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J M Moulds

Publications and source records attributed to J M Moulds.

At least 19 recordsLinked to original sources
PubMed2001

Ethnic diversity of class III genes in autoimmune disease.

One may wonder why the genes for the class III region are even situated in the human Major Histocompatibility Locus (MHC). However, on closer inspection we find that the genes for the complement components, tumor necrosis factor (TNF) and others may play an important role in host immune defenses. Thus, this region on chromosome six may be more appropriately thought of as an immune response area. Accordingly, there is a high degree of polymorphism in many genes within the MHC, the most notable being the HLA genes. In the class III region C2, factor B (Bf) and C4 are polymorphic in as many populations studied to date. The purpose of this review will be to briefly describe the class III region, identify the genetic polymorphism found in various ethnic groups and define their roles in autoimmune diseases.

Autoimmune Diseases↗
PubMed2001

Molecular identification of Knops blood group polymorphisms found in long homologous region D of complement receptor 1.

Complement receptor 1 (CR1) has been implicated in rosetting of uninfected red blood cells to Plasmodium falciparum-infected cells, and rosette formation is associated with severe malaria. The Knops blood group (KN) is located on CR1 and some of these antigens, ie, McCoy (McC) and Swain-Langley (Sl(a)), show marked frequency differences between Caucasians and Africans. Thus, defining the molecular basis of these antigens may provide new insight into the mechanisms of P falciparum malaria. Monoclonal antibody epitope mapping and serologic inhibition studies using CR1 deletion constructs localized McC and Sl(a) to long homologous repeat D of CR1. Direct DNA sequencing of selected donors identified several single nucleotide polymorphisms in exon 29 coding for complement control protein modules 24 and 25. Two of these appeared to be blood group specific: McC associated with K1590E and Sl(a) with R1601G. These associations were confirmed by inhibition studies using allele-specific mutants. A sequence-specific oligonucleotide probe hybridization assay was developed to genotype several African populations and perform family inheritance studies. Concordance between the 1590 mutation and McC was 94%; that between Sl(a) and 1601 was 88%. All but 2 samples exhibiting discrepancies between the genotype and phenotype were found to be due to low red cell CR1 copy numbers, low or absent expression of some alleles, or heterozygosity combined with low normal levels of CR1. These data further explain the variability observed in previous serologic studies of CR1 and show that DNA and protein-based genetic studies will be needed to clarify the role of the KN antigens in malaria.

Animals↗
PubMed2001

Genetic, structural and functional diversities of human complement components C4A and C4B and their mouse homologues, Slp and C4.

The complement protein C4 is a non-enzymatic component of the C3 and C5 convertases and thus essential for the propagation of the classical complement pathway. The covalent binding of C4 to immunoglobulins and immune complexes (IC) also enhances the solubilization of immune aggregates, and the clearance of IC through complement receptor one (CR1) on erythrocytes. Human C4 is the most polymorphic protein of the complement system. In this review, we summarize the current concepts on the 1-2-3 loci model of C4A and C4B genes in the population, factors affecting the expression levels of C4 transcripts and proteins, and the structural, functional and serological diversities of the C4A and C4B proteins. The diversities and polymorphisms of the mouse homologues Slp and C4 proteins are described and contrasted with their human homologues. The human C4 genes are located in the MHC class III region on chromosome 6. Each human C4 gene consists of 41 exons coding for a 5.4-kb transcript. The long gene is 20.6 kb and the short gene is 14.2 kb. In the Caucasian population 55% of the MHC haplotypes have the 2-locus, C4A-C4B configurations and 45% have an unequal number of C4A and C4B genes. Moreover, three-quarters of C4 genes harbor the 6.4 kb endogenous retrovirus HERV-K(C4) in the intron 9 of the long genes. Duplication of a C4 gene always concurs with its adjacent genes RP, CYP21 and TNX, which together form a genetic unit termed an RCCX module. Monomodular, bimodular and trimodular RCCX structures with 1, 2 and 3 complement C4 genes have frequencies of 17%, 69% and 14%, respectively. Partial deficiencies of C4A and C4B, primarily due to the presence of monomodular haplotypes and homo-expression of C4A proteins from bimodular structures, have a combined frequency of 31.6%. Multiple structural isoforms of each C4A and C4B allotype exist in the circulation because of the imperfect and incomplete proteolytic processing of the precursor protein to form the beta-alpha-gamma structures. Immunofixation experiments of C4A and C4B demonstrate > 41 allotypes in the two classes of proteins. A compilation of polymorphic sites from limited C4 sequences revealed the presence of 24 polymophic residues, mostly clustered C-terminal to the thioester bond within the C4d region of the alpha-chain. The covalent binding affinities of the thioester carbonyl group of C4A and C4B appear to be modulated by four isotypic residues at positions 1101, 1102, 1105 and 1106. Site directed mutagenesis experiments revealed that D1106 is responsible for the effective binding of C4A to form amide bonds with immune aggregates or protein antigens, and H1106 of C4B catalyzes the transacylation of the thioester carbonyl group to form ester bonds with carbohydrate antigens. The expression of C4 is inducible or enhanced by gamma-interferon. The liver is the main organ that synthesizes and secretes C4A and C4B to the circulation but there are many extra-hepatic sites producing moderate quantities of C4 for local defense. The plasma protein levels of C4A and C4B are mainly determined by the corresponding gene dosage. However, C4B proteins encoded by monomodular short genes may have relatively higher concentrations than those from long C4A genes. The 5' regulatory sequence of a C4 gene contains a Spl site, three E-boxes but no TATA box. The sequences beyond--1524 nt may be completely different as the C4 genes at RCCX module I have RPI-specific sequences, while those at Modules II, III and IV have TNXA-specific sequences. The remarkable genetic diversity of human C4A and C4B probably promotes the exchange of genetic information to create and maintain the quantitative and qualitative variations of C4A and C4B proteins in the population, as driven by the selection pressure against a great variety of microbes. An undesirable accompanying byproduct of this phenomenon is the inherent deleterious recombinations among the RCCX constituents leading to autoimmune and genetic disorders.

