Leukocytoclasis: ultrastructural in situ nick end labeling study in anaphylactoid purpura

Early diagnosis and treatment of Leukocytoclastic Vasculitis: case report

A 46-year-old female patient presented at the emergency department of a Municipal University Hospital with necrotic lesions in lower limbs associated with wasting syndrome. She was diagnosed with leukocytoclastic vasculitis after physical examination and history-taking in a fast and cost-effective manner, using an algorithm specifically for primary vasculitis, enabling early and appropriate treatment. The good clinical outcome demonstrates the need to quickly make a definitive diagnosis and start treatment.

ANCA-associated vasculitis: is there a role for neutrophil apoptosis in autoimmunity?

The primary small vessel systemic vasculitides are disorders that target small blood vessels, inducing vessel wall inflammation, and are associated with the development of antineutrophil cytoplasmic antibodies. Multiple organs are attacked including the lungs and kidneys. Increasing knowledge of pathogenesis suggests that the antibodies activate neutrophils inappropriately, leading to endothelial and vascular damage. Cytokines, such as tumor necrosis factor, can facilitate damage by priming neutrophils and activating endothelial cells. Apoptosis of infiltrating neutrophils is also disrupted by antineutrophil cytoplasmic antibody activation. Removal of these effete cells occurs in a proinflammatory manner, promoting persistent inflammation. The autoimmune response may be promoted by aberrant phagocytosis of apoptotic neutrophils by dendritic cells. Understanding pathogenesis can help to rationalize existing therapies and indicate new approaches to therapy.

Activation, apoptosis, and clearance of neutrophils in Wegener's granulomatosis

Wegener's granulomatosis (WG) is strongly associated with the presence of antineutrophil cytoplasmic autoantibodies (ANCAs). Within WG these ANCAs are usually (80-90%) directed against the azurophilic enzyme proteinase 3, the so called PR3-ANCA. A pathophysiological role for these autoantibodies, supported by numerous in vitro and in vivo studies, is specifically based on their capacity to bind and activate neutrophils and potentially may damage vessels. In this review, the pathogenic potential of different developmental stages of the neutrophil in the pathogenesis of WG is discussed. After release from the bone marrow into the circulation, neutrophils can be primed by TNFalpha and become attached to locally activated endothelium. Once attached to the endothelium, ANCAs can fully activate these primed neutrophils. In this activation process, the degree of activation after stimulation with PR3-ANCAs associates with the level of PR3 expression on the membrane of the neutrophil. Following activation, infiltrated neutrophils become apoptotic with further membrane expression of PR3. In WG patients, clearance of apoptotic neutrophils can be disturbed due to the opsonization of PR3-expressing apoptotic neutrophils with PR3-ANCAs, thereby perpetuating inflammation by the release of proinflammatory cytokines during clearance; or it may favor autoimmunity by PR3 presentation in an inflammatory environment. Furthermore, the presence of ANCAs and the release of the vessel-related pentraxin PTX3 may lead to the persistence of late apoptotic neutrophils in tissues, thereby inducing leukocytoclastic lesions that are characteristic in patients with WG. All together, alive neutrophils as well as apoptotic neutrophils play a key role in different inflammatory phenomena seen in patients suffering from WG.

Abundance of the long pentraxin PTX3 at sites of leukocytoclastic lesions in patients with small-vessel vasculitis

OBJECTIVE

The prototypical tissue pentraxin PTX3 inhibits phagocytosis of late apoptotic polymorphonuclear leukocytes (PMNs) by macrophages. Levels of PTX3 parallel disease activity in small-vessel vasculitis. Small-vessel vasculitis is often characterized by leukocytoclasia, a phenomenon of accumulation of nuclear remnants from unscavenged PMNs in or near the vessel wall. We therefore hypothesized that PTX3 accumulates at sites of leukocytoclastic vasculitis and, as such, is a key factor for the induction of leukocytoclasis.

METHODS

We examined skin biopsy samples from 13 patients with small-vessel vasculitis and from 4 healthy and 3 inflammatory skin disease controls. Biopsy tissues, characterized histopathologically as leukocytoclastic vasculitis, were studied for the presence of PTX3 using rabbit anti-PTX3 polyclonal antibodies. Sections were scored morphometrically for leukocytoclastic infiltrates in conjunction with PTX3 staining. Morphometric scores were expressed as percentages of staining of the total tissue area.

RESULTS

Biopsy specimens from patients with leukocytoclastic vasculitis revealed an abundant up-regulation of PTX3 at sites of leukocytoclastic infiltrates. Significantly more PTX3 was found in tissues from the 13 patients with vasculitis (mean +/- SEM 48.9 +/- 6.1%) than in tissues from the 7 controls (4.5 +/- 2.7%) (P = 0.0003). PTX3 was localized around vessels, as well as spread diffusely throughout the tissue.

CONCLUSION

PTX3 is abundantly present at sites of leukocytoclastic infiltrates in patients with small-vessel vasculitis, but not in controls. Since PTX3 inhibits phagocytosis of late apoptotic PMNs by macrophages and is strongly up-regulated at sites of leukocytoclastic infiltration, PTX3 is a candidate factor in the phenomenon of leukocytoclasia in small-vessel vasculitis.