TARGETING OF CYTOTOXIC T-CELLS AGAINST LEUKEMIC B-CELLS BY BISPECIFICANTIBODY (ACD3 X ACD19) DOES NOT DISTRACT THE T-CELL FROM ITS PRIMARYTARGET

Bispecific Abs (BsAb) represent a novel format of immunotherapy, recog nizing immune effector cells (e.g., T cells), on the one hand, and tar get cells (e.g., tumor cells), on the other hand. To be successful, cr oss-linking of the two cell types is necessary for effector cell activ ation and subsequent killing of the malignant target cells. We asked t he question, whether CTL that were incubated with the BsAb aCD3 x aCD1 9 and malignant B cells and activated to kill the malignant B cells we re still able to eliminate their natural target cells (e.g., virus-inf ected autologous body cells). To test this, HLA-A0201-restricted, inf luenza-specific CTL were incubated with BsAb- and HLA-A0201-positive B lymphoid tumor cells in combination with HLA-A0201-positive, virus- infected, non-B lymphoid cells as natural target cells. The results sh owed that even in the presence of BsAb and high amounts of tumor B cel ls, CTL were still capable of eliminating the virus-infected non-B lym phoid target cells; actually, CTL recognized and eliminated the homolo gous original target cells preferentially.