Introduction

In allergic asthma, allergen specific T lymphocytes of the CD4 subset (T helper or Th cells) control the cellular and molecular events underlying the establishment and chronic maintenance of airway inflammation that characterises the disease. The basic immunological event is the shift of allergen reactive CD4 Th lymphocytes towards a Th2 phenotype with the production of Th2 cytokines such as interleukin (IL)-4, IL-13, and IL-5. Th2 cells can support both allergen specific IgE production and eosinophil recruitment.

Recognition of allergen via the T cell receptor (TcR) provides the trigger for a specific T cell response; as any antigen, allergen is seen by Th cells as one of a few possible peptides derived from proteolytic processing. Immunogenic peptides are presented on major histocompatibility complex (MHC) molecules expressed on the membrane of antigen presenting cells. However, antigen recognition can follow such opposite events as anergy or activation of T cellsthat is, . . . [Full text of this article]