Modification of T-cell receptor Vβ repertoire in response to allergen stimulation in peanut allergy

Background: Peanut is one of the most common foods causing allergic reactions and is the most common cause of fatal and near-fatal food-related anaphylaxis, Little is known of the immunologic mechanisms that underlie peanut allergy. Objectives: In this study we examined clonality of the T-cell response (TCR) to peanut in MHC class II identical, peanut allergy-discordant sibling pairs. Methods: Four sibling pairs were investigated. The TCR repertoire was analyzed before and after in vitro stimulation of PBMCs with crude peanut or PHA, as control for general/nonspecific reactivity. Eighteen TCR-V beta families were examined by flow cytometry, Where significant differences in incidence of particular TCR-V beta families were observed, PCR family-specific cDNA amplification and gene scanning were performed. Results: After stimulation with peanut, no selective expansion of any TCR-V beta subpopulation was observed with now cytometry, in either the peanut-allergic or nonallergic siblings, with the exception of 1 peanut-allergic subject who demonstrated a significant increase of TCR-V beta 11(+) cells (0.34-5.9% of the total CD3(+) cells). However, gene scanning revealed predominant single-size PCR products for TCRBV11 in all peanut-allergic subjects after peanut stimulation. TCRSV11 polyclonality was observed in allergic and nonallergic subjects before peanut stimulation and in nonallergic subjects after peanut stimulation. In comparison, all subjects, before and after stimulation with peanut, showed polyclonality for TCRBV2. Conclusions: Our results argue for clonal or oligoclonal TCRs to crude peanut and indicate that changes in the TCRSV11 subpopulation are restricted to peanut-allergic subjects after stimulation with crude peanut allergen.