Immunofluorescence analysis of lymphoma-infiltrating effector cells. (A) SCID mice bearing localized Ramos lymphomas were treated with the indicated therapeutics. The figure shows representative fluorescent images of lymphoma sections obtained 24 hours after the second injection and stained for macrophages (green, F4/80) and NK cells (red, NKp46). Scale bars, 100 μm. (B) Lymphoma sections were evaluated for area percentage positive staining. Treatment with L19-IL2, but not with nontargeted rIL-2 or with a mixture of the L19-IL2 components, leads to the recruitment of NK cells and macrophages to the lymphoma site, which is especially evident in mice treated with the combination of rituximab and L19-IL2 (*P < .05; **P < .01; Student t test).