Amino Acid Sequence↗
PubMed2000

Mapping of the region of complement receptor (CR) 1 required for Plasmodium falciparum rosetting and demonstration of the importance of CR1 in rosetting in field isolates.

The malaria parasite Plasmodium falciparum induces a number of novel adhesion properties in the erythrocytes that it infects. One of these properties, the ability of infected erythrocytes to bind uninfected erythrocytes to form rosettes, is associated with severe malaria and may play a direct role in the pathogenesis of disease. Previous work has shown that erythrocytes deficient in complement receptor (CR) 1 (CR1, CD35; C3b/C4b receptor) have greatly reduced rosetting capacity, indicating an essential role for CR1 in rosette formation. Using deletion mutants and mAbs, we have localized the region of CR1 required for the formation of P. falciparum rosettes to the area of long homologous repeat regions B and C that also acts as the binding site for the activated complement component C3b. This result raises the possibility that C3b could be an intermediary in rosetting, bridging between the infected erythrocyte and CR1. We were able to exclude this hypothesis, however, as parasites grown in C3-deficient human serum formed rosettes normally. We have also shown in this report that rosettes can be reversed by mAb J3B11 that recognizes the C3b binding site of CR1. This rosette-reversing activity was demonstrated in a range of laboratory-adapted parasite strains and field isolates from Kenya and Malawi. Thus, we have mapped the region of CR1 required for rosetting and demonstrated that the CR1-dependent rosetting mechanism occurs commonly in P. falciparum isolates, and could therefore be a potential target for future therapeutic interventions to treat severe malaria.

Animals↗
PubMed2000

Identification of complement receptor one (CR1) polymorphisms in west Africa.

Complement receptor one (CR1) is a ligand for the rosetting of Plasmodium falciparum infected red cells with uninfected cells. Since CR1 exhibits three known polymorphisms, we studied European-Americans (n = 112) and African-Americans (n = 330) and Malians (n = 158) to determine if genetic differences existed in an area endemic for malaria that could offer a survival advantage. The frequencies of Knops blood group phenotypes McC(b+) and Sl(a-) were greatly increased in Africans vs Europeans. Although the frequency of McC(b+) was similar between Africans from the USA or Mali, the Sl(a-) phenotype was significantly higher in Mali (39% vs 65%, respectively). There was an increased frequency of the largest size (250 kD) of CR1 in Mali, but this did not differ significantly from the USA (P = 0.09). Both cohorts of Africans had higher expression of red cell CR1 than European-Americans but this showed little difference between the USA and Mali groups. Thus, the most important CR1 polymorphism relevant to rosetting of malaria infected cells appears to be the Knops blood group.

Blood Group Antigens↗
PubMed2000

Blood group associations with parasites, bacteria, and viruses.

