Provided herein are placenta-derived intermediate natural killer cells for use in methods of suppressing tumor cell proliferation, or treating individuals having cancer or a viral infection. The method comprises contacting the tumor cells, or administering to the individual, placental perfusate, placental perfusate cells, or natural killer cells, e.g., placenta-derived intermediate natural killer cells. The method may further comprises administering an immunomodulatory compound or thalidomide.
