Failure of immune homeostasis -- the consequences of under and over reactivity.

The immune system is a tightly regulated network that is able to maintain a balance of immune homeostasis under normal physiological conditions. Normally, when challenged with foreign antigen, specific appropriate responses are initiated that are aimed at restoring homeostasis. However under particular circumstances, this balance is not maintained and immune responses either under or over react. Cancer is an example of a situation where the immune response can be inefficient or unresponsive, resulting in uncontrolled growth of the cancer cells. Conversely, when the immune response over-reacts, this can result in conditions such as autoimmunity or pathology following infection. Many drug therapies have been developed that aim to alleviate or prevent such immune disorders and restore immune homeostasis. This review highlights recent advances in immunotherapies, with an emphasis on specific examples in the treatment of cancer, autoimmune disease (multiple sclerosis) and viral infection (respiratory syncytial virus).