A pilot phase I clinical trial involving 15 infusions of anti-CD3 × anti-CD20 bispecific Ab (CD20Bi)-armed anti-CD3-activated T cells (aATC) and low-dose IL-2 was conducted in three non-Hodgkin's lymphoma (NHL) patients (two high-risk and one refractory) after autologous SCT. The feasibility of T-cell expansion, safety of aATC infusions, cytotoxic immune responses and trafficking of aATC were evaluated. Three NHL patients received 15 infusions of 5 × 10(9) aATC (three infusions/week for 3 weeks and one infusion/week for 6 weeks) between days 1 and 65 after SCT with IL-2. There were no dose-limiting toxicities. Chills, fever, hypotension and malaise were the common side effects. Engraftment was delayed in one patient with a low stem cell dose. CD20Bi aATC infusions induced specific cytotoxicity directed at lymphoma targets. Endogenous peripheral blood mononuclear cells from two patients mediated anti-lymphoma cytotoxicity above preSCT background (P<0.001). (111)In labeled aATC trafficked to the lungs at 1 h and accumulated in the liver and bone marrow after 24 h. aATC infusions given over 69 days in combination with IL-2 were safe, did not inhibit engraftment, and induced endogenous cytotoxic responses directed at lymphoma targets.