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PubMed1984

C4 polymorphism: use of a monoclonal antibody to distinguish C4A and C4B locus products.

A monoclonal antibody reactive against C4B locus products was used in a passive immunoblotting technique to distinguish C4B from C4A electrophoretic variants. The technique is simple and has the advantage of being able to distinguish clearly those C4B variants which may be either difficult to define by conventional hemolytic assay alone or which would normally be designated as C4B products on account of their lack of hemolytic function. Patterns detected by immunoblotting can be compared directly with patterns obtained by immunofixation with anti-C4 from the same gel.

Alleles↗

PubMed1995

Covalently-bound human C4b dimers consisting of C4B isotype show higher hemolytic activity than those of C4A in the C3-bypass complement pathway.

The ability to form a covalent dimer of human C4b was investigated with purified isotypes C4A and C4B, and antibody-sensitized liposomes supplemented with C1. In this system, no C4A or C4B formed a complex with the antibody or C1. Whereas both C4A and C4B isotypes formed dimers to a similar extent, C4B formed an ester-linked dimer and C4A an amide-linked dimer. Both of these dimers served as a subunit for the C3-bypass pathway C5 convertase, since liposomes bearing Ab, C1 and a dimer of C4A or C4B, allowed the formation of C5 convertase by the addition of C2. The degree of complement-mediated liposome lysis however, was observed to be 2-3 times higher in the C4B-bearing particles than in those bearing C4A. These results indicate that the second C4b-binding site on the first C4b is different between C4A and C4B, and that in the C3-bypass pathway, C4B has a higher degree of hemolytic activity than C4A, as in the conventional classical complement pathway.

Biopolymers↗

PubMed1991

The genomic structure of two ancestral haplotypes carrying C4A duplications.

Two major histocompatibility complex (MHC) ancestral haplotypes (AH) HLA A24, Bw52, C2C, BfS, C4A3+2, C4BQO, DRw15, DQw6 (52.1) and HLA A24, Cw7, B7, C2C, BfS, C4A3+3, C4B1, DR1, DQw5 (7.2), which occur with the haplotype frequencies of approximately 10% and 4% respectively in the Japanese population, carry duplicated C4A alleles by C4 allotyping. Southern blot analysis with Taq I indicated that the 52.1 AH has two C4 genes defined by 7.0 kilobase (kb) and 6.0 kb C4 hybridizing fragments but both encode C4A allotypes, being C4A3 and C4A2 respectively. The 7.2 AH carries two C4A3 and one C4B1 alleles and restriction length polymorphism (RFLP) analysis with Taq I showed that 6.0 kb and 7.0 kb fragments are in the proportion of 2:1. By pulsed field gel electrophoresis (PFGE) analysis, the lengths of the Pvul fragments carrying C4 and Cyp21 genes were approximately 390 kb for 52.1 and 440 kb to 7.2. The results indicate that the RFLP markers do not correlate with C4 isotype (A or B) or allotype and that the C4 gene copy number is a function of the number of genomic blocks containing C4 and Cyp21.

Alleles↗

PubMed1992

Polymorphisms of HLA class III genes in allergic contact dermatitis.

HLA class III polymorphisms (BF, C4A, C4B) were studied in 55 patients of different age and sex suffering from allergic contact dermatitis, with sensitization to different substances. In the overall group of patients no significant correlation between the disease and HLA markers was found. BF F allele was present in 34% and BS S in 64% of patients suffering from allergic contact dermatitis to nickel only versus 16.45% (relative risk, RR = 2.61) and 80.76% (RR = 0.42), respectively, of the control population. The BF FB subtype frequency was 23.91% versus 7.57% in the control samples (RR = 3.88). We thus hypothesize that this polymorphic serum protein might be involved in the pathogenesis of allergic contact dermatitis to nickel.

Adolescent↗

PubMed1981

Comparative study on biological activities of various anaphylatoxins (C4a, C3a, C5a). Investigations on their ability to induce platelet secretion.

