Autoimmune diseases are pathological conditions identified by abnormal autoimmune responses and characterized by auto-antibodies and T-cell responses to self-molecules by immune system reactivity. Some other common autoimmune disorders include rheumatoid arthritis, systemic lupus erythematosus (lupus), and vasculitis. Human autoimmune diseases (AD) occur frequently (affecting in aggregate more than 5% of the population worldwide), and impose a significant burden of morbidity and mortality on the human population. AD are defined as diseases in which immune responses to specific self-antigens contribute to the ongoing tissue damage that occurs in that disease. ADs may be either tissue-specific (eg, thyroid, β-cells of the pancreas), where unique tissue-specific antigens are targeted, or may be more systemic, in which multiple tissues are affected, and a variety of apparently ubiquitously expressed autoantigens are targeted. Women account for about 75% of the estimated 23.5 million people in America afflicted by autoimmune diseases, and autoimmune diseases constitute some of the leading causes of death and disability in women below 65 years of age. The development of autoimmune diseases depends on a combination of genetic and environmental factors. Most autoimmune diseases are thought to be polygenic, involving more than one gene. For clinicians, autoimmune diseases appear to be either systemic (eg systemic lupus erythematosus) or organspecific (eg Type 1 diabetes mellitus). This classification, although clinically useful, does not necessarily correspond to a difference in causation. A more useful division distinguishes between diseases in which there is a general alteration in the selection, regulation or death of T cells or B cells and those in which an aberrant response to a particular antigen, self or foreign, causes autoimmunity. Antigens are taken up by antigen presenting cells (APC) such as dendritic cells (DC) and processed into peptides which are loaded onto MHC molecules for presentation to T cells via clonotypic T cell receptors (TCR).