Biomedical subjects
M F Moffatt
Publications and source records attributed to M F Moffatt.
Association of atopic dermatitis to the beta subunit of the high affinity immunoglobulin E receptor.
IgE dysregulation is a major pathogenic feature of atopic dermatitis and other IgE-mediated allergic diseases such as asthma and rhinitis. Allergen complexed to IgE binds to the high affinity receptor for IgE (Fc epsilon RI) on the surface of epidermal Langerhans cells, mast cells and basophils, triggering the release of inflammatory mediators. The beta subunit of Fc epsilon RI has been localized to human chromosome 11q12-13, and variants within this gene have been shown to associate with asthma and measures of atopy. We have tested several polymorphisms within Fc epsilon RI-beta for association to atopic dermatitis in a panel of 60 families (panel A), recruited through a proband with atopic dermatitis. The findings were tested in a second panel of families (panel B). Significant sharing of maternal alleles was seen for atopic dermatitis and allele 2 of RsaI intron 2 (RsaIvin2*2) (P = 0.0022) and allele 1 of RsaI exon 7 (RsaIvex7*1) (P = 0.0036) Fc epsilon RI-beta gene polymorphisms. These findings were replicated in Panel B, confirming the association of Fc epsilon RI-beta RsaI polymorphisms with atopic dermatitis. The combined significance of the association of atopic dermatitis to RsaI polymorphisms was P = 0.0002 (RsaIvin2*2) and P = 0.00034 (RsaIvex7*1). The polymorphisms also showed association with asthma: P = 0.0068 (RsaIvin2*2) and P = 0.018 (RsaIvex7*1). Polymorphisms within the Fc epsilon RI-beta gene are strongly associated with atopic dermatitis.
The genetics of asthma. Maternal effects in atopic disease.
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A genome scan for loci influencing total serum immunoglobulin levels: possible linkage of IgA to the chromosome 13 atopy locus.
Immunoglobulins play an essential part in the immune system, and immunoglobulin deficiencies can have profound medical consequences. The genetic control and regulation of the immunoglobulin response is therefore of interest. Previous investigations have identified a number of loci influencing total and specific IgE levels. In this study, 80 nuclear families have been examined for linkage of total serum IgA, IgG and IgM levels to a genome-wide panel of microsatellite markers. Potential quantitative trait loci influencing IgA levels have been identified on chromosomes 10 and 13, and possible loci influencing IgG levels were found on chromosomes 3 and 13. No significant linkages to IgM levels were found. The linkage of IgA on chromosome 13 was to a marker previously linked to IgE responses (atopy). Linkage to IgG was in the same region but to a more distal marker. None of the factors known to influence immunoglobulin expression map to the loci identified in the present study. These loci are therefore likely to contain previously unrecognized components of the immunoregulatory system.
Gene identification in asthma and allergy.
Asthma and atopy are due to the interaction between genetic and environmental factors. The genetic basis of asthma and atopy is becoming more certain, with the promise of improvements in the diagnosis and treatment of these disorders. A combination of candidate gene and positional cloning studies has already identified several genes which influence allergic disease. These genes predispose in general to atopy, or influence the specific IgE response to individual allergens, or enhance inflammation independently of atopic mechanisms. In addition to these known factors, the chromosomal localisation of other putative genes is becoming clear.
Asthma: an epidemic in the absence of infection?
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Germline TCR-A restriction of immunoglobulin E responses to allergen.
Immunoglobulin E responses to known environmental antigens (allergens) may serve as a general model to investigate germline genetic restriction of the immune response. We have previously shown genetic linkage between IgE responses to major allergens and the T-cell receptor (TCR) A/D locus, but not to TCR-B, implying that elements in TCR A/D restrict the ability to react to specific antigens. We now show, in two sets of subjects from the same population, a strong allelic association between a VA8.1 polymorphism (VA8.1(*)2) and reactivity to Der p II, a major antigenic component of the house dust mite Dermatophagoides pteronyssinus. Association was also seen between Der p II IgE titres and HLA-DRB1(*)1501 alleles. Reactivity to Der p II was confined to subjects who were positive for VA8.1(*)2 and HLA-DRB1(*)1501, demonstrating germline HLA-DR and TCR-A interaction in restricting the response to exogenous antigen.
Fc epsilon R1-beta polymorphism and total serum IgE levels in endemically parasitized Australian aborigines.
