Principles of cancer treatment by immunotherapy

The concept of immunotherapy as a modality to treat cancer was recognized more than a hundred years ago. High-dose interleukin-2 (IL-2) was one of the first agents to demonstrate that the host's immune system can be harnessed to treat even advanced malignancy, as was shown in a subset of patients with renal cancer and melanoma. Many tumours are immunogenic and provoke a host immune response, but this is normally not sufficient to overcome host tolerance. For decades now, researchers have tried various methods to enhance host immunological responses, such as the use of non-specific immunotherapeutic cytokines, tumour vaccines, adoptive immunotherapy and the use of monoclonal antibodies against a wide variety of molecules. This review discusses the principles of the various types of immune therapy and focuses on some of the recent developments and successes in treatment. The article concentrates on the applications of immunotherapy in solid tumours, though it has immense value in haematological cancers.