Update on laboratory studies and relationship to rheumatic and allergic diseases.

Guidelines have been presented for the optimal selection and interpretation of various laboratory tests related to rheumatologic, immunologic, and allergic disorders. The last decade has witnessed many technologic changes in the performance of screening tests for autoantibodies, and an expeditious approach to the detection of the clinically useful autoantibody system has been outlined. When both an immunofluorescent assay using an actively dividing substrate such as HEp-2 and an immunodiffusion test for precipitin autoantibodies are performed on patient sera, it is likely that most of the significant diagnostic and prognostic systems will be detected. Although exact pathogenetic roles have not been defined for all autoantibodies, it is apparent that highly specific markers for certain rheumatic diseases exist and the pertinent clinical aspects of each individual autoantibody-autoantigen system has been summarized. Why so many autoantibodies are cross-reactive with seemingly unrelated antigens is a perplexing aspect of autoimmunity, a disease process for which the necessary and sufficient conditions of development have not been defined even after decades of research. One recent hypothesis regarding the generation of diverse autoantibodies is the tenet that production is interrelated in an auto-anti-idiotypic network. Support for this hypothesis comes from the recent successful use of anti-idiotypes to DNA autoantibodies in an attempt to abrogate pathogenetic effects of target organ damage in murine models of SLE. A similar approach might be undertaken with some of the other autoantibody systems in an attempt at a novel therapy for disorders of immunoregulation.