Genetic and immunologic basis of atopic responses

Prevalence of specific allergic diseases in school children as related to parental atopy

BACKGROUND

Our objective was to investigate the influence of parental allergy on the manifestations and course of allergic disease in children.

METHODS AND RESULTS

A total of 15,234 school children aged 6 and 9 years were evaluated by means of questionnaires completed by their parents in a cross-sectional survey conducted in Tokushima, Japan. The prevalence and relative risk ratio (RRR) for parental allergy in children with atopic dermatitis, asthma and allergic rhinitis were 6.4% (RRR 2.5), 3.2% (RRR 2.4) and 15% (RRR 2.4), respectively. The risk of atopic dermatitis was particularly high in children whose parent had atopic dermatitis, with an RRR of 2.8 (father) and 3.7 (mother). Children with a parental history of asthma also had a high risk of that disorder (RRR of father 5.3, mother 6.2). However, the risk of allergic rhinitis was no different in children with a parental history of allergic rhinitis or from children with a parental history of asthma and atopic dermatitis. A history of allergic disease in both parents, especially of asthma and atopic dermatitis, increased the risk of allergic disease in the child. Milder symptoms, such as wheezy bronchitis, in schoolchildren were similarly related with the same hereditary tendency as the identical allergic disease. The disappearance of allergic symptoms with age also related to a hereditary component, being less likely in children with a history of parental allergy than in those without such an atopic history.

CONCLUSIONS

The manifestations and course of allergic disease in school children relate to parental allergic disease.

Genetic regulation of Dermatophagoides pteronyssinus-specific IgE responsiveness: a genome-wide multipoint linkage analysis in families recruited through 2 asthmatic sibs. Collaborative Study on the Genetics of Asthma (CSGA)

BACKGROUND

Dermatophagoides pteronyssinus (Der p) is one of the most frequently implicated allergens in atopic diseases. Although HLA could play an important role in the development of the IgE response to the Der p allergens, genetic regulation by non-HLA genes influences certain HLA-associated IgE responses to complex allergens.

OBJECTIVE

To clarify genetic control for the expression of Der p-specific IgE responsiveness, we conducted a genome-wide search for genes influencing Der p-specific IgE antibody levels by using 45 Caucasian and 53 African American families ascertained as part of the Collaborative Study on the Genetics of Asthma (CSGA).

METHODS

Specific IgE antibody levels to the Der p crude allergen and to the purified allergens Der p 1 and Der p 2 were measured. Multipoint, nonparametric linkage analysis of 370 polymorphic markers was performed with the GENEHUNTER program.

RESULTS

The best evidence of genes controlling specific IgE response to Der p was obtained in 2 novel regions: chromosomes 2q21-q23 (P = .0033 for Caucasian subjects) and 8p23-p21 (P = .0011 for African American subjects). Three regions previously proposed as candidate regions for atopy, total IgE, or asthma also showed evidence for linkage to Der p-specific IgE responsiveness: 6p21 (P = .0064) and 13q32-q34 (P = 0.0064) in Caucasian subjects and 5q23-q33 (P = 0.0071) in African American subjects.

CONCLUSIONS

No single locus generated overwhelming evidence for linkage in terms of established criteria and guidelines for a genome-wide screening, which supports previous assertions of a heterogeneous etiology for Der p-specific IgE responsiveness. Two novel regions, 2q21-q23 and 8p23-p21, that were identified in this study merit additional study.

Genetic influences of chromosomes 5q31-q33 and 11q13 on specific IgE responsiveness to common inhaled allergens among African American families. Collaborative Study on the Genetics of Asthma (CSGA)

BACKGROUND

We have recently conducted a genome-wide screening for genes influencing Dermatophagoides pteronyssinus-specific IgE responsiveness as a part of the Collaborative Study on the Genetics of Asthma (CSGA), which showed evidence for linkage in some regions, including chromosomes 5131-q33 and 11q13 in African American families.

OBJECTIVES

To clarify relative contributions of these regions to atopy in the same African American population, we have conducted further genetic linkage studies of specific IgE responses toward common inhaled allergens.

METHODS

We studied 328 individuals in 58 African American families participating in the CSGA. Specific IgE responses toward Dermatophagoides farinae, cat, dog, American cockroach, rye grass, and Bermuda grass, as measured by skin tests, were used for multipoint linkage analysis with polymorphic markers on chromosomes 5q31-q33 and 11q13.

RESULTS

Specific IgE response toward American cockroach showed evidence for linkage to chromosomes 5q31-q33 (P = .0050) and 11q13 (P = .017). Specific IgE response toward dog showed evidence for linkage with chromosome 5q31-q33 (P = .0043). Evidence for linkage with chromosome 11q13 was obtained for specific IgE responses toward Dermatophagoides farinae (P = .012), cat (P = .035), and Bermuda grass (P = .017). The presence of a positive ST response for at least 1 of 30 common allergens showed evidence for linkage to chromosomes 5q31-q33 (P = .017) and 11q13 (P = .00058).

CONCLUSIONS

These data support that genes on both chromosomes 5q31-q33 and 11q13 confer susceptibility to upregulated IgE-mediated immune responses in this African American population. The putative genes on chromosomes 5q31-q33 and 11q13, however, showed contrasting effects on atopy, which may result from strong gene-environmental interactions.

