CD4(+) T cells engrafted with a recombinant immunoreceptor efficiently lyse target cells in a MHC antigen- and Fas-independent fashion

T cells engrafted by a recombinant immunoreceptor with predefined Ag specif icity can efficiently lyse Ag-positive target cells in a MHC Ag-independent manner. It is yet unresolved how receptor-grafted CD4(+) T cells contribut e to MHC Ag-independent target cell lysis. To address this issue, we grafte d isolated CD8(+) and CD4(+) T cells from the peripheral blood with recombi nant anti-carcinoembryonic Ag and anti-CD30 receptors, respectively. Cytoto xicity analyses revealed that grafted CD4(+) T cells exert cytolysis of Ag- positive target cells with an efficiency similar to that of grafted CD8(+) T cells. Lysis by receptor-grafted CD4(+) T cells is Ag specific and is inh ibited by blocking the target Ag or the Ag binding site of the recombinant receptor. Both Fas-sensitive and Fas-resistant target cells are lysed with equal efficiency, and lysis of Fas-sensitive target cells is not blocked by an anti-Fas ligand Ab, indicating that cytolysis by receptor-grafted CD4() T cells is independent of the Fas pathway. We conclude that cytolysis by CD4(+) T cells equipped with a recombinant immunoreceptor is MHC Ag and Fas independent and likely to be mediated by perforin present in receptor-graf ted CD4(+) T cells.