['Human T cell leukemia virus type I env-pX transgenic rats (env-pX rats) were used to investigate the pathogenesis of arthritis.', 'Phenotype of cells infiltrated into arthritic joints in env-pX rats was analyzed using flow cytometry and cell-transfer experiments were done using env-pX and wild-type WKAH rats.', 'The majority of T cells infiltrated into arthritic joints in env-pX rats exhibited a CD4 and activated phenotype. Transfer of these T cells into articular space in wild-type WKAH rats succeeded to induce arthritis similarly seen in env-pX rats. However, injection of the cells into sites other than joints did not induce inflammation. Transfer of in vitro-stimulated lymph node cells from disease-free env-pX rats into articular space did not induce arthritis in wild-type WKAH rats.'] Are articular tissues expressing the env-pX transgene required for generation of arthritogenic T cells in human T cell leukemia virus type I transgenic rats?