African blacks. This is the first population study to investigate the C2 and C4 (C4A and C4B) polymorphisms in two distinct groups of the Indian subcontinent. For the C2 polymorphism only the C2*B variant allele was observed, and its frequency was slightly higher than in European populations. In both populations the C4A and C4B loci were highly polymorphic, with a high frequency of the null alleles C4A*QO and C4B*QO, which may account for the greater susceptibility to certain autoimmune diseases in populations of South Asia.

Bangladesh↗
PubMed1992

Analysis of antibodies and other large glycoproteins in the mass range of 150,000-200,000 Da by electrospray ionization mass spectrometry.

The analytical applicability of electrospray ionization mass spectrometry (ESIMS) to large glycoproteins in the molecular weight (MW) range of 150,000-200,000 was demonstrated. Multiply charged ions (charge state as high as 150+) of several typical macrosized glycoproteins of immunological significance were generated by pneumatically-assisted electrospray (ionspray) and their masses measured on a quadrupole mass spectrometer having a mass-to-charge (m/z) range of 2400. The resolution of the quadrupole instrument was insufficient to resolve the glycocomposition microheterogeneities in the MW range studied. Nevertheless, the average MWs of three immunoglobulin G (IgG) class murine monoclonal antibodies, anti-(human alpha 1-antitrypsin) (148,484 +/- 4), anti-(human alpha 1-acid glycoprotein) (149,599 +/- 12) and anti-(beta-galactosidase) (component I, 150,544 +/- 10, and component II, 151,496 +/- 17), and human alpha 2-macroglobulin monomer (186,100 +/- 100), and human complement component C4 (196,863 +/- 29) were still determined from the fused peak profiles of their constituent glyco components (the errors given reflect the measurement precisions of the simultaneous multichannel MW determinations). The difference between the measured average MW and the unmodified sequence MW was used to assess the degree of post-transitional modification in human alpha 2-macroglobulin (13.6%) and human complement component C4 (5.3%). For the large glycoproteins studied here, glycosylation did not appear to seriously affect the effectiveness of the electrospray ionization; up to 70% of their full charge-retaining capacities were fulfilled under the usual experimental conditions. These results show that ESIMS is capable of providing analytically useful information for macrosized proteins.

Antibodies↗
PubMed2005

[Modification of C3 and C4 levels after the administration of conjugated estrogens plus medroxiprogesterone or raloxifene in postmenopausal women].

OBJECTIVE: To evaluate the effect of conjugated equine estrogens (CEE) plus medroxyprogesterone acetate (MPA) and raloxifene on serum levels of complement C3 and C4 fractions in postmenopausal women. PATIENTS AND METHOD: Twenty healthy postmenopausal women were studied. In all weight, height and body mass index (BMI) were documented. FSH and estradiol levels were measured. They were randomly divided into two groups, according to the treatment they received: group I, CEE 0.625 mg/day plus MPA 2.5 mg/day (n = 7); group II, raloxifene 60 mg/day (n = 13), both treatments were continuous. Serum levels of C3 and C4 complement fractions were measured by immunonephelometry at baseline and six months after start of treatment. Differences among groups of baseline and final C3 and C4 levels were measured with Student's t test for independent and paired samples, respectively. RESULTS: There were no differences among groups in age, weight, height and body mass index, neither in C3 and C4 levels among baseline and final levels when comparing each group separately. CONCLUSIONS: Complement may not intervene significantly in the atherosclerotic inflammatory process in women receiving CEE plus MPA or raloxifene.

Complement C3↗
PubMed1979

[Calcium and magnesium deficiency and C3 fraction of complement].

The third (C3) and fourth (C4) components of complement and C3 proactivator (C3PA) were determined in 55 children with low serum levels of calcium and magnesium and 30 normal children. The concentrations of serum C3, C4 and C3PA were significantly reduced in children with double deficiences of calcium and magnesium. There were significant correlations between calcium and C3 and magnesium and C3PA. The relations between calcium, magnesium and the classical or alternate pathway of complement systems are discussed.

