Immunological Aspects of Cardiovascular Diseases

Abstract

The immunological cardiovascular diseases are a very diverse group of clinical entities that generally are of either unknown aetiology or of unproven pathophysiology. Most of the conditions with a proven, or strongly suspected, aetiology are caused by infections, with the best examples being acute rheumatic fever and Lyme disease. However, even with these diseases, the primary pathophysiological mechanisms have not been irrefutably established. In addition to the importance of infectious agents in the immunological cardiovascular diseases, other factors have been identified that are associated with or modify these diseases. These factors include age, genetic background and coexisting inflammatory diseases. The proposed immunological mechanisms important in the immunological cardiovascular diseases include: (a) immune mimicry, in which antigens of an infectious agent crossreact with self antigens; (b) modification of self antigens by infections or other inflammatory processes; (c) introduction of self antigens to the immune system following a traumatic or inflammatory event; and (d) dysregulation of an autoimmune response. The immunological effector mechanisms include: (a) passive deposition of immunoglobulin or immune complexes in cardiovascular tissues with resulting inflammation; (b) autoantibodies that damage the cardiovascular system directly or indirectly; and (c) cell-mediated immune responses to antigens within the cardiovascular system. The clinical diagnosis of the immunological cardiovascular diseases is facilitated by clinical criteria and by selective laboratory tests in certain diseases. Laboratory tests, other than histology, do not usually provide definitive answers but serve to confirm suspected diagnoses. The vague, often systemic, symptoms associated with many of the disorders add to the clinical confusion of diagnosis. Despite the lack of clearcut aetiologies, the classification of these diseases does facilitate therapeutic decision making. This is particularly important since the prognosis of some of these conditions, such as acute rheumatic fever, Lyme disease, Wegener’s granulomatosis, systemic necrotising vasculitis and temporal arteritis, is significantly improved by treatment. Classification schemes for vasculitis remain primarily descriptive, but are useful for dividing the entities into categories with similar response to treatment. Significant progress and improvement in the treatment of the immunological cardiovascular disorders await better definition of the aetiologies and primary pathophysiological mechanisms involved.