Endemic helminthic infection is a major public-health problem and affects a large proportion of the world's population. In Australia, helminthic infection is endemic in Aboriginal communities living in tropical northern regions of the continent. Such infection is associated with nonspecific (polyclonal) stimulation of IgE synthesis and highly elevated total serum IgE levels. There is evidence that worm-infection variance (i.e., human capacity of resistance) and total serum IgE levels may be related to the presence of a major codominant gene. The beta chain of the high-affinity IgE receptor, Fc epsilon R1-beta, has been previously identified as a candidate for the close genetic linkage of the 11q13 region to IgE responses in several populations. We show a biallelic RsaI polymorphism in Fc epsilon R1-beta to be associated with total serum IgE levels (P = .0001) in a tropical population of endemically parasitized Australian Aborigines (n = 234 subjects). The polymorphism explained 12.4% of the total residual variation in serum total IgE and showed a significant (P = .0000) additive relationship with total serum IgE levels, across the three genotypes. These associations were independent of familial correlations, age, gender, racial admixture, or smoking status. Alleles of a microsatellite repeat in intron 5 of the same gene showed similar associations. The results suggest that variation in Fc epsilon R1-beta may regulate IgE-mediated immune responses in this population.
Tumour necrosis factor haplotypes and asthma.
Airway inflammation is a prominent feature of asthma. The pro-inflammatory cytokine Tumour Necrosis Factor shows constitutional variation in its level of secretion, which is linked to polymorphisms within the TNF gene complex and the surrounding MHC. In this study, 413 subjects in 88 nuclear families from a general population sample were examined for association with asthma and TNF polymorphisms. Ninety-two subjects were asthmatic, as defined by questionnaire. Asthma was significantly more common in subjects with allele 1 of the LT alpha NcoI polymorphism (LT alpha NcoI*1) (p = 0.005), and allele 2 of the TNF-308 polymorphism (TNF-308*2) (p = 0.004). The association was confined to the LT alpha NcoI*1/TNF-308*2 haplotype, so that it was not possible to differentiate between the effects of LT alpha NcoI and TNF-308 alleles. The HLA-DR locus was excluded as a cause of this association. The results suggest that genetic influences on inflammation may be important in the pathogenesis of asthma.
Linkage and candidate gene studies in asthma.
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Sensitivity to bee and wasp venoms: association with specific IgE responses to the bee and wasp venom and HLA DRB1 and DPB1.
BACKGROUND: Stings from bees and wasps can cause systemic reactions which can be fatal in some individuals. In these venom-sensitive patients, specific IgE to the venom is produced and is considered to participate in the adverse reactions. This immune response requires antigen presentation by human leucocyte antigens (HLA) class II molecules, which includes DR and DP, which are present on antigen presenting cells. OBJECTIVE: To test for associations between HLA class II DRB1 and DPB1 alleles and life-threatening sensitivity to both bee and wasp venoms. To establish further whether any associations are independent of the atopy phenotype. METHODS: A total of 33 bee- and 44 wasp-venom-sensitive patients was studied. DRB1 genotypes were determined by single stranded oligonucleotide (SSO) probing of PCR products, and DPB1 genotypes by amplified fragment length polymorphism (AFLP) analysis. Total and specific IgE were measured using the Pharmacia Immunocap, FEIA. Patients with specific IgE to the venom antigens only were termed monosensitive and those with additional specific IgE to HDM and/or GP were termed polysensitive. RESULTS: Allele frequencies were compared to an unrelated control population. The 33 bee-sensitive patients had a greater prevalence of DRB1*07 alleles than the control subjects, 26% vs 14%, with an odds ratio (OR) of 2.1 (95% CI, 1.2-3.7, P = 0.015, corrected for multiple comparisons, Pc = ns). This association was confined to the 15 monosensitive bee patients, who had a 43% DRB1*07 allele frequency when compared with 11% in the 18 polysensitive bee patients, OR 6.1 (95% CI, 1.73-22, P = 0.004, Pc = 0.05), and when compared with a control group of non-venom subjects, 43% vs 16%, OR 3.9 (95% CI, 1.72-9.0, P = 0.002, Pc = 0.02). The 44 wasp-sensitive patients had an increase in the DRB1*11 allele when compared with the control subjects, 13% vs 6%, with an OR 2.2 (95% CI, 1.0-4.6, P = 0.04, Pc = NS), and a decreased prevalence of DRB1*04 alleles, 10% vs 19%, with an OR 0.33 (95% CI, 0.24-0.99, P = 0.04, Pc = NS), but these were not significant when multiple comparisons were taken into account. The DPB1 alleles were not significantly different between the venom sensitive patients and the controls. CONCLUSION: Patients monosensitive to bee venom had a significantly greater prevalence of DRB1*07 alleles than the non-venom, control population suggesting that IgE responses in these patients may, in part be controlled by immune response HLA class II genes. These results are also suggestive of wasp-sensitive patients having a higher prevalence of DRB1*11 and a lower prevalence of DRB1*04 than the control population.
