Ethnic differences in asthma and associated phenotypes: collaborative study on the genetics of asthma.

BACKGROUND: In the Collaborative Study on the Genetics of Asthma, 314 families with 2584 subjects were characterized for asthma and allergy. OBJECTIVE: The purpose of this investigation was to examine clinical heterogeneity observed in asthma and allergic characteristics among 3 ethnic groups (African American, white, and Hispanic family members). METHODS: Pulmonary function parameters and asthma associated phenotypes were compared among the ethnic groups. RESULTS: In comparison with the other groups, African American sibling pairs had a significantly lower baseline FEV(1) percent of predicted (P =.0001) and a higher rate of skin test reactivity to cockroach allergen (P =.0001); Hispanic sibling pairs had significantly more skin reactivity overall (P =.001); and white sibling pairs had significantly lower total serum IgE (P <.05). In addition, there were significantly more relatives with asthma among the African American families than among the white and the Hispanic families (P =.001). CONCLUSION: Although different environmental backgrounds should be considered, these clinical differences could be due to differences in genetic susceptibility among the ethnic groups, such as those suggested by our previous genome screen.

Association and linkage of atopic dermatitis with chromosome 13q12-14 and 5q31-33 markers.

Atopic dermatitis is a chronic inflammatory skin disease that affects 10-20% of the population. Linkage of atopy, asthma, allergic rhinitis, and total serum IgE levels to several different chromosomal regions have been described extensively, but little is known about the genetic control of atopic dermatitis. We tested for the association and linkage between atopic dermatitis and five chromosomal regions: 5q31-33, 6p21.3, 12q15-24.1, 13q12-31, and 14q11.2/14q32.1-32.3. Marker analysis was performed in two Caucasian populations: (i) 192 unrelated German children with atopic dermatitis and 59 non-atopic children from a German birth cohort study (MAS'90), parental DNA was tested in 77 of 192 children with atopic dermatitis; (ii) 40 Swedish families with at least one family member with atopic dermatitis selected from the International Study of Asthma and Allergy in Children. Evidence for linkage and allelic association for atopic dermatitis was observed for markers on chromosome 13q12-14 and 5q31-33.

Physician-derived asthma diagnoses made on the basis of questionnaire data are in good agreement with interview-based diagnoses and are not affected by objective tests.

BACKGROUND: Defining the phenotype is critical for investigating the genetic etiology of asthma. As part of the Collaborative Study on the Genetics of Asthma (CSGA), the primary objective of which is to identify asthma susceptibility loci, an algorithm was designed to determine diagnoses of definite asthma, probable asthma, less than probable asthma, or no asthma. A respiratory questionnaire was designed to assist in the process of characterizing the asthma phenotype. OBJECTIVE: This study was designed to determine the validity of the CSGA algorithm for the diagnosis of asthma, to determine agreement in assessing an asthma diagnosis between the information obtained by the CSGA questionnaire versus a patient interview by a panel of specialist physicians, and to determine the degree to which objective tests would alter the questionnaire-based certainty of asthma diagnosis. METHODS: An expert panel of asthma clinicians (n = 4) indicated to what degree they were certain that a subject (n = 48) had asthma as determined by using a 6-point Likert scale based on a 20-minute interview (phase I), a review of the CSGA questionnaire (phase II), a review of the questionnaire plus skin test and peripheral blood eosinophilia data (phase III), and a review of phase III information plus pulmonary data (spirometry and methacholine-reversibility testing; IV). Intraclass correlation coefficients (ICCs) were calculated between the physicians' interpretation of the likelihood of asthma based on the information they received during each of the phases and between the CSGA algorithm and each of the phases. RESULTS: Interjudge reliability with regard to the degree of certainty with which an asthma diagnosis could be made by interview was excellent (ICC, 98; 95% confidence intervals [95% CIs], 0.87-0.99). We also found that the agreement between the physicians' interview with the patients (phase I) and the CSGA algorithm was good and at least as good with the addition of the CSGA questionnaire data and objective data (ICC, 0. 65-0.75). Good agreement was also observed between the average certainty score from the interview and the CSGA questionnaire (ICC, 92; 95% CI, 0.76-0.93), and ICCs determining the agreement on asthma diagnosis between phase I and phases III and IV, in which objective data were introduced, did not change from the ICCs comparing phase I with phase II (ICC of 0.93 [95% CI, 0.79-0.96] and ICC of 0.91 [95% CI 0.73-0.95], respectively). CONCLUSION: We conclude that the CSGA algorithm is a valid tool for which the diagnosis of asthma can be made at an acceptable level of certainty and that the CSGA questionnaire, interpreted by an asthma specialist, is a useful tool for the diagnosis of asthma in clinical or epidemiologic studies.

