Enhancement of the Anti-tumor Activity of Recombinant Interleukin-2 (rIL-2) by Immunocomplexing with an F (ab')2 Fragment of Murine Monoclonal Antibody against rIL-2

We have investigated the biological properties of an immune complex composed of recombinant interleukin-2 (rIL-2) and an F (ab')2 fragment of a monoclonal antibody against rIL-2 in mice for the induction of killer cells and anti-tumor activity, as well as the pharmacokinetic properties of the immune complex injected subcutaneous-ly into mice. The immune complex demonstrated sustained serum rIL-2 levels, with a 2.4-times longer"mean-residence-time"than free rIL-2. A more significant portion of rIL-2 was detected in lymph nodes after the subcutaneous injection of the immune complex than with rIL-2 alone. Splenic lymphocytes from mice given the immune complex showed higher killer cell activity against YAC-1 and P815 cells than those from mice given rIL-2 alone. The immune complex also exerted a more significant anti-tumor effect in a dose-dependent manner in Meth-A fibrosarcoma-bearing mice than dit rIL-2 alone.