Biological therapy, (sometimes also called immunotherapy, biotherapy, or biological response modifier therapy) involves a new family of agents that may be used for cancer treatment. Biological therapies use the body's immune system, either directly or indirectly, to combat cancer or to diminish the side effects that some cancer treatments can cause. The most commonly used are interferons, interleukins, stimulating factors (G-CSF, erythropoietin) and monoclonal antibodies.