The genetics of specific allergy.
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A genetic map of chromosome 11q, including the atopy locus.
Atopy is a common and genetically heterogeneous syndrome predisposing to allergic asthma and rhinitis. A locus linked to the atopy phenotype has been shown to be present on chromosome 11q12-13. Linkage has only been seen in maternally derived alleles. We have constructed a genetic linkage map of the region, using 15 markers to span approximately 27 cM, and integrate previously published maps. Under a model of maternal inheritance, the atopy locus is placed within a 7-cM interval between D11S480 and D11S451. The interval contains the important candidate gene FCERIB.
Genetic linkage of T-cell receptor alpha/delta complex to specific IgE responses.
IgE responses to inhaled proteins underlie the clinical syndrome of allergic (atopic) asthma and rhinitis. We have investigated genetic linkage between specific IgE reactions to highly purified major allergens and the T-cell receptor (TCR) alpha and beta gene complexes on chromosome 14 and 7, respectively. Antigens tested included highly purified proteins from the housedust mite Dermatophagoides pteronyssinus, the domestic cat and dog, grass pollen, and the mould Alternaria alternata. Affected sibling-pair methods were used in two independent sets of families, one in the UK and one in Australia. No linkage of IgE serotypes to TCR-beta was detected, but significant linkage to TCR-alpha was seen in both family groups. For several of the IgE phenotypes investigated (positive responses to whole allergen sources or purified antigens or serum IgE above the 70th percentile in the population) the affected sibling-pairs showed significant sharing of TCR-alpha microsatellite alleles from both parents. The results show that a gene (or genes) in the TCR-alpha region modifies specific IgE responses.
Localisation of atopy and beta subunit of high-affinity IgE receptor (Fc epsilon RI) on chromosome 11q.
Atopy, a common familial syndrome underlying allergic asthma and rhinitis, is characterised by sustained immunoglobulin E (IgE) responses to common allergens. We have previously shown genetic linkage of atopy to the chromosome 11q13 marker D11S97 (pms51) through maternally derived alleles, but no likely candidate genes were known to lie near this marker. We have analysed maternally derived alleles from 155 sibling-pairs affected by atopy to seek evidence of linkage between the gene predisposing to atopy and other markers on chromosome 11q13. We found that the beta subunit of the high-affinity receptor for IgE (Fc epsilon RI-beta) also lies on chromosome 11q13, and that it is in close genetic linkage with the gene for atopy. The known roles of Fc epsilon RI in antigen-induced mast-cell degranulation and in the release of cytokines that enhance IgE production make the gene for its beta subunit a candidate for the chromosome 11 atopy locus.
Dinucleotide repeat polymorphism at the D11S480 locus.
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Maternal inheritance of atopic IgE responsiveness on chromosome 11q.
Atopy is a common familial state underlying allergic asthma and rhinitis. Lately, we have assigned a gene for atopy to chromosome 11q by linkage to the marker D11S97. Since previous studies have suggested that the risk of atopy is higher for children of atopic mothers than for those of atopic fathers, we sought differences between maternal and paternal patterns of transmission at the 11q13 locus among pairs of siblings in families affected by atopy. When we defined atopy as the presence of a positive skinprick test (greater than or equal to 2 mm) to any of a panel of common allergens, a higher than normal concentration of total serum IgE, or a positive radioallergosorbent test for a specific IgE, we found that 125 (62%) of the sibling-pairs affected by atopy shared the maternal 11q13 allele and 78 (38%) did not. This distribution differs significantly from the expected 50/50 distribution (p = 0.001). Of paternally derived alleles, 83 (46%) were shared and 96 (54%) were not (not significantly different from 50/50). The result was similar whatever definition of atopy was used and with other genetic markers on 11q. These findings show that transmission of atopy at the chromosome 11q locus is detectable only through the maternal line. The pattern of inheritance is consistent either with paternal genomic imprinting or with maternal modification of developing immune responses.
Factors confounding genetic linkage between atopy and chromosome 11q.
The results of testing for linkage between atopy and the chromosome 11 marker D11S97 is shown for all the 723 subjects genotyped by us up to January 1992. Lod score estimations were confounded by the high population prevalence of atopy, maternal inheritance of atopy at the 11q locus, genetic heterogeneity, and excess of atopy in families not ascertained through a single proband. Affected sib-pair analysis shows evidence for linkage which is not dependent on the definition of atopy or model specification. We suggest that presentation of sib-pair data will be suitable for meta-analysis of the different studies of genetic linkage and atopy.