Dense mapping of chromosome 12q13.12-q23.3 and linkage to asthma and atopy.

BACKGROUND: Asthma is a complex disease characterized by a high prevalence of allergic diathesis and the almost ubiquitous presence of upper airway disease (eg, rhinitis). Previously, we observed linkage of asthma among Afro-Caribbean families to markers in chromosome 12q, which contains a number of genes encoding for products closely related to allergic airway inflammation and disease. OBJECTIVE: To identify susceptibility loci in chromosome 12q contributing to the genetics of upper and lower airway diseases and to expand the region to include genes encoding IFN-gamma (IFNG ) and one of the signal transducers and activators of transcription (STAT6 ), we conducted further linkage studies among 33 multiplex families. METHODS: We characterized 528 subjects from Barbados for asthma; 82% were characterized for allergic rhinitis. Two-point and multipoint linkage analysis of 22 microsatellite markers (spanning approximately 79 centimorgan) was performed. RESULTS: Affected sib-pair analysis revealed significant evidence for linkage to asthma over approximately 30 cM (P <.05 to.002), with the best evidence for linkage at a CA repeat polymorphism in the first intron of IFNG in 12q21.1 (P =.002). Evidence of linkage to allergic rhinitis was observed in the same region (D12S313, P = 0.006, and IFNGCA, P =.01, respectively). Multipoint linkage analysis also provided evidence for linkage to asthma, with the best nonparametric linkage analysis score at D12S326 (nonparametric linkage score = 3.8, P =.0008). Modest evidence for linkage to allergic rhinitis was observed next to D12S326 at D12S1052 (P =.036). CONCLUSIONS: Our findings suggest that (1) one or more loci in the chromosome 12q13. 12-q23.3 region are contributing to the expression of the clinical phenotype asthma and the strongest evidence for linkage is in a region near the gene encoding IFNG and (2) a susceptibility locus for both asthma and allergic rhinitis maps to this region.

Approaches toward the genetic analysis of complex traits: asthma and atopy.

With the challenges emerging from the analysis and interpretation of the human genome, and the specific issues pertinent to pursuing the Genome Project itself, it is truly an exciting time in the development of the biological sciences. The occasion is certainly ripe for the emergence of new concepts and ideas, as the theories of complexity, natural selection, and reductionism become integrated into a new whole. We need to learn how to approach the analyses of the complex data sets that will be generated by the Genome Project and address, more generally, the problems inherent in the analysis of the complex diseases such as asthma. Finally, we need to consider how the recent advances in genetics and genomics will affect biomedical research reaching into the next millennium and beyond.

Analysis of the three-dimensional antigenic structure of giant ragweed allergen, Amb t 5.

The ragweed allergens Amb t 5 and Amb a 5 are among the smallest inhaled protein allergens known, containing a single, immunodominant T-cell epitope. In this study we analyzed the B-cell epitope structure of Amb t 5. The three-dimensional structures of Amb t 5 and Amb a 5 have been determined by NMR spectroscopy, providing a rare opportunity to analyze three-dimensional antigenic sites. Amb t 5 residues likely to be important for antigenicity were identified by examining the surface area of Amb t 5 accessible to a probe of the size of an antibody molecule. After changing these residues to the corresponding Amb a 5 residues, recombinant proteins were purified and tested for loss of antigenic activity. Inhibition radio-immunoassays, using sera from 8 individuals who had received immunotherapy with giant ragweed extract, allowed the mutations to be divided into three groups: (1) mutations that had little or no effect on antibody binding, (2) mutations that caused a loss of antigenic activity to a different degree in different sera and (3) mutations that drastically reduced antigenic activity in all sera tested. This last set of mutations clustered in the third loop of Amb t 5, suggesting that antibody recognition of Amb t 5, like T-cell recognition, is primarily directed towards a single, immunodominant site.

