Enhanced depletion of targeted cells with CD47 blockade and an immune costimulatory agonist

Methods are provided for targeting cells for depletion, including without limitation tumor cells, in a regimen comprising contacting the targeted cells with a combination of agents that modulate immunoregulatory signaling. Immunoregulatory modulating agents include (i) an agent that blockades CD47 activity; and (ii) an agent that agonizes an immune costimulatory molecule, e.g. CD137. The regimen may further comprise an agent that specifically binds to the target cell, e.g. an antibody or biologically active fragment or derivative thereof. The level of depletion of the targeted cell is enhanced relative to a regimen in which a single immunoregulatory modulating agent is used; and the effect may be synergistic relative to a regimen in which a single immunoregulatory modulating agent is used.