The era has begun where oncology meets immunology. The recent advancement in the field of molecular biology has led to the discovery of various pathways through which cancer establishes, proliferates, grows, and disseminates. These pathways provided major insight for targeting specific molecules with the targeted therapies that show predicted responses. This targeted therapy is usually referred to as immunotherapy. These immunotherapies possess and display a unique set of toxicities mainly immunologic in nature and different from chemotherapies. This article focuses on mechanisms of immune activity of the body and various therapies available to boost these mechanisms.