FURTHER CHARACTERIZATION OF CYTOTOXIC T-CELLS GENERATED BY SHORT-TERMCULTURE OF HUMAN PERIPHERAL-BLOOD LYMPHOCYTES WITH INTERLEUKIN-2 AND ANTI-CD3 MAB

In this study we have specifically investigated the participation of T cells in the cytotoxic activity of peripheral blood lymphocytes (PBL) activated by interleukin-2 (IL-2, 50 U/ml) alone or in combination wi th an anti CD3 mAb (BMA030, 10 ng/ml, IgG2a). Purified CD3(+) T cells, incubated in the presence of the anti-CD3 mAb for 4 days, mediated a cytotoxic activity against HL60 and U937 tumor cell lines. Several fin dings suggested the involvement of a redirected-cytotoxicity phenomeno n, since the lytic process was restricted to target cell lines bearing the high-affinity Fc gamma receptor (Fc gamma RI) and T lymphocytes s timulated by IL-2 alone did not lyse these cell Lines. Furthermore, an ti-CD3 mAb F(ab')(2) anti-CD3 IgG1 (UCHT1), phytohemagglutinin or stap hylococcal enterotoxin A did not induced a similar cytotoxic activity in T lymphocytes. The cytotoxic process occurred in the presence of a very low level of anti-CD3 antibodies (in the nanomolar range). The cy totoxic activity of T cells stimulated by IL-2 or by IL-2 + BMA030, ag ainst OVCAR-3 cells (MOv18(+) ovarian tumor cell line), was also compa red in the presence of a bispecific antibody (OC/TR, anti-CD3 x MOv18) . The stimulation by IL-2 + BMA030 induced approximately a twofold hig her cytotoxic activity than IL-2-activated T cells. This could be rela ted to the state of activation of effector cells stimulated by IL-2 BMA030, since the phenotypic analysis showed an increased proportion o f T cells expressing several activation/differentiation markers (CD25, HLA-DR, CD45RO, adhesion molecules). These findings could be applied to the design of therapeutic protocols using anti-CD3 x antitumoral bi specific antibodies.