Allo-class i-reactive cd4^-cd8^- t cell hybridomas recognize the conformational change of class i molecule resulting from the exchange of the α₃ domain

H-2K^b-reactive, interleukin (IL) 2-producing T cell hybridomas possessing neither CD8 nor CD4 molecules were employed for the study of allorecognition on interspecies hybrid antigens by T cells in the absence of an influence of these accessory molecules. Both HTB176.10 and HTB177.2 T cell hybridomas reacted with K^bK^bB7 hybrid antigens as well as K^b antigens and they produced more IL2 in response to K^b antigens than K^bK^bB7 hybrid antigens. IL2 production of these T cell hybridomas was dependent on the surface expression level of K^b molecules on stimulators. Therefore, L cells expressing almost equivalent levels of K^b or hybrid antigens were selected for further functional studies by these T cell hybridomas. They apparently produced less IL2 in response not only to interspecies hybrid antigens but also to interspecies hybrid antigens in response to K^b antigens. These results indicated that T cell hybridomas recognized the conformational change of class I molecule resulting from the exchange of the α₃ domain via their T cell receptors.