T Cell Epitopes of the Timothy Grass Pollen Allergen Phl p 5 of Mice and Men and the Detection of Allergen-Specific T Cells Using Class II Ultimers

Abstract

Background: Knowledge of allergen-specific T cell epitopes is a prerequisite not only for therapeutic approaches but also for elucidating immunological mechanisms of type I allergy. Ex vivo detection of allergen-specific T cells using class II tetramer technology has become an important tool for investigating immune responses in atopic and healthy individuals. Methods: Using ³H-thymidine incorporation assays, T cell epitopes specific for the major timothy grass pollen allergen Phl p 5.0101 were mapped in 11 allergic donors and two different mouse strains. Different protocols for expansion/restimulation of T cells from the blood of allergic donors and detection of allergen-specific T cells by Class II Ultimer staining were evaluated. Results: We identified several new Phl p 5.0101 class II T cell epitopes in allergic patients and confirmed previously published ones. Additionally, we discovered the major T cell epitopes in BALB/c and C57BL/6 mice. Using a novel Class II Ultimer, we detected epitope-specific T cells expanded from the blood of an allergic donor. Conclusions: Epitope mapping of Phl p 5.0101 revealed an immunodominant epitope in BALB/c and C57BL/6 mice and an immunodominant region in humans (amino acids 259–282), which was recognized by 8 out of 11 allergic donors. Detection of Phl p 5-specific T cells was demonstrated using a Class II Ultimer specific for epitope 196–210. Successful detection of ultimer-positive T cells was strongly dependent on a resting phase after in vitro expansion.