IL-2/anti-IL-2 mAb immunocomplexes: A renascence of IL-2 in cancer immunotherapy?

The in vivo biological activity of IL-2 can be dramatically increased by complexing with anti-IL-2 mAb. Moreover, IL-2/anti-IL-2 mAb immunocomplexes selectively stimulate different subsets of immune cells, depending on the clone of anti-IL-2 mAb that is used. Thus, IL-2/S4B6 mAb complexes strongly stimulate CD122(high) populations, namely NK and memory CD8(+) T cells. They also intermediately stimulate T-reg cells. Conversely, IL-2/JES6.1 mAb immunocomplexes have no stimulatory activity for CD122(high) populations. However, they potently and highly selectively stimulate CD25(+) cells (i.e., T-reg and activated T cells). IL-2/S4B6 mAb immunocomplexes have also been shown to possess antitumor activity in various mouse tumor models.