Several anaphylatoxic substances (human C3a, guinea pig C3a, human C4a, guinea pig C5a, and a synthetic C3a-related hexapeptide) were compared with regard to their ability to induce secretion of [3H] serotonin from guinea pig platelets. Functional identity of the C3a preparations, C4a, and the hexapeptide was demonstrated by the phenomenon of crossed desensitization. Whereas C3a of human and guinea pig origin proved to be qualitatively and quantitatively identical, C4a expressed only 3% of the activity of the C3 fragments on a molar basis. Investigations with goat anti-guinea pig C3a demonstrate that human and guinea pig C3a possess one antigenic determinant in common; however, this determinant is not the C-terminal amino acid sequence. Addition of the anaphylatoxins with low doses of thrombin led to a potentiation of [3H] serotonin release from the platelets. Under these conditions C3a concentrations of 1.5 X 10(-10) mumol/liter (65 pg of C3a) could be detected. Thus the platelet system represents the most sensitive in vitro assay known for evaluation of biological activity of the C3a anaphylatoxins.

Anaphylatoxins↗

PubMed1992

[Fundamental and clinical studies of homologous immunoglobulin-free priming in cardiopulmonary bypass, with special reference to anaphylatoxin production].

In in-vitro study, human immunoglobulin (Ig) denatured by O2 bubbling markedly produced C4a, C3a, and C5a, whereas human albumin treated identically did not. White blood cells (WBC) treated by O2 bubbling significantly increased C3a levels alone, but at a much lesser grade than the Ig. A new priming method, i.e., homologous concentrated red cell (CRC) and human albumin was discerned from the experimental facts in-vitro, and we investigated the clinical effects of that priming method. C4a, C3a and C5a in BOG primed with homologous whole blood (HWB) were slightly higher than those in MOG during CPB. Those in the Ig-free priming group were more mildly increased than those in the HWB priming group, not only during CPB, but also after protamine administration; this tendency was clearer in BOG. It is concluded that (1) human immunoglobulin (Ig) denatured by O2 bubbling produces anaphylatoxins via the classical pathway; (2) WBC treated identically produces C3a at a far milder grade; (3) priming with CRC and human albumin reduces plasma anaphylatoxin levels; and (4) pulmonary function at an early postoperative period was improved in the homologous Ig-free priming group, especially with BOG.

Albumins↗

PubMed1989

Relevance of complotyping and subtyping of MHC class I gene products in haplotype definition for allogeneic bone marrow transplantation.

In preparation for a bone marrow transplantation 217 patients and their families were complotyped for Bf, C4A and C4B in addition to the routinely performed HLA-A,B,C,DR and HLA-D typing. In 147 families uncertainties in haplotype definition occurred which could be solved in 37 cases (25%) by complotyping. Additionally, patients and their relatives were subtyped for class I gene products by one-dimensional isoelectric focusing, a method by which serologically identical HLA-A, B, or C antigens could be split in five out of 22 cases tested. The results obtained clearly show the relevance of both methodologies for finding the best match of donor/recipient pairs to help to prevent MHC-induced graft-versus-host disease after bone marrow transplantation.

Bone Marrow Transplantation↗

PubMed1988

Antigenic determinants expressed by human C4 allotypes; a study of 325 families provides evidence for the structural antigenic model.

The antigenic determinants of human C4 have been defined by human IgG antisera, Rodgers (Rg) and Chido (Ch), in hemagglutination-inhibition assays (HAI). Eight (2 Rg and 6 Ch) are of high frequency, greater than 90%, and 1, WH, is of low frequency, 15%. The phenotypic combinations are complex; generally, C4A expresses Rg, and C4B has Ch, but reverse antigenicities have been established both by HAI and by sequence data of selected C4 allotypes. A study of 325 families provides data on the antigenic expression of each C4 allotype and demonstrates strong associations. A structural model for the antigenic determinants of C4 proteins has been proposed and is completely supported by the family material. Of the 16 possible antigenic combinations for C4 proteins, only 3 are undetected. A new Ch combination has been recorded in two French families. The reported sequence variation within the C4d region can account for the antigenic determinants but leaves the location of electrophoretic variation in C4 still unclear.

Blood Group Antigens↗

PubMed1991

Extended MHC haplotypes and CYP21/C4 gene organisation in Irish 21-hydroxylase deficiency families.

