Selective CD8 + T cells accumulate in the lungs of patients with allergic asthma after allergen bronchoprovocation

Our objective was to study whether CD4 +  or CD8 + T cells expressing particular T cell receptors (TCR) would accumulate in the lungs of patients with allergic asthma following allergen exposure. We thus analysed the TCR Vα and Vβ gene usage of CD4 + and CD8 + lung and peripheral blood lymphocytes (PBL) of eight patients with allergic asthma before and 4 days after inhalation challenge with the relevant allergen. Lung cells obtained by bronchoalveolar lavage (BAL) and paired PBL samples were analysed by flow cytometry using a panel of anti‐TCR V‐specific monoclonal antibodies that encompass ≈ 50% of the T cell repertoire. Lung‐limited T cell expansions were recorded in both the CD4 + and the CD8 + subsets. In BAL CD8 + , out of a total of 126 analyses, the number of T cell expansions increased from two to 11 after challenge, some of them dramatic. In BAL CD4 + the frequency of expansions was moderately increased already before challenge, but remained unchanged. A few expansions that tended to persist were noted in PBL CD8 + . When analysing the overall change in TCR V gene usage the largest changes were also recorded in the BAL CD8 + subset. Specific interactions between T cells and antigens may lead to an increased frequency of T cells using selected TCR V gene segments. In this study we demonstrate that following allergen bronchoprovocation in allergic asthmatic subjects, T cell expansions preferentially emerge in the lung CD8 + T cell subset.