To obtain the subject new nucleic acid, capable of coding a part of a β-subunit of a mammalian T cell antigen receptor other than a mouse having a specific base sequence and useful for the production, etc. of a protein useful for the response to an extraneous antigen, diagnosis, etc. of T-cell leukemia.

This new isolated nucleic acid is 24-732 nucleotides and the nucleic acid or its complementation is capable of coding a part of a β-subunit of a mammalian T cell antigen receptor. The β-subunits of the T cell antigen receptor is coded by a polynucleotide capable of hybridizing with the nucleic acid represented by the formula or its complementation by a hybridizing method. The nucleic acid is capable of introducing an extraneous receptor site into a host and changing the response of the host to an extraneous antigen and further usable for diagnosis, etc. of T-cell leukemia. The nucleic acid is obtained by bringing a nucleic acid expressed in a T cell into contact with a nucleic acid expressed in a B cell and isolating a nonhybridizing T cell-specific nucleic acid.