Antitumor efficacy using NPs to deliver IL-2. C57BL/6 mice were subcutaneously injected with B16.F10 tumors and treated with either PBS, anti-CD37/IL-2 (αCD137/IL-2-Fc), liposome encapsulated αCD137/IL-2-Fc (Lipo-αCD137/IL-2-Fc), or liposome encapsulated IgG (Lipo-IgG) on days 18, 10, 12, and 14. Shown are a) tumor size, b) survival curve after systemic injections. c) Flow cytometry was used to measure the amount of CD8+ T-cells from the tumor. d) Lymphocytes from the tumor were stimulated ex vivo to determine amount of IFN-γ produced by T-cells [80].