Short-term ex vivo activation of splenocytes with anti-CD3 plus IL-2 and infusion post-BMT into mice results in in vivo expansion of effector cells with potent anti-lymphoma activity

We investigated the proliferation and therapeutic utility of anti-CD3 activated splenocytes infused into mice following BMT. Using congenic mouse strains we demonstrated that splenocytes activated briefly ex vivo with anti-CD3 plus IL-2 (T-activated killer cells or T-AK) and infused intravenously following BMT had a greater expansion in blood, spleen and BM compared with splenocytes stimulated with IL-2 alone. T-AK cells recovered from blood, spleen and BM consisted predominantly of CD8+ T cells. A single infusion of T-AK cells given on day + 1 post-syngeneic BMT and sustained in vivo with liposomal encapsulated IL-2, significantly increased survival of mice with BDL-2 lymphoma when compared with mice receiving saline and those treated with IL-2 liposomes alone. The anti-tumor effect of T-AK cells was significantly enhanced when IL-2 was given by continuous infusion compared with bolus injections. Depletion studies confirmed that the CD8+ T-AK cells were mainly responsible for the anti-tumor effect against BDL-2 lymphoma. Our findings demonstrate that brief ex vivo activation of splenocytes with anti-CD3 plus IL-2 results in in vivo proliferation of effector cells with potent anti-tumor activity following BMT.