The immune system functions to prevent disease. Sometimes, however, it can cause it. An overactive immune system fails to distinguish between foreign invaders and its own body constituents. As a result, it attacks a part of itself. This condition is indicative of auto immune diseases. The common characteristic of all auto immune diseases is an immune system that attacks healthy tissues, thus provoking inflammation, as well as tissue and organ damage. Autoimmunity is present to some extent in everyone, but it usually causes no harm. Auto immune diseases, however, progress to a pathogenic state that involves the whole immune system: antigens, antigen-presenting cells, T and B lymphocytes, messenger molecules, cytokines, chemokines and their receptors, and signaling and co-stimulatory molecules.

Until recently, the most common treatment for an overactive immune system has been steroids, chemotherapy and major immunosuppressants. However, such treatments carried with them serious side effects. More effective treatments target only parts of the immune system by blocking specific molecules in the inflammatory pathway. The first generation of these therapeutics, primarily directed against cytokines, are monoclonal antibodies.

The most commonly prescribed monoclonal antibodies are:

ENBREL® (etanercept)

Remicade® (infliximab)

HUMIRA® (adalimumab)

Kineret® (anakinra)

The most promising route to long term remission of autoimmune diseases comes from autologous haematopoietic stem-cell transplants (HSCTs) that 'reset' the whole immune system by replacing it with fresh cells.