Enhancement of interleukin-2 activity by liposomes.

The present report demonstrates that liposomes increase the interleukin-2 (IL-2) dependent proliferation of cytotoxic T-lymphocyte line (CTLL) cells used for the measurement of IL-2 activity. This effect was better observed with suboptimal doses of IL-2 and low concentrations of lipids. The increased IL-2 dependent proliferation is not due to a direct effect of liposomes on CTLL cells but rather to an interaction between IL-2 and liposomes. An interaction between IL-2 and components of fetal calf serum is also demonstrated. The results indicate that liposomes may interfere with IL-2 bioassay but also show the possibility of potentiating IL-2 activity for therapeutic purposes.