New Therapeutic Challenges in Autoimmune Diseases

The immune system is the body’s main line of defense against invasion by infectious organisms, such as bacteria, virus, and fungi. In normal immune systems, an immune response does not occur against the self-antigen, and is called self-tolerance. Autoimmune diseases occur when body tissues are attacked by the body’s own immune system due to loss of tolerance to self-antigens (Dejaco et al., 2006). Under these conditions, body tissues are destroyed by antigen-specific cytotoxic T cells or auto-antibodies, and the accompanying inflammation can cause functional disability and morbidity. Autoimmune diseases are a heterogenous group of diseases with a wide spectrum of symptoms that affect approximately 6% of the population (Siatskas et al., 2006). They can be broadly classified as organ-specific or systemic depending on the location of the target antigen and clinical features (Sakaguchi, 2000). Common examples of systemic autoimmune diseases include systemic lupus erythematosus (SLE), rheumatoid arthritis, systemic sclerosis, ankylosing spondylitis, and polymyositis; examples of organ-specific autoimmune diseases include type 1 diabetes, Addison’s disease, Hashimoto thyroiditis, Graves’ disease, Sjögren's syndrome, vitiligo, pernicious anemia, glomerulonephritis, myasthenia gravis, Goodpasture’s syndrome, autoimmune hemolytic anemia, idiopathic thrombocytopenia purpura, and pulmonary fibrosis. The clinical features of autoimmune diseases are very different, but immunemediated mechanisms are associated with the generation of an adaptive immune response toward the target antigen (Kuby, 1994; Siatskas et al., 2006).