Although recent investigations into the human blood groups have proceeded mainly at the molecular level, the RBC remains an exquisite model to study the expression of various genes and their related proteins. Although DNA may be informative, it may not always give meaningful information regarding protein expression on cell surfaces, which is where binding occurs. Because of their easy accessibility, RBCs will continue to be used as a major tool in the investigation of the causative agents for disease, whether they be viral, bacterial, or parasitic in nature.

Animals↗
PubMed1999

Complement receptor 1 red cell expression is not controlled by the In(Lu) gene.

BACKGROUND: The In(Lu) gene reportedly suppresses several blood group antigens that are not part of the Lutheran system, including the high-incidence antigens of the Knops blood group system. Because complement receptor 1 (CR1), which is known to carry the Knops system antigens, has a red cell (RBC) expression polymorphism, the role of In(Lu) in the expression of the Knops system antigens was reinvestigated. STUDY DESIGN AND METHODS: Blood samples from nine donors having the Lu(a-b-) phenotype were obtained and immediately phenotyped for Lu(b), Kn(a), McC(a), Sl(a), and Yk(a). The samples were also tested for Lu(a), P1, and AnWj. Immunoblots were performed to study both the CR1 and Lutheran glycoproteins from these donors. RBC expression of CR1 was quantified with an enzyme-linked immunosorbent assay, and the genetic inheritance of the high-expression (H) or low-expression (L) allele for CR1 was determined by Southern blot. RESULTS: Lu(b) was demonstrable only by absorption and elution techniques on all nine samples; however, the high-incidence Knops system antigens were readily detectable by hemagglutination. Two Lu(a-b-) donors (sibs) demonstrated weak Lutheran glycoprotein bands of 78 and 85 kDa on immunoblots, while the other seven Lu(a-b-) samples had no detectable glycoprotein. All donors had CR1*1, and one donor also had CR1*2 on immunoblot. Only one donor was homozygous for the L allele, and all had RBC copy numbers of CR1 within the normal range. CONCLUSIONS: Nine donors with the Lu(a-b-) phenotype showed suppression of the Lutheran system antigens but normal expression of CR1 glycoprotein and the Knops system blood group antigens. This suggests that the genes that suppress Lutheran system antigens do not suppress CR1 or its related blood group antigens.

Alleles↗
PubMed1999

Systemic lupus erythematosus in three ethnic groups: III. A comparison of characteristics early in the natural history of the LUMINA cohort. LUpus in MInority populations: NAture vs. Nurture.

AIM: To determine and contrast the socioeconomic-demographic and clinical features of patients with recent onset (< or =5 y) systemic lupus erythematosus (SLE) from three ethnic groups, Hispanic, African-American and Caucasian (H, AA, C). SUBJECTS AND METHODS: SLE cases (American College of Rheumatology criteria) (incident (n = 56), prevalent (n = 173)), were enrolled in a longitudinal study at The University of Alabama at Birmingham, The University of Texas-Houston Health Science Center and The University of Texas Medical Branch at Galveston. Socioeconomic-demographic, clinical, immunological, behavioral and psychological data were obtained using validated instruments and standard laboratory techniques, and compared. RESULTS: 70 H, 88 AA and 71 C SLE patients constitute this cohort. H and AA patients were younger and of lower socioeconomic-demographic status. They also had evidence of more frequent organ system involvement (renal, cardiovascular), more auto-antibodies, more active disease (after adjusting for discrepant socioeconomic-demographic features), lower levels of social support and more abnormal illness-related behaviors (more in H than in AA). H also were more likely to have an abrupt disease onset; C were more likely to be on antimalarials but less likely to be on corticosteroids. H, AA, and C used health care resources comparably. They had similar levels of pain and physical and mental functioning after adjusting for age, disease duration, income, education, social support, illness-related behaviors, and Systemic Lupus Activity Measure or SLAM scores. CONCLUSIONS: H and AA patients have more active SLE, at an earlier age of onset, and a less favorable socioeconomic-demographic structure (worse among the H than AA) which predispose them to a less favorable natural history.

Adolescent↗
PubMed1998

Systemic lupus erythematosus in three ethnic groups: I. The effects of HLA class II, C4, and CR1 alleles, socioeconomic factors, and ethnicity at disease onset. LUMINA Study Group. Lupus in minority populations, nature versus nurture.