Calcium↗
PubMed1981

Murine binding protein of the fourth component of complement: structural polymorphism and its linkage to the major histocompatibility complex.

The binding protein of the fourth component of complement (C4-BP) is a regulatory protein of the complement system with specific affinity for the fourth component. This paper describes a structural polymorphism of murine C4-BP and its linkage to the major histocompatibility complex of the mouse (H-2). After isoelectric focusing of whole mouse plasma in low-endosmosis agarose, C4-BP was demonstrated as a single precipitin band by overlaying monospecific antiserum on the agarose gel. Two C4-BP patterns were distinguished among many strains of mice on the basis of isoelectric point--C4-BP a type, which has a pH range of 6.5-7.0 (exemplified by B10.BR and B10.AKM), and C4-BP b type, which has a pH range of 6.3-6.6 (exemplified by B10 and B10.M). Genetic crosses between two strains bearing distinct C4-BP types demonstrate a C4-BP pattern representative of both types. A linkage study was carried out in which progeny of two backcross combinations--[(B10 X B10.BR)F1 X B10.BR] and [(B10.AKM X B10)F1 X B10.AKM]--were phenotyped for C4-BP type and serum fourth-component level. Results were obtained suggesting that C4-BP patterns are inherited by a single codominant locus (C4-Bp) linked to the H-2 complex. The recombination frequency between the C4-Bp locus and the S region was 0.017. By phenotyping appropriate intra-H-2 recombinants of three different backgrounds (B10, A, and HT), this locus was assigned to the right of the H-2D region.

Animals↗
PubMed1994

C4 gene polymorphism in primates: evolution, generation, and Chido and Rodgers antigenicity.

Eleven new C4d genomic primate sequences of the fourth complement factor (C4) have been obtained. Seven of them belong to five species not yet explored for this gene: Pan paniscus (pygmy chimpanzee), Cercopithecus aethiops (green monkey), Macaca mulatta (rhesus monkey), Macaca fascicularis (cynomolgus), and Saguinus oedipus (cotton top tamarin). The New World monkeys (tamarins, four individuals) sequenced for C4 have a single C4d sequence only, which shows a B isotypic specificity and a Rodgers 3 (Rg3), Chido 1 (Ch1) antigenicity. Rg3 and Ch1 could thus be the oldest Rg/Ch specificity (at least 50 million years old) and Rg1, Rg2, Ch3, and Ch6 could be more recent human-specific antigens. Mechanisms of C4d polymorphism generation were analyzed by compiling all the presently available sequences. Examples of both point mutations and crossing-over events among C4d primate sequences could be detected. The problem of a possible trans-species inheritance of C4d polymorphism was addressed and two apparently contradicting dendrograms were obtained. One of them, constructed by using both exon and intron sequences, does not support trans-species evolution, but supports the proposed theory of extensive homogenization of the C4 genes occurring within each species, because alleles from each primate species cluster together. Another completely different dendrogram, obtained by using exon sequences only, suggests the existence of trans-species evolution for C4d polymorphism, because alleles belonging to different species cluster together in a way similar to that found for HLA class I or II alleles. However, orangutan sequences group together in both kinds of C4d sequence dendrograms and seem to have arisen from an ancestor different from that of chimpanzee, gorilla and man C4d sequences. Finally, further data have been obtained that support trans-species conservation of A-ness and B-ness and the existence of trans-specifically conserved allelic motifs, both in intronic and exonic sequences.

Amino Acid Sequence↗
PubMed1992

Isolation of a hagfish gene that encodes a complement component.