Linkage analysis of Dermatophagoides pteronyssinus-specific IgE responsiveness with polymorphic markers on chromosome 6p21 (HLA-D region) in Caucasian families by the transmission/disequilibrium test. Collaborative Study on the Genetics of Asthma (CSGA).

BACKGROUND: Recently, we have obtained evidence for linkage between Der p 1-specific IgE antibodies and markers on chromosome 6p21 (HLA-D region) in a genome-wide screening in Caucasian families recruited as a part of the Collaborative Study on the Genetics of Asthma (CSGA). OBJECTIVE: Specific IgE antibodies toward different Dermatophagoides pteronyssinus (Der p) polypeptides were detected by immunoblotting analysis, and the transmission/disequilibrium test (TDT) was performed between specific IgE responsiveness toward each different Der p polypeptide and markers on chromosome 6p21 to better clarify the genetic contribution of HLA-D genes. METHODS: We studied 299 individuals in 45 Caucasian families participating in the CSGA. Serum samples from 137 individuals that showed elevated specific IgE antibodies toward the Der p crude allergen (> -0.5 log IU/mL) by ACCESS immunoassay were subjected to immunoblotting analysis. TDT was conducted between the presence of specific IgE antibodies toward each of 12 different Der p polypeptides and 4 polymorphic markers on chromosome 6p21. RESULTS: The 196-bp allele of D6S1281 and the 104-bp allele of DQCAR showed significant excess transmission to specific IgE responders toward a particular Der p polypeptide (120 kd, 55 kd, 45 kd, or 37 kd). In contrast, the 200-bp allele of D6S1281 and the 204-bp allele of D6S291 showed significantly decreased transmission to specific IgE responders toward a particular Der p polypeptide (120 kd, 90 kd, 52 kd, or 45 kd). Deviation from the expected 50% transmission in heterozygous parents was statistically significant after correcting for multiple comparisons. CONCLUSION: This study supported our previous findings that genes on chromosome 6p21 (HLA-D region) may influence the expression of Der p-specific IgE responsiveness in this Caucasian population. Our results, however, reveal the complexity of genetic regulations of Der p-specific IgE responsiveness by HLA-D genes, suggesting the strong influence of non-HLA loci and perhaps environmental factors for the development of Der p-specific IgE responsiveness.

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.

Stimulation of the high-affinity IgE receptor results in the tyrosine phosphorylation of a 60 kD protein which is associated with the protein-tyrosine kinase, Csk.

The protein tyrosine kinase Csk downregulates the activity of the Src family of kinases and has a negative effect on signal transduction through several Src kinase-associated receptors. Because the Src-family kinase Lyn plays a pivotal role in FcepsilonRI-mediated cellular activation, we examined whether Csk is involved in FcepsilonRI signaling events. Using anti-Csk antibodies and recombinant fusion proteins we detected a single tyrosine-phosphorylated protein of 60 kD (herein referred to as 'p60') that associates with the SH2 domain of Csk after stimulation of the FcepsilonRI. p60 phosphorylation reached a maximum within one minute and remained constant while the receptors were aggregated; disaggregation of the receptors resulted in rapid dephosphorylation of p60. The phosphorylation of p60 was only detected after activation by IgE and antigen and not by stimulation with PMA and/or ionomycin. Phosphorylated p60 was associated entirely with the membrane fraction of the cells. A considerable fraction of Csk was associated with the membrane in both unstimulated and stimulated cells, this fraction did not change upon activation. p60 coprecipitated with Csk from both unstimulated and FcepsilonRI stimulated cells and was phosphorylated by the immunocomplex. Total kinase activity of Csk immunoprecipitates increased upon FcepsilonRI stimulation. p60 did not react with antibodies to a number of known signaling molecules, including the recently cloned, GAP-associated protein, p62dok. Our data demonstrate that Csk associates with a membrane-anchored protein complex that is directly involved in FcepsilonRI signal transduction.

