It is shown that CD25-targeted near-infrared photo-immunotherapy causes a unique, rapid and spatially selective depletion of Tregs leading to regression of the treated tumor and inducing systemic immunologic responses in untreated tumors. Based on these observations, provided are compositions and methods of killing immune suppressor cells, for example to treat cancer. Reducing the number of suppressor cells in a subject can remove suppression of effector T cells, for example, to treat cancer using the subjects own immune system. In particular examples, the method includes contacting suppressor cells having a suppressor cell surface protein with an antibody-IR700 molecule, wherein the antibody specifically binds to the suppressor cell surface protein, and in some examples the antibody does not have a functional Fc region. The cell is subsequently irradiated, such as at a wavelength of 660 to 740 nm, for example at a dose of at least 4 J cm-2.
