Using the murine cDNA clone for the beta chain of the T cell antigen receptor, we have examined four highly cytotoxic rat large granular lymphocyte (LGL) leukemia lines for the expression of unique rearrangements and mRNA transcription of the genes coding for the T cell antigen receptor. In contrast to normal rat T cells and nine rat T cell lines, the LGL leukemia lines exhibited no detectable gene rearrangements in the beta chain locus after digestion of LGL DNA by four restriction enzymes. Northern blots containing RNA from these LGL tumor lines demonstrated a low level of aberrant or nonrearranged beta chain transcription (less than 10 copies per cell) but virtually no translatable 1.3 kilobase message. These results demonstrate that LGL leukemia lines which mediate both natural killer (NK) and antibody-dependent cell-mediated cytotoxicity (ADCC) activities do not express the beta chain of the T cell receptor. The nature of the NK cell receptor for antigen remains elusive.

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