Inhibition of non-MHC-restricted cytotoxicity by CD45 but not CD3 monoclonal antibodies in patients with large granular lymphoproliferative disease.

Nine patients with a lymphoproliferative disorder characterized by a persistent expansion of large granular lymphocytes (LGL) and an increased proportion of cells labelling with natural killer (NK) and T cell markers were identified. The six patients with an expansion of alpha beta CD3/TcR positive cells were shown to have rearranged T cell receptor (TcR) genes whereas three patients whose LGL lacked CD3/alpha beta TcR on the surface had no beta TcR rearrangement detected. Eight of the nine patients were shown to exhibit non-MHC-restricted cytotoxic activity against K562; this activity was inhibited by CD45 and CD45-associated monoclonal antibodies known to inhibit normal non-MHC-restricted cytotoxicity but not specific MHC-restricted cytotoxic T cell activity. In contrast, the CD3 monoclonal antibody OKT3 did not inhibit but redirected LGL non-MHC-restricted cytotoxicity against K562. Following modulation of the CD3 molecule, the LGL were still capable of cytolysis of K562 targets, but additional OKT3 could no longer redirect cytolysis. The data indicate that the CD3/TcR complex on the LGL clones in patients with large granular lymphoproliferative disease is not the receptor for antigen on K562 cells, although it retains functional capabilities. Thus the CD3/TcR positive subset appears to have bipotential cytotoxic characteristics involving additional unique receptors for non-MHC-restricted cytotoxicity.