Global variations of IgE cross-reactivity in Cupressus allergy

Seasonal allergic rhinitis triggered by Cupressaceae species is a significant concern worldwide, particularly in regions such as Japan, China, Spain, and the United States.

This study investigated specific IgE responses to Cupressaceae species and the potential clinical relevance of cross-reactivity, focusing on Japanese cedar (Cryptomeria japonica [Cry j]), which is a major allergenic species in Japan.

We analyzed serum samples from 609 patients across 4 countries to measure levels of specific IgE using ImmunoCAP. We assessed IgE reactivity against Cry j extract and other Cupressaceae species, including Arizona cypress and red cedar extracts, to delineate patterns of reactivity.

Levels of specific IgE against Cry j were markedly elevated in Japanese samples; they were nearly 10-fold higher than those against other allergens. In contrast, samples from China, Spain, and the United States showed lower levels of Cry j-specific IgE, with significant levels of reactivity against Cupressus arizonica and mountain cedar (Juniperus ashei) species. Inhibition assays demonstrated that Cry j extract significantly inhibited IgE binding, particularly in Japan, suggesting dominant Cry j-specific antibodies, whereas cross-inhibition was lower in other countries. Geographic differences in pan-allergen reactivity were observed, with a notable prevalence of profilin and cross-reactive carbohydrate determinant-specific IgE in samples from the United States but minimal reactivity in samples from Japan and China.

These findings indicate notable geographic variations in specific IgE reactivity and cross-reactivity among Cupressaceae species, thus underscoring the importance of tailoring diagnostic and therapeutic approaches in allergy treatment based on region-specific allergen exposure patterns.