In the spectrum of immunological diseases affecting various organs by inflammation and/or fibrosis, autoimmune reactions play an important role. Based on different studies both in humans as well as in animal models it becomes obvious that there is a broad range of pathologies that involve not only „primary“ autoimmune reactions but also other pathogenic mechanisms such as postinfectious and autoinflammatory processes. The heterogeneity within the immunological diseases may reflect the variable expression of autoinflammatory, autoimmune, and up to now unknown factors in disease development and manifestation. Based on histological and immunohistochemical examinations, IgG4-related sclerosing disease has been proposed as a novel clinicopathological entity with autoimmune phenomena but unknown etiology (chapter 1). The clarification of the etiopathological mechanisms is required to optimize prophylaxis, diagnostics and therapy. Especially, the application of novel and designer biological therapies (chapter 8) requires a better understanding of the processes that are involved in the genesis of immunological diseases. In chapter 2, some aspects of the role of epigenetic mechanisms and innate immunity in the pathogenesis of autoimmune diseases are described. Regardless of the underlying pathology, disease-associated autoantibodies are important biomarkers for the vast majority of non-organ and organ specific autoimmune diseases. However, to improve our understanding of these diseases and serological diagnostics it is necessary to search for novel autoantibodies, to further evaluate the real clinical relevance of known autoantibodies and to further develop and standardize the detection methods (chapters 3-5). Pathogenetic aspects as well as aspects of the serological diagnostics, including novel autoantibody specificities, novel methodologies and evaluation studies are presented for rheumatoid arthritis, systemic lupus erythematosus, antiphospholipid syndrome, systemic vasculitides, systemic sclerosis (chapter 6) and various organ specific diseases (chapter 7). In summary, the present volume highlights novel insights into the immune dysregulation, pathogenesis, serological diagnostics and biological therapies of autoimmune diseases.