The role of Th1-type cytokine IFN-γ in asthma is still a matter of debate: in an earlier study Krug and coworkers described an increased frequency of IFN-γ + T cells in bronchoalveolar lavage fluid from asthmatic compared with control subjects (18), and Hessel and colleagues have early demonstrated that the development of AHR is IFN-γ dependent. This evidence concerns the gene IFNG and asthma.