Abstract: The present invention relates to a composition and method useful for stimulating the immune system and for inhibiting proliferation of and inducing apoptosis in responsive cells of an animal. The present invention further relates to a composition comprising a Mycobacterium phlei deoxyribonucleic acid (M-DNA)-Mycobacterium phlei cell wall complex (MCC), wherein the Mycobacterium phlei-DNA is preserved and complexed on the Mycobacterium phlei cell wall, and a pharmaceutically acceptable carrier. MCC stimulates responsive cells of the immune system to produce cytokines and reactive oxygen species and inhibits proliferation of and induces apoptosis in responsive cells, including cancer cells, in an animal. Methods of making MCC and methods of using MCC also are disclosed.