Analysis of familial aggregation of atopic eczema and other atopic diseases by ODDS RATIO regression models

In order to determine the relative importance of genetics and the environment on the occurrence of atopic diseases, we investigated the familial aggregation of atopic eczema, allergic rhinitis, and allergic asthma in the relatives of 426 patients with atopic eczema and 628 subjects with no history of eczema (5,136 family members in total). Analyses were performed by regression models for odds ratios (OR) allowing us to estimate OR for the familial aggregation and simultaneously to adjust for other covariates. Three models were analyzed assuming that the OR i) is the same among any two members of a family, ii) depends on different familial constellations, i.e., whether the pairs are siblings, parents, or parent/sibling pairs, and iii) is not the same between the father and the children and between the mother and the children. The OR of familial aggregation for atopic eczema was 2.16 (95% confidence interval (95%-CI) 1.58-2.96) if no distinction was made between the degree of relationship. Further analyses within the members of the family showed a high OR among siblings (OR = 3.86; 95%-CI 2.10-7.09), while the OR between parents and siblings was only 1.90 (95%-CI 1.31-2.97). Only for atopic eczema was the familial aggregation between fathers and siblings (ms: OR = 2.66; fs: OR = 1.29). This can be explained by stronger maternal heritability, shared physical environment of mother and child, or environmental events that affect the fetus in utero. Since for all atopic diseases a stronger correlation was found between siblings than between siblings and parents, our study indicates that environmental factors, especially during childhood, seem to explain the recently observed increased frequencies of atopic diseases.

Association between high serum total IgE levels and D11S97 on chromosome 11q13 in Japanese subjects

The genetic linkage of atopy to chromosome 11q13 through maternally derived alleles has been previously reported. Linkage analysis in Japanese families did not confirm the existence of a major gene for atopy at this locus under the model of autosomal dominant inheritance. However, we observed a significant association between serum total IgE levels and genetic markers at this locus both in 14 Japanese atopic families and in 120 unrelated Japanese subjects. We detected eight alleles at the D11S97 locus and eight alleles in the CA/GT repeat region in the fifth intron of the Fc epsilon RI beta gene. A significantly increased frequency of the D11S97/PstI 0.96 kb allele was observed in the chromosomes of the subjects with high serum total IgE levels both in the family study (p < 0.001) and in the population study (p < 0.05). However, multipoint linkage analysis again did not show any evidence for the existence of a major gene regulating atopy on chromosome 11q13 with location scores to -35 under the model of maternal inheritance. Evidence against linkage was confirmed by the non-parametric linkage analysis, using the affected pedigree member method. Also, there was no substitution of isoleucine for leucine in the fourth transmembrane domain of Fc epsilon RI beta (Leu181), which was reported to be responsible for a subset of atopy in the British population. Therefore, the association of serum total IgE levels with chromosome 11q13 indicates that a gene or genes at this locus may contribute to the expression of high IgE levels in the Japanese population as well as in the British population, but the heterogeneity of the genetic regulation of serum total IgE levels is evident between the two populations.

Genetic analysis of atopy in three large kindreds: no evidence of linkage to D11S97

Both genetic and environmental influences have been implicated in the pathogenesis of atopic disease. A recent report suggested that a major gene providing susceptibility to atopy was transmitted in a pattern consistent with autosomal dominant inheritance and evidence was presented that places the disease locus near the D11S97 marker on human chromosome 11q. In this report, we present three large, highly characterized pedigrees in which atopy is transmitted in a pattern consistent with autosomal dominant inheritance. Genotypes at the D11S97 and HLA loci were evaluated using both lod score and sib pair methods of analysis. In these pedigrees, we reject close moderate linkage (up to 10 cM) of atopy with both D11S97 and HLA.

Lack of linkage between atopy and locus 11q13

Atopy as defined in terms of IgE responsiveness was reported to be controlled by a single gene in British families, and this concept was further supported by a significant linkage between atopy and restriction fragment length polymorphism (RFLP) detected by a DNA probe specific to chromosome 11q13. To confirm this observation in a Japanese population, segregation and linkage analyses were done in four large families. Although segregation patterns of atopy were in agreement with the pattern of autosomal dominant inheritance, there was no significant linkage between atopy and locus 11q13. Alterations in the definitions of atopy did not affect the results. These findings suggested the presence of heterogeneity in genetic elements of atopy, even though atopy may be determined mainly by a single dominant gene.

Genetic risk for asthma, allergic rhinitis, and atopic dermatitis

In order to explore the genetic risk of a child with a family history of allergies developing asthma, allergic rhinitis, or atopic dermatitis, questionnaires filled in by 6665 families were analysed. The data were collected in a population based cross sectional survey of 9-11 year old schoolchildren living in Munich and southern Bavaria. The relation between asthma, allergic rhinitis, and atopic dermatitis and the number of allergic first degree relatives, and the type of allergic disease was examined. Analyses were done separately for families with single or multiple allergic diseases. In families with one allergic parent the risk of the child developing asthma was increased by asthma in a parent, with an odds ratio (OR) of 2.6 (95% confidence interval 1.7 to 4.0) but not by parental allergic rhinitis with OR 1.0 (0.7 to 1.5) or atopic dermatitis, OR 1.0 (0.6 to 1.6). For allergic rhinitis the highest risk with OR 3.6 (2.9 to 4.6) was observed with allergic rhinitis of one parent, apparently lower for asthma of one parent, OR 2.5 (1.6 to 4.0) or atopic dermatitis, OR 1.7 (1.1 to 2.5). Children with parental atopic dermatitis had a high risk for atopic dermatitis, OR 3.4 (2.6 to 4.4), compared with children with parental asthma, OR 1.5 (1.0 to 2.2), or parental allergic rhinitis, OR 1.4 (1.1 to 1.8). Risk factors in families with combined allergies of two relatives (parents and siblings) were analysed separately for the different combinations. These results support the hypothesis that asthma, allergic rhinitis, and atopic dermatitis are multifactorial diseases brought about by various familial and environmental influences.