Evidence of linkage to loci for both asthma and allergic rhinitis on chromosome 12q 14.3-q24.1

As many as 80 percent of asthmatics have atopy and between 60 and 80 percent of allergic asthmatic have coexisting rhinitis. It has been proposed that asthma and allergic rhinitis are essentially the same inflammatory disease of human airways. Previously, we provided the first evidence for linkage of asthma and "high" total serum IgE concentration to chromosome 12q markers among families from Barbados and the US. To identify loci in this chromosome 12q region contributing to the distinct clinical phenotypes of asthma and allergic rhinitis, we conducted linkage analyses among 33 multiplex Barbadian families using densely-spaced microsatellite markers in the 12q14.3-q24.1 region. Maximal evidence for linkage to asthma and allergic rhinitis occurred at markers separated by 4.5 cM. D12S326 and D12S1052 = (NPL = 3.52, p = 0.001 and 1.72, p = 0.039, respectively), these two markers lie 9.13 cM downstream from IFNG. There was no evidence of linkage to either phenotype at markers flanking STAT6. These results suggest that a common gene on the long arm of chromosome 12 is important for both asthma and allergic rhinitis.(AU)

Activation of antiviral protein kinase leads to immunoglobulin E class switching in human B cells.

An epidemiologic association between viral infections and the onset of asthma and allergy has been documented. Also, evidence from animal and human studies has suggested an increase in antigen-specific immunoglobulin E (IgE) production during viral infections, and elevated levels of IgE are characteristic of human asthma and allergy. Here, we provide molecular evidence for the roles of viral infection and of activation of the antiviral protein kinase (PKR) (double-stranded-RNA [dsRNA]-activated protein kinase) in the induction of IgE class switching. The presence of dsRNA, a known component of viral infection and an activator of PKR, induced IgE class switching as detected by the expression of germ line epsilon in the human Ramos B-cell line. Furthermore, dsRNA treatment of Ramos cells resulted in the activation of PKR and in vivo activation of the NF-kappaB complex. Interestingly, infection of Ramos cells with rhinovirus (common cold virus) serotypes 14 and 16 resulted in the induction of germ line epsilon expression. To further evaluate the role of PKR in the viral induction of IgE class switching, we infected Ramos cells with two different vaccinia virus (cowpox virus) strains. Infection with wild-type vaccinia virus failed to induce germ line epsilon expression; however, a deletion mutant of vaccinia virus (VP1080) lacking the PKR-inhibitory polypeptide E3L induced the expression of germ line epsilon. Collectively, the results of our study define a common molecular mechanism underlying the role of viral infections in IgE class switching and subsequent induction of IgE-mediated disorders such as allergy and asthma.

Evidence for linkage of chromosome 12q15-q24.1 markers to high total serum IgE concentrations in children of the German Multicenter Allergy Study.

Linkage of asthma and high total serum IgE levels to chromosome 12q15-q24.1 has been recently described. To evaluate this region further in regard to total IgE responsiveness, we genotyped 52 unrelated German children with persistently "high" total serum IgE (selected from a noninterventional prospective multicenter cohort study) and their parents. We carefully defined a most extreme IgE phenotype and analyzed it as a dichotomous trait. We tested for linkage between high total IgE concentrations and nine polymorphic microsatellite markers on chromosome 12q15-q24.1 using the transmission/disequilibrium test. Evidence for linkage and allelic association for high total IgE was observed for four markers in this region. This study demonstrates the value of using extreme phenotypes in genetic analysis of a complex quantitative trait.

Approaches toward the genetic analysis of complex traits: asthma and atopy.

With the challenges emerging from the analysis and interpretation of the human genome, and the specific issues pertinent to pursuing the Genome Project itself, it is truly an exciting time in the development of the biological sciences. The occasion is certainly ripe for the emergence of new concepts and ideas, as the theories of complexity, natural selection, and reductionism become integrated into a new whole. We need to learn how to approach the analysis of the complex data sets that will be generated by the Genome Project and address, more generally, the problems inherent in the analysis of the complex diseases such as asthma. Finally, we need to consider how the recent advances in genetics and genomics will affect biomedical research into the next millennium and beyond.

