Method and Compositions for Inducing Differentiation of Myeloid Derived Suppressor Cell to Treat Cancer and Infectious Diseases

A method of treating an immune suppression condition in a subject, the method comprising inducing differentiation of monocytic myeloid-derived suppressor cells (Mo-MDSCs) into non-suppressive cells by administering to the subject at least one compound that specifically binds to the extracellular domain of signal regulatory protein alpha (SIRPa) to block the interaction between the SIRPa and at least one of its ligands, wherein the immune suppression condition is selected from the group consisting of cancer, infectious disease, trauma, autoimmune disease, vaccination, chronic inflammatory disease and transplant dysfunction, and wherein said condition is improved or prevented by

A method of determining the efficacy of a compound to block the interaction between the signal regulatory protein alpha (SIRPa) and at least one of its ligands, comprising measuring the presence of non-suppressive cells that are negative MHC Class II markers and express CD80 and CD86 cell markers in a sample from a patient that received said compound, wherein the treatment is effective when the presence of said non-suppressive cell is increased in the sample in response to the compound.