Chapter 1 - Introduction: The Immune System, the Autoimmune State and Autoimmune Disease

Abstract

The principal role of the immune system is to confer protection on the organism against foreign invading pathogens, which can gain access to the body by different routes. The targeted (specific) immune response is generated by the combined interaction of the cellular (T lymphocytes) and humoral responses (B lymphocytes), both coordinated by the production of active substances—the cytokines. Autoimmunity is an organism's immune response against its own cells and tissues, on failure to recognize self-cells. The appearance of tolerance is a key concept in autoimmunity. The immunologic tolerance is preserved by the selection of lymphocytes in the thymus, programmed cell death (apoptosis), and cytokines. The avoidance of immunologic tolerance can lead to autoimmune disease. Autoimmune disease is any disease that results from an aberrant immune response, i.e, autoimmunity. Autoimmune diseases can result from autoantigens, polyclonal activation, aberrant expression of HLA, idiotypes and idiotypic connectivities, hormonal factors, environmental factors, and immunologic factors. There exists an association between autoimmune diseases and neoplasms. Autoimmune phenotype and various autoantibodies have been found in patients with diverse malignancies. The increased tendencies to malignancies are because of genetic factors and environmental determinants (i.e. chemotherapy). Examples of common neoplasms in autoimmune diseases include: lymphoproliferative malignancies in patients with rheumatoid arthritis, lymphomas in patients with SLE and Sjo-gren's syndrome, epithelial malignancies in patients with dermatomyositis and polymyositis, lung cancer in scleroderma and lymphomas, and thyroid papillary carcinomas in patients with autoimmune thyroid diseases.