We have analysed fifteen classical 21-hydroxylase deficiency families from throughout Southern Ireland and report the serologically defined HLA-A, HLA-B, HLA-Cw, HLA-DR, C4A and C4B polymorphisms that characterize the inferred disease haplotypes. Additionally, we have used a combination of short and long range restriction mapping procedures in order to characterize the CYP21/C4 gene organization associated with individual serologically defined haplotypes. The results obtained indicate that disease haplotypes are characterized by a high frequency (33%) of CYP21B gene deletion and 8 out of 10 such deletion haplotypes are represented by the extended haplotype HLA-DR1, C4BQo, C4A3, HLA-B40(w60), HLA-Cw3, HLA-A3. Large scale length polymorphism in the CYP21/C4 gene cluster was found to conform strictly to a variable number of tandem repeats model with 4 alleles being detected. Disease haplotypes in which defective CYP21B gene expression is inferred to result from pathological point mutations show extensive diversity of associated HLA markers and include two examples of the extended HLA haplotype HLA-DR3, B8, Cw7, A1 haplotype, which has previously been reported to be negatively associated with 21-hydroxylase deficiency. One unusual disease haplotype has two CYP21 + C4 units, both of which appear to contain CYP21B-like genes.

Adrenal Hyperplasia, Congenital↗

PubMed1986

Biochemistry and biology of anaphylatoxins.

The molecular architecture of anaphylatoxins has been explored on several levels. Primary, secondary and tertiary structural parameters that dictate function of the C3a, C4a and C5a molecules are being elucidated with the aid of comparative sequence analyses, physical measurements and organic syntheses. Although C3a, C4a and C5a are biologically distinct mediators, as defined by their unique receptor systems, a common genetic origin is apparent from conserved features in their primary structures. Evidence is now available which suggests that similarities in the folding pattern of the anaphylatoxins may dictate a concensus conformation for each factor. We have learned from synthetic peptide studies that the binding (e.g. effector) site in anaphylatoxin molecules exists as a linear sequence contained in the C-terminal portion of the polypeptide. What is also evident is that a preferred conformation is defined for the binding site requiring a proper side chain orientation for optimal bioactivity. It is proposed that folding of the native structure stabilizes this conformation at the binding site. The binding site in C3a contains the essential residues LGLAR folded in an irregular or pseudo-beta-turn and stabilized by an adjacent alpha-helical segment. It is proposed that the alpha-helical segment influences orientation of the side chain residues in the 'binding site'. A similar model is evolving for C5a based on synthetic C5a peptides that express both spasmogenic and chemotactic activities. This helix turn model promises to be representative of an essential structural feature that determines anaphylatoxin activity. We believe that these models contribute significantly to our understanding of the molecular relationships between structure and function for these humoral mediators of inflammation.

Amino Acid Sequence↗

PubMed1985

Complotype genetic loci segregate more frequently with HLA-DR than with HLA-B.

The loci for BF, C2, C4A, and C4B are very closely linked to each other so that alleles of these plasma protein markers occur in populations in linkage disequilibrium and are inherited as single genetic units called complotypes. These complotypes are coded by a DNA region of the short arm of chromosome 6 embracing approximately 100 kilobases, which serve as a marker of the major histocompatibility complex. We have studied the complotypes of nine families with known HLA-B/DR crossovers. In seven families, the complotypes were inherited with HLA-DR, including in one family with a double recombination. The haplotype HLA-A28, Cw1, B27, FC3, 20, DR4 of JTr resulted from two recombinations between HLA-A2, Cw1, B27, SC42, DR7 and HLA-A28, Cwx or Cw1, B37, FC3, 20, DR4. In the remaining two families (Ro and Lo) the complotypes were inherited with HLA-B. The haplotype A2, Cw5, Bw44, SC30, DR3 of StLo resulted from paternal recombination between the haplotypes A2, Cw5, Bw44, SC30, DR4 and A24, B8, SC01, DR3, and the haplotype A24, Cw4, Bw35, SC31, DR3 of NaRo resulted from maternal recombination between A24, Cw4, Bw35, SC31, DR4 and A26, Bw41, FC31, DR3. Our data suggest that the complotype region maps closer to HLA-D than to HLA-B.

Complement C2↗

PubMed1999

Human leukocyte antigen class II and III alleles and severity of hepatitis C virus-related chronic liver disease.

