T Cell Receptor Complexes Containing FcERI 3, Homodimers in Lieu of CD3~" and CD3v/ Components: A Novel Isoform Expressed on Large Granular Lymphocytes

CD3~" and CD37/form disulfide-linked homoor heterodimers important in targeting partially assembled Tiot-B/CD3qd~e T cell receptor (TCR) complexes to the cell surface and transducing stimulatory signals after antigen recognition. Here we identify a new TCR isoform expressed on splenic CD2 +, CD3/Tic~-/~ +, CD4-, CDS-, CD16 +, NKI.1 + mouse large granular lymphocytes (LGL), which are devoid of CD3~" and CD371 proteins. The TCRs of this subset contain homodimers of the ~/subunit of the high affinity receptor for IgE (FceRI3,) in lieu of CD3~" and/or CD3~/proteins. The LGL display natural killer-like activity and are cytotoxic for B cell hybridomas producing anti-CD3e and anti-CD16 monoclonal antibodies, demonstrating the signaling capacity of both TCR and CD16 in this cell type. These findings provide evidence for an additional level of complexity of TCR signal transduction isoforms in naturally occurring T cell subsets.