Mutations in the high-affinity IgE receptor beta-chain are not associated with nonresponder status

Use of Humanized RS-ATL8 Reporter System for Detection of Allergen-Specific IgE Sensitization in Human Food Allergy

Allergen-specific Immunoglobulin E (IgE) determination lies at the heart of diagnosis of sensitization to food and other allergens. In the past few years, reporter systems capable of detecting the presence of allergen-specific IgE have been developed by several labs. These rely on humanized rat basophil leukemia cell lines stably transfected with reporter genes such as firefly luciferase. In this chapter, we describe protocols for the use of the RS-ATL8 cell line (IgE cross-linking-induced luciferase expression; EXiLE) in 96-well and 384-well formats. We also describe optional treatment steps for enveloped virus and complement inactivation.

A Nonsynonymous FCER1B SNP is Associated with Risk of Developing Allergic Rhinitis and with IgE Levels

Allergic rhinitis is associated with elevated serum IgE levels. IgE response is mediated by the high-affinity IgE receptor (FcεRI), which is polymorphic. Studies analyzing the association between allergic rhinitis and FcεRI variants have been conducted with controversial results. The objective of this study is to analyze, in 1,041 individuals, the putative clinical association of allergic rhinitis with common polymorphisms in FcεRI subunits genes. These SNPs included FECR1A rs2494262, rs2427837 and rs2251746; FECR1B rs1441586, rs569108 and rs512555; FCER1G rs11587213, rs2070901 and rs11421. Statistically significant differences were observed for the FCER1B rs569108 and rs512555 polymorphisms frequencies when comparing patients with allergic rhinitis without asthma and controls. The OR (95% CI) value for the 237Gly allele (rs569108) is equal to 0.26 (0.08–0.86, P = 0.017) and for the G allele (rs512555) it is equal to 0.27 (0.08–0.88, P = 0.020). These two SNPs are linked (D’ = 1.0, LOD = 56.05). Also observed was a statistically significant trend towards lower IgE values among allergic rhinitis patients with variant alleles for both SNPs. In conclusion, in patients with allergic rhinitis without asthma, the FCER1B rs569108 and rs512555 polymorphisms are associated with increased risk of developing allergic rhinitis and with lower IgE levels.

The alpha-chain of high-affinity receptor for IgE (FcepsilonRIalpha) gene polymorphisms and serum IgE levels

BACKGROUND

The high-affinity receptor for immunoglobulin-E (IgE) (FcepsilonRI) plays a major role in the pathogenesis of allergy, but there are only two published studies on its alpha subunit (FcepsilonRIalpha) genetic variability in allergic diseases.

AIMS OF THE STUDY

Mutational screening in the region of the FcepsilonRIalpha gene promoter and the first exon with subsequent genetic variability assessment in allergic patients and a random population sample.

METHODS

Allergic subjects were individuals with asthma or urticaria. Age- and sex-matched controls were randomly selected from a large population sample. Mutational screening was performed using a single-stranded conformational polymorphism and subsequent sequencing. Detected polymorphisms were genotyped by restriction fragment length polymorphism. Total serum IgE was measured in allergic subjects and controls. Skin prick tests, blood eosinophil count and aspirin challenge test were performed only in the subjects. A subgroup of the subjects was further characterized by autologous serum skin test, histamine release test, Phadiatop and IgE antibodies against staphylococcal enterotoxins.

RESULTS

Two linked polymorphisms -344 C>T and -95 T>C were found within the FcepsilonRIalpha gene. The allele -344 T frequency was 0.45 vs 0.37 (P = 0.33), and the allele -95 C frequency was 0.26 in subjects vs 0.30 in controls (P = 0.62). Serum IgE was significantly higher in subjects homozygous for the -344T allele (TT genotype) than in those carrying the -344 C allele (CT or CC genotype; P = 0.003), but this association was not detectable in controls.

CONCLUSIONS

Our findings of genotype-related differences in IgE levels in allergic patients suggest an impact of -344 C>T but not -95 T>C gene polymorphism of FcepsilonRIalpha on total levels of IgE. The genetic variability in FcepsilonRIalpha at the -344 nucleotide of its regulatory sequence, though not related to atopy, predicts higher levels of the immunoglobulin.

Are basophil histamine release and high affinity IgE receptor expression involved in asymptomatic skin sensitization?

BACKGROUND

Immunoglobulin (Ig)E-sensitized persons with positive skin prick test, but no allergy symptoms, are classified as being asymptomatic skin sensitized (AS). The allergic type 1 disease is dependant on IgE binding to the high affinity IgE-receptor (FcepsilonRI) expressed on basophils and mast cells. However, a relationship between the AS status and FcepsilonRI has not been investigated. We aimed to characterize basophils from AS by looking at histamine release (HR) (sensitivity and reactivity) and the FcepsilonRI molecule, and compare it with nonatopic (NA) or allergic (A) persons.

METHODS

Blood was obtained from NA (n = 14), grass and/or birch A persons (n = 17) and mono-sensitized grass or birch pollen AS (n = 12). The basophil sensitivity and reactivity were examined by anti-IgE triggered HR. Surface expression of FcepsilonRI and IgE were measured by flow cytometry, FcepsilonRIalpha protein was identified using a radioimmunoassay and Western blot. mRNA coding for the classic FcepsilonRIbeta-chain and the truncated form (FcepsilonRIbetaT) were determined by real-time PCR.

RESULTS

The AS group was less reactive than NA or A persons when triggered by anti-IgE and had a significant higher number of nonresponders. However, there was no difference in sensitivity among the three groups and furthermore; the groups did not vary in FcepsilonRI- and IgE-surface expression, FcepsilonRIalpha-protein level or beta/betaT ratio.

CONCLUSION

Basophils from AS persons are less reactive and include more nonresponders than basophils from NA and A persons, but do not differ regarding the FcepsilonRI molecule.