Hepatitis C outcome is likely related both to viral factors and host's immune responses. We correlated the severity of liver disease with human leukocyte antigen (HLA) genes (C4A, C4B, TNFA, TNFB, DRB1, DRB3, DRB4, DRB5, DQA1, DQB1, TAP1, and TAP2) in three groups of subjects: 99 patients with chronic hepatitis, 41 asymptomatic carriers, and 179 uninfected controls. Patients with grade/stage 3 to 4 hepatitis significantly differentiated for their low frequency of alleles TNFB*1, DRB1*1104, and DRB3*03, which had a protective role, and high frequency of allele DRB1*1001, which was associated with disease severity. HLA-DRB*11 subtypes were differentially distributed: DRB1*1104 was most frequent in carriers, whereas DRB1*1101 was more frequent in patients. The TAP1C,2A haplotype was also underrepresented in patients with respect to controls. Finally, a decrease of heterozygous subjects was observed in patients with respect to carriers at the DQB1 locus. Multivariate analysis by correspondence analysis and multiple logistic regression indicated that age, sex, and hepatitis C virus (HCV) type were the strongest risk factors; however, some immunogenetic variables (TNFB*1, DRB1*1104, and DRB3*03) showed an independent contribution, especially in comparing patients with extreme manifestations of disease. The involvement of different genes in various HLA subregions suggests that anti-HCV responses are modulated by a complex gene interplay rather than by single alleles.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1984

Structure and function of the anaphylatoxins.

Chemical and physical characterization of the anaphylatoxin molecules have provided a reasonably clear description of the architecture of these bioactive proteins. The primary structures of C3a, C4a, and C5a from man and from a number of animal species have been elucidated, and it is apparent that the three anaphylatoxins are genetically related. The anaphylatoxin protein chains very in length from 74 to 78 residues and no fewer than 30% of the residues are homologous when comparing C3a, C4a, and C5a within or between species. Synthetic peptide studies have been instrumental in identifying molecular features essential for the function of anaphylatoxins. Information gleaned from the structure-function studies with synthetic analogue peptides of the anaphylatoxins define putative "active sites" in these effector molecules. Linear sequences at the carboxy-terminus of C3a and C4a fulfill all of the criteria of an "active site," in that synthetic peptides of an identical sequence can mimic the biologic actions of the natural factors. In the case of human C3a, a crystallographic analysis has been performed and a three-dimensional structure was elucidated at the 3.2 A level. The crystalline structure of C3a provides valuable new information regarding the alpha helical regions and identifies the arrangement of intra-chain disulfide linkages. Taken together, the structural data now accumulated for anaphylatoxins permit molecular modelling of these proteins, designates favored conformational arrangements of the native structures, and specifically localizes the effector sites. Furthermore, elements at the essential active site have been defined with such precision that models are proposed detailing the exact nature of ligand interactions between anaphylatoxins and specific cellular receptors. Biologic characterization of the anaphylatoxins continues at a rapid pace and each advance provides a clearer view of the role of these humoral mediators in host defense. A variety of responses to anaphylatoxins are known to occur at the cellular level and are mediated in a hormone-like fashion. Diversity of action for these factors at the tissue level is readily explained by the numerous cell types stimulated by the anaphylatoxins. Cellular responses to the anaphylatoxins are perhaps the most easily defined and studied; however, tissue and systemic effects more accurately reflect the physiologic role of anaphylatoxins. Considerable progress has been made in understanding the mechanisms whereby anaphylatoxins mediate two major tissue effects, namely enhancement of vascular permeability and induction of smooth muscle contraction.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

PubMed1983

Complement allotyping in SLE: association with C4A null.

Immunogenetic factors are important in systemic lupus erythematosus (SLE) and deficiency of a number of complement components is often associated with a lupus-like illness. The complement components Bf, C2 and C4 are encoded within the human major histocompatibility complex (MHC) and are polymorphic. A study of HLA and Bf and C4 polymorphism in 43 patients with SLE was undertaken firstly, to determine whether partial deficiency of C2 and C4 may predispose to disease and secondly, because it may allow the better definition of important supratypes associated with the disease and which may include the relevant disease gene(s). An increased frequency of C4A null alleles has been shown in SLE, with a minimal estimated C4A null gene frequency of 0.32 versus 0.20, but no case of partial C2 deficiency was identified. These results may indicate a direct role for partial C4 deficiency or that C4A null may be a marker for an important supratype which includes the relevant disease gene(s).

Complement C2↗

PubMed1988

The activation of C3 and C4 in human serum by immune complexes containing mouse monoclonal antibodies of different isotype and affinity: effects on solubilisation.

