We analysed the properties of intraepithelial lymphocytes of small intestine (SI-IEL) in KN6-transgenic (Tg) mice expressing cDNA of T-cell receptor (TCR)-gammadelta specific for the T22b molecule. While most splenic Tg TCR-gammadelta+ cells from KN6-Tg mice with H-2d/d background (Tgd/d mice) were Thy-1+ CD8alpha- CD44dull+ CD45RB+ CD69-, Tg TCR-gammadelta+ cells in SI-IEL (Tg gammadelta-IEL) were heterogeneous in the expression of Thy-1, CD8alpha and CD44 molecules and predominantly CD45RB+ CD69+. Tg gammadelta-IEL exhibited a much reduced proliferative response to the antigen (irradiated H-2b splenocytes) than splenic Tg TCR-gammadelta+ cells; the CD44+ subset, but not the CD44- subset, in Tg gammadelta-IEL responded to the antigen. Furthermore, Tg gammadelta-IEL, but not splenic Tg TCR-gammadelta+ cells, displayed cytolytic activity whether they were prepared from conventional or germ-free KN6-Tg mice. Comparative analysis of young and aged KN6-Tg mice revealed that the proportion of CD44+ cells in Tg gammadelta-IEL increased but the proliferative response of Tg gammadelta-IEL to the antigen attenuated in association with ageing. Moreover, although Tg gammadelta-IEL from Tgb/d mice contained a higher proportion of CD44+ cells than Tgd/d mice, they did not respond to the antigen. These results demonstrate that Tg TCR-gammadelta+ cells lose the ability to recognize the antigen following activation in the intestinal epithelia.