It has been widely accepted that cyclostomes are the most primitive vertebrates extant with the ability to produce antibodies. We isolated cDNA clones that encode a putative 'antibody' from one of the cyclostomes, Eptatretus burgeri. The amino acid sequence predicted from the nucleotide sequences of the cDNA clones indicated that this gene does actually encode the proteins isolated as hagfish 'antibodies' by various investigators. However, these proteins are not similar to mammalian immunoglobulins but have some characteristics common to complements C3, C4 and C5 in higher vertebrates. We discuss the relationships of the isolated gene for hagfish complement with the mammalian genes for complements C3, C4 and C5. We also discuss the possibility of the presence of antibodies in cyclostomes.

Amino Acid Sequence↗
PubMed1991

Complement function and the synthesis of lung surfactant may be a regulation which preterm infants have in common.

The levels of CH50, the complement components, C1q, C4, and C3, C3 degradation fragments, and factor B were determined in the cord blood of 128 newborn infants. The levels of C3, C4, and C3d3 (an index of chronic in vivo complement activation) were clearly lower in the 28 infants with respiratory distress syndrome (RDS) than in the infants with other lung diseases or with normal lungs. CH50 and factor B levels were also low in RDS. Levels of C1q and other serum components in RDS infants were similar to the average levels in other infants without RDS at a corresponding gestational age. Lung surfactant is synthesized in alveolar type 2 cells, in which the complement components C4, C3, and factor B, but not C1q, have been reported to be synthesized. It seems possible that common factors regulate the synthesis of some complement components and surfactant.

Complement C1q↗
PubMed1993

Genetic study on HLA class II and class III region in the disease associated with IgA nephropathy.

Increased frequency of C4 gene deletions in IgA nephropathy and Henoch-Schönlein purpura nephritis. To determine the frequency of complement 4 (C4) deficiency among the patients with IgA nephropathy (IgAN) and Henoch-Schönlein purpura nephritis (HSPN), C4 and factor B protein allotypes and the DNA restriction fragment length polymorphism (RFLP) of C4, steroid 21-hydroxylase (21OHase), HLA DQ beta and DR beta chain genes were studied. Genomic DNA from 32 patients with IgAN, 24 patients with HSPN and 143 controls was digested with restriction enzyme TaqI or BamHI and subjected to Southern analysis. The frequency of C4 gene deletions was significantly increased in the patients (16.1 vs. 2.8%, p = 0.002). The serum C4 concentration in patients with C4 gene deletion was significantly lower than in patients without gene deletion (11.4 +/- 2.4 vs. 19.7 +/- 5.2 mg/dl, p = 0.001). DNA-RFLP typing of DQB/BamHI and DRB/TaqI showed increased frequency of 10.26 kb of D-DQw4/8/9 (87.5 vs. 64.5%, p = 0.004) and 5.22 kb of D-DR4 (66.1 vs. 41.7%, p = 0.03) among the patients. Segregation analysis showed that the association of the D-DQw4/8/9 and D-DR4 with the diseases was not responsible for the increased frequency of C4 gene deletion in the patients. The decreased concentration of C4 in sera in C4 gene-deleted patients might be directly involved in the pathogenesis of IgAN and HSPN.

Child↗
PubMed1981

[Comparison of consumption kinetics of the C4 and C2 components of complement by immune complexes "in vitro" (author's transl)].

We study the consumption kinetic of the fourth and second component of complement by the C1 esterase in different systems with EA or EAC1 and fresh NHS, or functionally purified C4 and C2 preparations. The results show that the two kinetics are similar with a comparable decrease in both C4 and C2 activities till 90 seconds (the mean residual values are from 21 to 34% at this time). The results show moreover that the consumption of the C2 component requires necessarily the presence of the C4 component. The C4 reaction kinetic compared with the C2 "in vitro" one refutes the hypothesis of a greater sensitivity of the C4 component compared with the C2, for the enzymatic action of the C1 esterase. So, a discrepancy in the reaction speed cannot be evoked in order to explain the obvious C4 depression in the consumption hypocomplementemia, and different hypothesis have to be investigated, such as, for instance, a lower synthesis rate of the C4 component compared with the C2 one.

Animals↗