Linkage analysis of asthma, allergic rhinitis and atrophy to markers on chromosome 12q in families from Barbados - abstract

Findings from numerous studies have demonstrated that there is a strong heritable component to asthma and atrophy, although the genetic pathophysiology of these traits is poorly understood. To identify loci in chromosome 12q1s-q24.1 contributing to asthma and asthma-associated traits, we conducted linkage analyses among 29 multiples Barbadian families. Sib-pair analysis of 10 polymorphic micro satellite markers in 345 full and 219 half-sib pairs from Barbados revealed evidence for linkage of certain markers with a gene(s) controlling asthma (D12S379,p=0.001; D12S311,p=0.010; D12S95,p=0.010; D12S360,p=0.018), allergic rhinitis (D12S1052,p=0.040; D12S311,p=0.005; D12S95,p0.021), total serum IgE concentration (D12S1052,p=0.016; D12S311,p=0.007; D12S360,p=0.013; D12S78,p=0.002), and specific IgE antibodies (Alec) to the storage mite Blomia tropicalis (Blot M; D12S311,p=0.006; D12S360,p=0.007; D12S78,p=0.003). Significant evidence of transmission disequilibrium was observe for certain alleles at these loci in addition to high multi allergen IgE Ab. These findings suggest that a gene(s) in the 12q 15-q24.1 region, which contains several candidate genes, including interferon-y (IFNG), is important for asthma and the associated traits of allergic rhinitis, "high" total IgE, and "high" specific IgE (AU).

Interleukin-4 (IL-4) induces phosphatidylinositol 3-kinase (p85) dephosphorylation. Implications for the role of SHP-1 in the IL-4-induced signals in human B cells.

Interleukin 4 (IL-4) is a potent cytokine produced by T cells and to a lesser extent by tumor-associated natural killer cells, basophils, and mast cells. IL-4 treatment of T cells and macrophages leads to augmentation of their cytotoxic activity. In human B cells, IL-4 is a potent stimulator of Ig class switching from IgM to IgE. The diverse biological responses induced by IL-4 are mediated through a high affinity receptor complex (IL-4R). Although a wealth of information has accumulated regarding IL-4R, the exact mechanisms of IL-4R-mediated signaling pathways in human B cells are not well defined. In an attempt to characterize the IL-4-induced signals in human B cells, we have found that IL-4 treatment induced rapid dephosphorylation of the 85-kDa regulatory subunit of phosphatidylinositol 3-kinase. To identify the protein-tyrosine phosphatase involved in the IL-4-mediated dephosphorylation, we performed Western blot analysis using monoclonal antibodies specific to protein-tyrosine phosphatases. Upon IL-4 treatment, SHP-1 was specifically translocated to the cellular membrane fraction. Furthermore, immunoprecipitation studies revealed that SHP-1 could be specifically coimmunoprecipitated with the IL-4R as well as with phosphatidylinositol 3-kinase (p85). Collectively, our observations suggest that in addition to protein phosphorylation, protein tyrosine dephosphorylation may play a role in the IL-4-induced signaling pathways.

Natural history of Hymenoptera venom sensitivity in adults.

