Streptococcal and staphylococcal superantigen-induced lymphocytic arteritis in a local type experimental model: comparison with acute vasculitis in the Arthus reaction

Infection and vasculitis

Vasculitis may be associated with infection, immunization or anti-microbial drugs. Infections are responsible for a number of different types of vasculitis. Conversely, patients with vasculitis may develop infections, which sometimes mimic relapse. The aim of this review is to summarize the various aspects of the inter-relationship between vasculitis and infection, and the physiopathological mechanisms involved, in light of our current knowledge from animal models. Currently, a causal relationship between infection and vasculitis has only been established in a few instances and many mechanisms remain hypothetical. This inter-relationship is further assessed from the point of view of clinical presentation and therapeutic options, based on case reports and prospective observational data.

Cutaneous Vasculitis Update: Diagnostic Criteria, Classification, Epidemiology, Etiology, Pathogenesis, Evaluation and Prognosis

Vasculitis, inflammation of the vessel wall, can result in mural destruction with hemorrhage, aneurysm formation, and infarction, or intimal-medial hyperplasia and subsequent stenosis leading to tissue ischemia. The skin, in part due to its large vascular bed, exposure to cold temperatures, and frequent presence of stasis, is involved in many distinct as well as un-named vasculitic syndromes that vary from localized and self-limited to generalized and life-threatening with multi-organ disease. To exclude mimics of vasculitis, diagnosis of cutaneous vasculitis requires biopsy confirmation where its acute signs (fibrinoid necrosis), chronic signs (endarteritis obliterans), or past signs (acellular scar of healed arteritis) must be recognized and presence of extravascular findings such as patterned fibrosis or collagenolytic granulomas noted. Although vasculitis can be classified by etiology, many cases have no identifiable cause, and a single etiologic agent can elicit several distinct clinicopathologic expressions of vasculitis. Therefore, the classification of cutaneous vasculitis is best approached morphologically by determining vessel size and principal inflammatory response. These histologic patterns roughly correlate with pathogenic mechanisms that, when coupled with direct immunofluorescent examination, anti-neutrophil cytoplasmic antibody (ANCA) status, and findings from work-up for systemic disease, allow for specific diagnosis, and ultimately, more effective therapy. Herein, we review cutaneous vasculitis focusing on diagnostic criteria, classification, epidemiology, etiology, pathogenesis, and evaluation of the cutaneous vasculitis patient.

Vasculopathy, Behçet's syndrome, and familial Mediterranean fever

Within the past year information has accumulated on the role of infections in the pathogenesis of vasculitis. Superantigens play an important role in the stimulation of the immune system. Behçet's syndrome is a vasculitis that affects children as well as adults. Recently published childhood studies highlight the importance of family history and geographic differences in this disease. Familial Mediterranean fever is a genetic disease manifesting frequently in children. Studies on the function of the mutated protein pyrin in this disease are in progress. Some researchers have proposed that pyrin is an anti-inflammatory protein. Understanding its mode of action will help us understand more of the general inflammatory pathway.

The role of superantigens in vasculitis

Multiple risk factors are involved in susceptibility to vasculitis. Inherited determinants may increase the risk but are insufficient to induce the disease. Environmental factors, such as infections, are important modulators and probably trigger the disease in most cases. One of the possible triggers may be a bacterial superantigen (SAg). SAgs may activate autoreactive T cells that mediate autoimmune vessel wall destruction. Furthermore, SAgs may activate autoreactive B cells to produce autoantibodies that are involved in the pathophysiology of vasculitis, such as antineutrophil cytoplasmic autoantibodies or anti-endothelial cell antibodies. In patients with Kawasaki disease, Wegener's granulomatosis, and infection-related forms of vasculitis, SAg-producing microorganisms have regularly been found. Activation of circulating T cells and skewing of the T-cell repertoire have been reported in most forms of vasculitis. In the past year, for the first time, patients were described in which T-cell receptor V beta expansions were documented simultaneously with the typing of the microbial SAgs, providing evidence that the observed changes in the T-cell repertoire could be caused by these bacterial SAgs. In the future, elucidation of the immunologic mechanisms by which SAgs may play a role in the pathophysiology of vasculitis will provide more effective methods for the treatment of vasculitis.