OBJECTIVE: To study the relative impact of immunogenetic versus socioeconomic factors on systemic lupus erythematosus (SLE) at disease onset/presentation. METHODS: Medical records regarding SLE onset/ presentation were abstracted on 229 SLE patients who were enrolled in a prospective lupus outcome study. Patients were grouped in equivalent proportions of Caucasians, African Americans, and Hispanics. HLA-DRB1, DQA1, and DQB1 oligotyping, as well as C4 and CR1 allotyping, were carried out by standard methods. In addition to these genetic factors, data on ethnicity, age at SLE onset, monthly income, level of education, and home ownership were entered into stepwise logistic or stepwise multiple linear regression models as independent variables, and each specific clinical feature (neurologic, renal, and cardiovascular disease due to SLE), as well as the total Systemic Lupus Activity Measure (SLAM) score and physician's global assessment of disease activity at disease onset, were entered as dependent variables. RESULTS: HLA-DRB1*0301 (DR3), DRB1*1503 (DR2), and DRB1*08 (DR8) alleles were more frequently found in Caucasians, African Americans, and Hispanics, respectively. Hispanics were more likely to have cardiac and renal disease, as well as a higher physician's global assessment of disease activity. African Americans were more likely to have neurologic disease, renal disease, and a higher SLAM score. Those with less education had a higher SLAM score. Patients with HLA-DRB1*01 had less renal disease and a lower SLAM score. Those with C4A*3 alleles had a higher SLAM score and a higher physician's global assessment of disease activity. CONCLUSION: Both genetic and socioeconomic determinants, as well as other factors associated with Hispanic and African-American ethnicity, affect the presentation of SLE.

Adolescent↗
PubMed1998

Systemic lupus erythematosus in three ethnic groups: II. Features predictive of disease activity early in its course. LUMINA Study Group. Lupus in minority populations, nature versus nurture.

OBJECTIVE: To determine the factors associated with disease activity in patients with recent-onset (< or =5 years) systemic lupus erythematosus (SLE) who were of Hispanic, African-American, or Caucasian ethnicity. METHODS: Incident and prevalent cases of SLE, as defined by the American College of Rheumatology criteria for SLE, among the 3 ethnic groups were identified in Alabama (The University of Alabama at Birmingham) and Texas (The University of Texas-Houston Health Science Center and The University of Texas Medical Branch at Galveston). Variables from the sociodemographic, clinical, immunologic, immunogenetic, behavioral, and psychological domains were obtained using validated instruments. Disease activity was ascertained with the Systemic Lupus Activity Measure (SLAM). Stepwise domain regressions with SLAM score as the dependent variable were performed. Final ethnic-specific and overall regression models were obtained by entering variables that were retained in the domain regressions. RESULTS: SLAM scores at study entry were higher in the African Americans (mean +/- SD 12.6 +/- 6.9) and Hispanics (11.0 +/- 6.2) than in the Caucasians (8.5 +/- 3.7) (P < or = 0.001). The final overall regression model (R2 = 28%) for higher SLAM score included the following variables: African-American ethnicity, lack of private health insurance, abrupt disease onset, presence of anti-Ro antibodies, absence of HLA-DRB1*0301, higher levels of helplessness, and abnormal illness-related behaviors. CONCLUSION: Socioeconomic, immunologic, immunogenetic, behavioral, and psychological variables were all predictive of disease activity early in the course of SLE, irrespective of ethnic group. However, there remain ethnic group differences in disease activity that were not explained by these factors.

Adolescent↗
PubMed1998

Reference typing report for complement component C4.

During the 7th Complement Genetics Workshop, Mainz, Germany, May 1998, a complement component C4 typing exercise took place with the aim of applying present technologies to the definition of reference C4 alleles/phenotypes and the recognition of nonexpressed (Q0) C4 alleles within expressed haplotypes. Eleven samples were submitted from 3 laboratories and tested by 14 participating laboratories with basic protein-typing technologies; in addition, each laboratory contributed data from local expertise. The samples were introduced to the reference typing for one or more characteristic allotype or for partial or total nonexpression of one isotype. The blinded samples were centrally evaluated and the results discussed among the participants at a plenum meeting. From the results, the samples could be classified into a group of common, easy to diagnose pheno-/allotypes, less common but still unanimously recognised variants, and a third group with difficult pheno-/allotypes. Within the latter group, the allotypes were either new (C4A '92'; C4B '93') and/or showed partial or total reversed antigenicity and unusual Rodgers/Chido (Rg/Ch) PCR subtypes (C4A '92'; C4A 12; C4B '35'; C4B '13'). Semiquantitative C4-alpha-chain estimates of relative isotype levels correlated well with the number of alleles seen at each locus by agarose gel electrophoresis, and were superior to other isotype quantitation methods. From the evaluation of the reference typing it was concluded that the recognition of rare, aberrant or hybrid C4 alleles with partial or total reversed Rg/Ch antigenicity or monoclonal reactivity is still difficult in most instances; besides isotype-dependent lysis, relative migration values, immunoblots with Rg- and Ch-specific monoclonal antibodies, Rg/Ch PCR typing, side-by-side comparison with already described allotypes will ultimately be required. The recognition of nonexpressed alleles within C4A and C4B expressed phenotypes remains the major obstacle in C4 genetic typing. Finally, a conclusive interpretation of DNA typing results will be achieved only in the context of complete allotyping results at the protein level, and at present cannot replace conventional protein allotyping.

