The immune tolerance network and rheumatic disease: immune tolerance comes to the clinic

Neutrophils, neutrophil extracellular traps, and rheumatoid arthritis: An updated review for clinicians

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by the presence of autoantibodies. Research on the pathogenic mechanisms involved in systemic autoimmune diseases has largely focused on the involvement of the adaptive immune system with dysregulated responses of T and B cells. However, in recent years, there is increasing evidence of the significant role played by the innate immune system, particularly neutrophils, in these diseases, particularly in RA. Neutrophil extracellular traps (NETs) are extracellular structures composed of remodeled and concentrated chromatin with DNA, histones, and neutrophil proteins, and were first described in 2004. It has been studied that NETs may play a pathogenic role in RA and could be a source of autoantigens, increasing the immune response in the form of autoantibodies in this disease. The possible role of NETs and other markers of neutrophil activation as biomarkers of activity in RA and other immune-mediated diseases has also been studied. This article reviews the role of NETs in RA. It discusses the role of neutrophils and the latest advances in NETs, especially their involvement in autoimmune phenomena in RA. Finally, a literature review is conducted on the determination of NETs in peripheral blood and their relationship as a biomarker of RA activity, as well as their potential role in disease monitoring.

The role of neutrophil extracellular traps in rheumatic diseases

Rheumatic diseases are a collection of disorders defined by the presence of inflammation and destruction of joints and internal organs. A common feature of these diseases is the presence of autoantibodies targeting molecules commonly expressed in neutrophils. These preformed mediators are released by neutrophils but not by other immune cells such as macrophages. Neutrophils, major players in the host innate immune response, initiate a cell death mechanism termed neutrophil extracellular trap (NET) formation as a way to ensnare pathogens. NETs are also a source of released self-molecules found in rheumatic diseases. Subsequently, research on the role of NETs in the onset, progression and resolution of inflammation in rheumatic diseases has intensified. This Review has two aims. First, it aims to highlight the mechanisms required for the generation of NETs, the research landscape of which is rapidly changing. Second, it aims to discuss the role of neutrophils and NETs in systemic lupus erythematosus, vasculitis (specifically anti-neutrophil cytoplasmic autoantibody-associated vasculitis), rheumatoid arthritis and gout. Our goal is to clarify the field of NET research in rheumatic diseases in the hope of improving the therapeutic approaches utilized for these diseases.

Treatment of glomerulonephritis: will we ever have options other than steroids and cytotoxics?

Glomerulonephritis refers to a collection of primary renal disorders and those secondary to a systemic disease, all characterized by inflammation within the glomerulus. Given the underlying immunologic nature of these disorders, they are routinely treated with corticosteriods and various cytotoxic agents. Although in many instances such therapies are successful, they are associated with significant morbidity; as such, alternatives are clearly necessary. Our understanding of the pathogenesis of immunologic glomerular diseases has grown remarkably, in large part from the study of rodent disease models. Fundamental to each disorder is the development of an antigen-specific immune response followed by the effector stage of inflammation. To block the immune response, antigen-specific therapy can be used to induce tolerance, such as through the use of double-stranded DNA molecules in lupus nephritis. Since other antigen systems are less well characterized, inducing a more generalized impairment in the immune response by blocking costimulatory molecules CD40-CD154 and CD28-CD80/86 is a growing approach to treat various immunologic disorders and transplantation. To reduce glomerular inflammation, a variety of effector systems have been targeted, including complement, cytokines/chemokines, adhesion molecules, and mediators of cellular proliferation. Of these, antibodies targeting C5 in the complement system, and antibody and receptor antagonists of tumor necrosis factor-alpha (TNF-alpha) have already been used in glomerular disorders with some promise. Less specific blockade of receptor-mediated events stimulated by platelet-derived growth factors and cell cycle proteins may soon be applied to glomerulonephritis. Finally, interruption of fibrosing pathways, which lead to glomerulosclerosis and interstitial fibrosis common to the end-stage of all glomerulonephritis, is the subject of intense effort which may yield effective biologic therapies. In spite of all these advances, we still are dependent on steroids and cytotoxics to treat glomerulonephritis. To get past this, we must devote significant resources to take observations made in basic research laboratories to develop therapeutics and prove their utility in human disease.

Block and tackle: CTLA4Ig takes on lupus

Blockade of antigen nonspecific costimulatory signals is a promising approach for the treatment of autoimmune diseases including systemic lupus erythematosus (SLE). CTLA4Ig, an antagonist of the CD28/B7 costimulatory interaction, effectively prevents SLE onset in several murine models and, when used in combination with cyclophosphamide, can induce remission of active SLE nephritis. In this review we describe the known mechanisms of action of CTLA4Ig both in normal immunity and in autoimmune disease models and address issues about its activity that still need to be resolved. We discuss the preclinical use of CTLA4Ig in murine SLE models and the rationale for a clinical trial in SLE patients.

Management of lupus erythematosus: recent insights

This article reviews and cites only publications relating to the management of lupus that have appeared since 1999. The data in these publications demonstrate that preventive and proactive strategies are as important as medication in improving the quality of life and life span of the patient with lupus. The use of lasers and thalidomide represents major advances in cutaneous lupus. The first major study over 25 years using nonsteroidal anti-inflammatory drugs to manage lupus suggests benefits. Further evidence was presented showing that dehydroepiandrosterone, leflunomide, and methotrexate are effective in treating mild to moderate disease. Various iterations and modifications of traditional cyclophosphamide therapy with or without mycophenolate mofetil, cyclosporine, and azathioprine continue to be studied for treating organ-threatening disease. Intravenous gamma globulin and selective apheresis are niche therapies appropriate in a few, highly selected patients. Immunoablative doses of cyclophosphamide appear to be as effective as stem cell transplantation for serious disease resistant to conventional doses of cyclophosphamide. Twelve biologic agents have been studied in lupus since 1999, with only LJP-394 showing clear-cut, convincing efficacy.

New therapies in systemic lupus erythematosus

A new understanding of the pathogenesis of autoimmunity, the mechanisms of action of older drugs, the advent of target-specific biological therapies and pharmacogenomics has created multiple treatment options for the patient with systemic lupus erythematosus. These include topical therapies, more selective non-steroidal anti-inflammatory agents, hormonal interventions and a new generation of immune suppressives. Currently available strategies also include the use of intravenous gamma globulin, apheresis, stem-cell transplantation and antileprosy preparations alone or in combination with immune suppressives. A handful of biologicals have been studied in clinical trials. After two decades without new options for lupus patients practitioners now have a full menu of improved therapeutic options.

Testing for autoimmunity in humans

A number of the autoimmune rheumatic diseases are associated with environmental factors, drugs and chemicals. The often non-specific presentation of these diseases makes early diagnosis difficult. The availability of serological markers such as autoantibodies improves diagnostic ability when taken in context with the presenting clinical features. This review focuses on some of the major autoimmune rheumatic diseases and their associated autoantibody markers.