T-CELL RECEPTOR COMPLEXES CONTAINING FC-EPSILON-RI-GAMMA HOMODIMERS IN LIEU OF CD3-ZETA AND CD3-ETA COMPONENTS - A NOVEL ISOFORM EXPRESSED ON LARGE GRANULAR LYMPHOCYTES

CD3-zeta and CD3-eta-form disulfide-linked homo- or heterodimers important in targeting partially assembled Ti-alpha-beta/CD3-gamma-delta-epsilon-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/Ti-alpha-beta+, CD4-, CD8-, CD16+, NK1.1+ mouse large granular lymphocytes (LGL), which are devoid of CD3-zeta and CD3-eta proteins. The TCRs of this subset contain homodimers of the gamma-subunit of the high affinity receptor for IgE (Fc-epsilon-RI-gamma) in lieu of CD3-zeta and/or CD3-eta-proteins. The LGL display natural killer-like activity and are cytotoxic for B cell hybridomas producing anti-CD3-epsilon 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.