Alleles↗
PubMed1998

Reference typing report for complement receptor 1 (CR1).

A total of 100 Chinese blood donors (50 from Shen-Zhen and 50 from Taiwan) were studied by the participants in addition to 9 reference samples. A new nomenclature for the CR1 structural alleles was recommended by the participants which would use a numbering system, e.g. CR1*1. The structural allele frequencies in the Chinese were: CR1*1 (190 kD) 0.96, CR1*2 (220 kD) 0.03, CR1*3 (160 kD) 0.01 and CR1*4 (250 kD) 0.00. The HindIII expression polymorphism was also studied and the high expressing allele had a gene frequency of 0.71 while the low expressor gene frequency was 0.28. Erythrocyte copy numbers were quantified and compared between laboratories with good correlation (R = 0.55-0.88). The mean (+/- SD) erythrocyte copy number was 463 (+/- 229) in the Taiwan donors and 446 (+/- 207) in the Mainland Chinese.

Alleles↗
PubMed1998

DNA analysis of Duffy genes in American blacks.

BACKGROUND: Because limited studies have shown that the Duffy genotype is not accurately reflected by the erythrocyte phenotype, we used PCR-RFLP to determine the true FY1 and FY2 gene frequencies in blacks. METHODS: Genomic DNA was extracted from 81 randomly selected black individuals, amplified using PCR, digested with BanI and electrophoresed in 1.8% gels. Direct DNA sequencing of the FY regulatory region was done on a sample which had weak Fyb antigens. Standard serological techniques were used to type the erythrocytes for Fya and Fyb. RESULTS: The most common genotype (83%) in blacks was Fy(a-b+) but almost all of the samples serologically typed as Fy(a-b-). The new gene frequencies are 0.08 for FY1 and 0.92 for FY2. Two donors whose erythrocytes typed weakly positive for Fyb and appeared to be Fyx were homozygous for FY2 by DNA testing. DNA sequencing of the regulatory region for Duffy found a mutation in an Sp1 binding site in the Fyx donor. CONCLUSIONS: We conclude that (1) the FY2 gene occurs in a much higher frequency in blacks than previously reported which may explain the lack of anti-Fyb in this ethnic group and (2) Fyx appears to be a the product of a mutant FY2 gene giving a quantitative variation in expression.

Black People↗
PubMed1997

P. falciparum rosetting mediated by a parasite-variant erythrocyte membrane protein and complement-receptor 1.

The factors determining disease severity in malaria are complex and include host polymorphisms, acquired immunity and parasite virulence. Studies in Africa have shown that severe malaria is associated with the ability of erythrocytes infected with the parasite Plasmodium falciparum to bind uninfected erythrocytes and form rosettes. The molecular basis of resetting is not well understood, although a group of low-molecular-mass proteins called rosettins have been described as potential parasite ligands. Infected erythrocytes also bind to endothelial cells, and this interaction is mediated by the parasite-derived variant erythrocyte membrane protein PfEMP1, which is encoded by the var gene family. Here we report that the parasite ligand for rosetting in a P. falciparum clone is PfEMP1, encoded by a specific var gene. We also report that complement-receptor 1 (CR1) on erythrocytes plays a role in the formation of rosettes and that erythrocytes with a common African CR1 polymorphism (S1(a-)) have reduced adhesion to the domain of PfEMP1 that binds normal erythrocytes. Thus we describe a new adhesive function for PfEMP1 and raise the possibility that CR1 polymorphisms in Africans that influence the interaction between erythrocytes and PfEMP1 may protect against severe malaria.

Africa↗