The role of Th2 type CD4 + T cells and Th2 type CD8 + T cells in asthma

Summary The cellular inflammatory responses which are seen in allergic and asthmatic diseases are viewed as being quite strongly dependent on the activities of T cells and their products. The major T cell subset involved appears to be the so‐called CD4 + Th2 subset which produces interleukin‐4 (IL‐4) and interleukin‐5 (IL‐5). In vitro and in vivo experiments have indicated that IL‐4 is a key regulator in these kinds of immune responses, not only switching B cells to IgE production, but acting on CD4 + T cells to drive their development towards a Th2 phenotype. Recent results have shown that the functional phenotype of CD8 + T cells can be switched from interferon γ production to IL‐4 and IL‐5 production by the presence of IL‐4. This could prove an especially important phenomenon since it is the production of interferon γ by CD8 T cells which is seen as necessary for protection against virus infection. This short review updates our current knowledge of how IL‐4 can act on CD4 + and CD8 + T cell subsets in in vivo models of asthma and allergic disease.