Induction of lysis by T cell receptor γδ⁺/CD3⁺ T lymphocytes via CD2 requires triggering via the T11.1 epitope only

The requirements for activation of the lytic machinery through CD2 of TCRγδ⁺/CD3⁺ cells were examined, by utilizing bispecific heteroconjugates containing anti-CD2 mAb cross-linked to anti-DNP. Contrary to the CD2 activation requirements in TCRαβ⁺/CD3⁺ cells, cytotoxic activity in TCRγδ⁺/CD3⁺ clones and TCR^-/CD3^- NK cell clones can be induced by heteroconjugates containing a single anti-CD2 (OKT11.1) mAb. Activation of TCRγδ⁺/CD3⁺ cells via CD2 is independent of heteroconjugate binding to CD16 (FcγRIII), because heteroconjugates prepared from Fab fragments induced equal levels of lysis. Moreover, anti-CD16 mAb did not inhibit triggering via CD2 in TCRγδ⁺/CD3⁺ cells. In TCR^-/CD3^- NK cells, however, induction of cytotoxicity via CD2 is co-dependent on interplay with CD16. Anti-CD3 mAb blocked the anti-CD2 x anti-DNP heteroconjugate-induced cytotoxicity of TCRγδ⁺/CD3⁺ cells, indicating a functional linkage between CD2 and CD3 on these cells. We conclude that induction of lysis via CD2 shows qualitatively different activation requirements in TCRγδ⁺/CD3⁺, TCRαβ⁺/CD3⁺ CTL and TCR^-/CD3^- NK cells.