Radioimmunoassays for C3a and C4a have been used to measure the activation of complement in human serum by immune complexes containing DNP-BSA and each of 11 mouse anti-DNP monoclonal antibodies of varied isotype and affinity. When preformed complexes were added to serum, those containing IgG2 or IgM were potent activators of C4, whilst IgG1 complexes were less efficient. C3 activation in normal serum was similar for complexes containing IgG1, IgG2a, IgG2b or IgM. IgA complexes did not activate C3 or C4. Solubilisation of complexes was greatest for IgM and IgG2b and least for IgG2a and IgA. In serum containing Mg2+ EGTA C4 activation was abolished and the amount of C3 activation was lower for all IgG and IgM complexes. Antibodies of the same isotype did not necessarily activate complement to the same extent. Unexpectedly, three of the four IgMs activated C3 in EGTA. For IgMs, neither complement activation nor solubilisation correlated with affinity. For IgG1 antibodies, solubilisation was inversely proportional to affinity. C3 or C4 activation did not correlate with affinity.

Animals↗

PubMed1989

[Atopic dermatitis. II. The status of complement proteins and the pathogenetic role of anaphylatoxins C4a, C3a and C5a].

Eighty-eight patients with atopic dermatitis have been examined for the complementary proteins C3 (C3c), C3act., C4, C1inact. by radial immunodiffusion; in 36 of these patients anaphylatoxins C3a des Arg, C5a des Arg, and C4a des Arg have been radioimmunoassayed. Increased levels of C4a des Arg have been revealed in 50% of the examinees. C3a des Arg levels did not differ significantly from the reference values, and C5a des Arg level has been within the normal range in all the patients. C4a des Arg has been related to the severity of the skin inflammation and did not depend on the serum IgE content. C3 (C3c), C3act., C1inact. have been elevated and C4 reduced. These findings evidence activation of the complementary system in atopic dermatitis and indicate the role of anaphylatoxin C4a des Arg in the maintenance of the inflammatory reactions.

Adolescent↗

PubMed1985

Complement anaphylatoxins in idiopathic mixed cryoglobulinemia.

Basophil activation, observed in patients with idiopathic mixed cryoglobulinemia, has been related to the complement anaphylatoxins C4a, C3a and C5a. In the present study the plasma levels of the complement anaphylatoxins have been evaluated in 21 patients affected with idiopathic mixed cryoglobulinemia. The plasma concentration of C3a desArg was significantly higher in the patients than in the healthy controls; conversely the plasma values of C4a desArg were significantly lower. C5a desArg was not detectable in plasma from any subject. The high plasma level of C3a desArg in our patients may suggest a role for C3a anaphylatoxin in 'in vivo' basophil activation. No correlation was found between the plasma concentrations of C3a desArg or C4a desArg, the amount of cryoprecipitate and the clinical activity of the disease.

Adult↗

PubMed1986

Class III alleles and high-risk MHC haplotypes in type I diabetes mellitus, Graves' disease and Hashimoto's thyroiditis.

By typing a large quantity of family-based material for HLA-B, HLA-DR, C4, C2 and factor B, we were able to derive four-gene complement haplotypes (C4A, C4B, C2, BF) and six-gene MHC haplotypes (HLA-B, complement, HLA-DR). Fourteen six-gene MHC haplotypes showed linkage disequilibrium but exact frequencies could not be determined because it was not always possible to assign null C4 alleles in families where null genes were not clearly seen to segregate. Comparison of unrelated type I diabetes, Graves' disease and Hashimoto's thyroiditis patients with healthy unrelated controls revealed the following MHC allele associations: C4B*3, HLA-DR3 and HLA-DR4 with type I diabetes; BF*F1 and HLA-DR3 with Graves' disease; HLA-DR4 with Hashimoto's thyroiditis. By typing families of type I diabetes and Graves' disease patients we were able to derive two high-risk DR3+ MHC haplotypes for both type I diabetes and Graves' disease. These are HLA-B8 C4A*Q0 C4B*1 BF*S HLA-DR3 and HLA-B18 C4A*3 C4B*Q0 BF*F1 HLA-DR3, and these haplotypes account for most of the associations between these diseases and HLA-DR3. The MHC haplotype HLA-B15 C4A*3 C4B*3 BF*S HLA-DR4 also carries high risk for type I diabetes in this group of patients. Our data suggest that other DR4+ haplotypes, probably containing C4A*3 C4B*1, carry increased risk for type I diabetes whereas haplotypes containing DR4 and C4 C4A*3 C4B*Q0 do not. Our phenotype data suggest that DR4 in Hashimoto's thyroiditis is frequently associated with HLA-B44, C4A*3, C4B*1 and BF*S.

Alleles↗