Isolation, flow cytometric analysis, and suppression assay of CD4+ CD25+ T-regulatory cells.

Allergy and asthma are characterized by airway hyperresponsiveness and chronic mucosal inflammation mediated by CD4+ Th2 lymphocytes and their cytokines. It is unclear why allergic individuals make a Th2-type T-cell response whereas other (non-allergic) individuals do not. Recently, attention has focused on regulatory mechanisms, such as T-regulatory cells, preventing IgE responses to allergens in nonatopic individuals. Regulatory CD4+CD25+ T cells have been described in both mice and humans. The suppressive phenotype of these cells has been associated with the expression of the forkhead transcription factor, Foxp3. It has been suggested that allergic disease may arise from an inappropriate balance between allergen activation of regulatory CD4+CD25+ T cells and effector Th2 cells or from the impairment in the suppressive activity of these so-called T-regulatory cells. The isolation of these T-regulatory cells is described in order to further our understanding of the role of these cells in allergic disease and asthma and allow us to design novel therapies.