A combination cancer therapy based upon catechins, the major biologically active polyphenol in plant products, including green tea extract, and one or more chemotherapeutic agents. A common complication of cancer chemotherapy is neutropenia, and in spite of advances in its prophylactic management is a major cause of risk for the development of serious microbial infections leading to increased morbidity and mortality in both humans and animals. The use of cathechins such as those found in green tea (Camellia sinensis), including but not limited to epigallocatechin gallate (EGCG) as nontoxic adjuvant to aid in the prevention of opportunistic microbial infections in patients undergoing immunosuppressive chemotherapy is a novel application. Also contemplated are methods using catechins to ameliorate the immunosuppressive effects of cancer chemotherapy by administering the compound to a patient in need thereof.