Autoimmune Rheumatic Disorders: Pathogenetic and Laboratory Aspects

Abstract

Autoimmune disorders result from the attack of the immune system against self, since patients with these diseases have lost a major characteristic of the immune system, the immune tolerance (ability not to react against self). They can affect one organ (organ-specific) or many organs (systemic). The majority of autoimmune rheumatic diseases are systemic. The disorders occur in genetically predisposed individuals (associated with major histocompatibility antigens and other immunoreactive molecules) when they come across with chemical, physical, or microbial agents in the context of a particular hormonal background (majority are females) and under circumstances that create an incompetence to cope with life stressful events. The autoimmune attack can be mediated by autoantibodies, immune complexes, or T lymphocytes and can result in organ hyperfunction (e.g., hyperthyroidism), hypofunction (e.g., myasthenia gravis), or destruction of the affected organ (e.g., synovium in rheumatoid arthritis). The presence of leukocytosis and acute-phase proteins (C-reactive protein) characterizes the autoimmune disorders as inflammatory (e.g., vasculitis), while their absence as not inflammatory (e.g., systemic lupus erythematosus, SLE). B-lymphocyte hyperactivity, as attested by hyperglobulinemia and a plethora of circulating or tissue-deposited autoantibodies, is a common manifestation in the majority of autoimmune diseases, while different types of T-helper lymphocytes (Th1,Th2, and Th17) operate in different autoimmune diseases. The autoantibodies can be diagnostic (high specificity for a disease, e.g., anti-Sm for SLE), pathogenetic (e.g., DNA-anti-DNA immune complexes activate the complement cascade and induce tissue injury), or predictive for disease development (e.g., rheumatoid factors and anti-cyclic citrullinated autoantibodies).