Allergen-specific T cells have been thought to play a central role in the pathogenesis of asthma. It has been well documented that allergen-specific T cells derived from atopic patients are predominantly of type 2 T helper cell pattern. However, allergen-specific T cells derived in nonatopic normals are of type 1 in contrast to atopic patients. The purpose of the study was to develop and characterize both mite allergen-specific TH1 and TH2 clones from the same asthmatic child. With exogenous supplemental cytokine, both TH1 and TH2 clones from the same patient have been developed and maintained in this laboratory for more than one year. All these T cell clones showed dose dependent allergen-specific proliferative response and expressed with CD4+, CD45RA- markers. Elucidation of the origin and interaction between these two different types of T helper cells might shed light on understanding the pathogenesis of atopic diseases and the mechanisms of hyposensitization in atopic patients.