BACKGROUND: Epidemiologic studies of Hymenoptera venom allergy in adults show a prevalence of positive venom skin test results, RASTs of 15% to 25%, or both, but most such individuals have had no systemic reactions to stings. The clinical significance and natural history of this apparently common sensitivity is uncertain. OBJECTIVE: We sought to determine the natural history of venom sensitization by observing the rate of decrease or increase in sensitivity in normal adults over 5 to 10 years. The clinical significance of these findings is related to the frequency of systemic reactions to stings during the period of observation. METHODS: Serial observations were planned in 520 volunteers and randomly selected subjects. Two follow-up visits were attempted, once after 2 to 3 years and again after 5 to 9 years, to perform repeat venom skin tests and RASTs and to review any history of interim stings and their outcomes. RESULTS: Follow-up visits were conducted with 398 subjects (375 early visits and 205 late visits). Overall, in the 398 subjects with one or more visits after a mean of 4 years, skin test responses changed from positive to negative in 44 of 98 (45%) and from negative to positive in 27 of 309 (8.7%) of the subjects. Skin test responses changed from positive to negative in 29 of 87 (33%) subjects after 2.5 years and in 43 of 54 (80%) after 6.8 years. Even when the skin test response became negative, venom-specific IgE remained positive in 11 of 29 (38%) subjects after 2.5 years and in 13 of 43 (30%) after 6.8 years. The rate of loss of sensitivity was 12% per year, similar to retrospective estimates. Skin test sensitivity to venoms disappears more rapidly in these subjects without symptoms (half-life, 4 years) than in patients receiving venom immunotherapy (half-life, 7 years). Skin test responses changed from negative to positive in 23 of 288 (8%) subjects after 2.5 years and in 9 of 151 (6%) after 6.8 years. Insect stings caused no reaction in 120 subjects with a negative skin test response, but 17% (11 of 65) of subjects with a positive skin test response (but with a negative history) had systemic reactions when stung. There was no difference between the early and late visits in the frequency of systemic reactions reported. The risk may be higher than 17% for the specific individuals (67% after 2.5 years and 20% after 6.8 years) whose positive skin test responses persist for years. This risk is lower than that of patients with a positive history (50%) but higher than that of "normal" adults or venom-treated patients (<2%). It is still not clear whether any subset of adults with a positive skin test response but a negative history can be identified, in whom the risk of systemic sting reaction would justify venom immunotherapy even before any reaction occurs. CONCLUSION: Asymptomatic venom sensitization in adults is common but transient, disappearing at the rate of 12% per year. However, the risk of a systemic reaction to a subsequent sting is significant in adults without symptoms but with positive venom skin test responses (17%) and may be higher when skin test sensitivity does persist for years.

Nucleotide sequence analysis of a complementary DNA coding for a Blomia tropicalis allergen.

Blomia tropicalis is a mite of allergenic importance in tropical and subtropical areas. A clone (Bt11a) from a B. tropicalis complementary DNA library was expressed in lambda phage and analyzed by plaque radioimmunoassay. The recombinant allergen produced by this clone was bound by IgE in 16 of 32 sera from individuals with asthma with a positive RAST response and none of 3 control sera from healthy individuals with negative RAST response to B. tropicalis. The cDNA insert was amplified by polymerase chain reaction with use of universal primers. A 582-base-pair (bp) fragment was cloned into a pCR II vector. The complete sequence of both strands was determined by using T7, SP6, and internal primers. The sequence shows a 432 bp reading frame with a 34 bp 5' untranslated region and a 116 bp 3' untranslated region with a poly A tail. Analysis of the sequence suggests that it encodes a putative signal peptide of 20 residues and a 124-residue mature protein allergen of 14,206 Da. The nucleotide and the inferred amino acid sequences did not show homology to any known sequence. No potential N-linked glycosylation site was found. The recombinant protein appears to represent a major allergen of the mite B. tropicalis.

Linkage of asthma and total serum IgE concentration to markers on chromosome 12q: evidence from Afro-Caribbean and Caucasian populations.

To identify genes potentially relevant in atopic asthma, we analyzed markers in chromosome 12q15-q24.1 for linkage to asthma and total serum IgE concentration. Sib-pair analyses of 10 markers in 345 full- and 219 half-sib pairs from 29 multiplex Afro-Caribbean families provided evidence for linkage to this region for both asthma and total serum IgE. Certain alleles at these loci showed significant evidence of transmission disequilibrium with both asthma and high IgE. Using 6 of these markers and 11 additional markers, evidence for linkage of total IgE to 12q was also found in 12 Caucasian Amish kindreds (24 nuclear families) by both sib-pair and transmission disequilibrium analyses. These findings suggest that the 12q15-q24.1 region may contain a gene(s) controlling asthma and the associated "high total IgE" trait.