Partial inefficiency of T cell receptors γ/δ composed of a heavy (55-kD) γ chain to mediate cell activation upon binding to specific monoclonal antibodies

Summary  We analyzed CD8+ T cell receptor (TCR) γ/δ+ (δ-TCS-1 reactive) cell clones expressing the 55-kD γ chain for their susceptibility to triggering by monoclonal antibodies (mAbs) specific for TCR or CD3 molecules. Clones were derived by limiting dilution from CD3+, WT31− FACS-purified peripheral blood populations or CD4−CD8− thymocytes (a fraction of the latter cells expressingde novo CD8 surface antigen upon culture in IL-2). Clones were screened according to their reactivity with both anti-CD8 and δ-TCS-1 mAbs. Analysis of CD3-associated molecules immunoprecipitated by anti-Leu-4 (anti-CD3) mAb under conditions which preserve the CD3/TCR association (1% digitonin) showed a predominant 55–60-kD molecule both under reducing and non-reducing conditions. All clones expressing the δ-TCS-1+ CD8+ surface phenotype derived from either thymus or peripheral blood lysed the Fcγ receptor-bearing P815 target cells in the presence of anti-CD3 mAb. On the other hand, δ-TCS-1 mAb was poorly efficient in triggering the lytic machinery of these clones, while it induced target cell lysis by δ-TCS-1+ CD8− clones.