The aetiology and pathogenesis of major systemic vasculitides

Are antineutrophil cytoplasmic antibody-associated vasculitides pauci-immune?

The role of ICs in ANCA-associated vasculitides remains controversial. The ANCA-associated vasculitides are described as being pauci-immune. We hypothesize that the absence of ICs is a result of an exaggerated inflammatory response caused by the presence of ANCAs. We present evidence indicating that ICs may play a role in the initiation or relapses of the disease. The nature of the involved antigen(s) is not yet known. Possible candidates are reviewed and include ANCA antigens, AECA antigens, and staphylococcal antigens.

Pathologic features of naturally occurring juvenile polyarteritis in beagle dogs

Eighteen young Beagle dogs (eight males and 10 females), ages 6-40 months, with canine juvenile polyarteritis syndrome (CJPS), a naturally occurring vasculitis and perivasculitis of unknown etiology, were necropsied, and their tissues were examined by histopathologic and histochemical methods. The condition is characterized by recurring episodes of an acute onset of fever (> 40 C) and neck pain that persist for 3-7 days. The major histopathologic alterations were a systemic vasculitis and perivasculitis. During the febrile, painful period of CJPS, the vascular lesions ranged from a histiocytic-lymphocytic periarterial infiltration to transmural arterial inflammation with concomitant fibrinoid necrosis and vascular thrombosis. Massive periarterial accumulations of inflammatory cells were common and often extended into adjacent tissues. The small- to medium-sized muscular arteries of the heart, cranial mediastinum, and cervical spinal meninges were consistently involved. Vasculitis occasionally occurred in other organ systems. The vascular lesions in dogs examined during clinically normal periods consisted of intimal and medial fibrosis, ruptured elastic laminae, and mild perivasculitis; these lesions were probably related to previous episodes of vasculitis. Eight dogs that had experienced repeated acute episodes also developed splenic, hepatic, and renal amyloidosis. The clinical signs, laboratory abnormalities, and the vascular lesions suggest that the condition may be immune-system mediated. CJPS may serve as a naturally occurring animal model of human immune-system-mediated vasculitides such as polyarteritis nodosa, infantile polyarteritis, and Kawasaki disease.

Neurological manifestation of vasculitis: update on immunopathogenic mechanisms and clinical features

Study of the vasculitides illustrates a spectrum of interactions from physiological to pathological between the immune system and the blood-vessel wall. Endothelial cells demonstrably recruit leukocytes by both antigen-specific and antigen-nonspecific mechanisms in the systemic vasculitides. A cascade of cytokine and factors can initiate, perpetuate, and regulate the close interactions of leukocytes and the endothelium. Specific types of leukocytes (neutrophils, T lymphocytes, eosinophils) predominate in the vascular infiltrates of specific diseases. Other mural cells potentially initiate the inflammatory process; this may be particularly important in the central nervous system where regulatory systems may diminish a primary role of the endothelium in vascular inflammation. Neurological abnormalities are a prominent feature of some vasculitides and rare in others. In polyarteritis nodosa, Wegener's granulomatosis, and lymphomatoid granulomatosis neurological features may be prominent and early. The cutaneous vasculitides, hypersensitivity vasculitis, are seldom associated with neurological abnormalities. Isolated angiitis of the central nervous system is notable because it invariably targets the central nervous system and because it must be distinguished from other causes of central nervous system vasculitis, including infections and toxins. In this article we review some of the recent information adding to our knowledge of the immunopathogenic and clinical features in the vasculitides affecting the nervous system.

Diagnostic relevance of fibronectin in cryoprecipitates

Fibronectin is a known component of plasma cryoprecipitates. It is seen in cryoglobulins from patients with monoclonal gammopathies and also from rheumatoid arthritis, and patients with systemic lupus erythematosus and other connective tissue diseases. We evaluated the clinical relevance of measures of cryoprecipitable fibronectin from the sera of 88 patients with rheumatic diseases and 27 healthy controls. There were 28 patients with rheumatoid arthritis, 19 with systemic vasculitis, 5 with cutaneous vasculitis, and 36 with a systemic connective tissue disorder. We measured total and cryoprecipitable fibronectin and for comparison immunoglobulins G, A, and M and complement C3 and C4. Cryoprecipitable fibronectin was detected in 33% control sera and 42% patient sera. The mean levels were higher in the sera of patients in all diagnostic groups. The highest levels were seen in rheumatoid patients with systemic disease, systemic vasculitis, and connective tissue diseases. The presence of cryoprecipitable fibronectin was related to the clinical activity of systemic vasculitis; none of the 6 patients with clinically inactive vasculitis had detectable fibronectin in their cryoprecipitates; but it was seen in 7 to 13 cases with active vasculitis. There were only weak relationships between cryoprecipitable fibronectin and immunoglobulin and complement levels in cryoprecipitates. We conclude that routinely measuring fibronectin levels in cryoprecipitates is generally of doubtful diagnostic value. However, it appears to be a useful marker of the clinical activity of systemic vasculitis and we recommend its use in the laboratory assessment of vasculitis.