Stuart N. Farrow

DR3 regulates negative selection during thymocyte development.

ABSTRACT DR3 (Ws1, Apo3, LARD, TRAMP, TNFSFR12) is a member of the death domain-containing tumor necrosis factor receptor (TNFR) superfamily, members of which mediate a variety of developmental events including the regulation of cell proliferation, differentiation, and apoptosis. We have investigated the in vivo role(s) of DR3 by generating mice congenitally deficient in the expression of the DR3 gene. We show that negative selection and anti-CD3-induced apoptosis are significantly impaired in DR3-null mice. In contrast, both superantigen-induced negative selection and positive selection are normal. The pre-T-cell receptor-mediated checkpoint, which is dependent on TNFR signaling, is also unaffected in DR3-deficient mice. These data reveal a nonredundant in vivo role for this TNF receptor family member in the removal of self-reactive T cells in the thymus.

Studies on the interaction between TWEAK and the death receptor WSL-1/TRAMP (DR3).

WSL‐1/TRAMP (DR3) is a member of the tumour necrosis factor (TNF) receptor superfamily which exhibits effects on NF‐κB activation and apoptosis. TWEAK, a novel TNF‐related molecule, has been proposed as the ligand for this receptor. Utilising both human and murine TWEAK ligand, it is shown that TWEAK and WSL‐1/TRAMP do not interact in an in vitro binding assay and that TWEAK binds strongly to cells that do not express WSL‐1/TRAMP on the cell surface. Biological activity of TWEAK is also observed in these cells. Finally, cells isolated from WSL‐1/TRAMP knockout mice are shown to retain their ability to interact with TWEAK. These results suggest that WSL‐1/TRAMP is not the major receptor for TWEAK

Hypoxia causes IL‐8 secretion, Charcot Leyden crystal formation, and suppression of corticosteroid‐induced apoptosis in human eosinophils

Inflamed environments are typically hypercellular, rich in pro‐inflammatory cytokines, and profoundly hypoxic. While the effects of hypoxia on neutrophil longevity and function have been widely studied, little is known about the consequences of this stimulus on eosinophils.

S34 Effects of the cyclin-dependent kinase inhibitor R-roscovitine on eosinophil survival and clearance

Background Eosinophils are pro-inflammatory cells implicated in the pathogenesis of asthma and atopy. Apoptosis has been proposed as a potential mechanism underlying the resolution of eosinophilic inflammation and studies have indicated the ability of interventions that induce human eosinophil apoptosis to promote the resolution of eosinophilic inflammation. Recently, the cyclin-dependent kinase (CDK) inhibitor R-roscovitine was shown to enhance neutrophil apoptosis and promote the resolution of neutrophilic inflammation. Aim The purpose of this study was to examine the expression of CDKs in human blood eosinophils, the effects of R-roscovitine on eosinophil survival and phagocytosis in vitro and determine whether R-roscovitine could influence eosinophilic lung inflammation in vivo. Methods Eosinophils were isolated from human peripheral blood and the effects of R-roscovitine on apoptosis, degranulation and phagocytic uptake examined in vitro. The effects of R-roscovitine on eosinophilic lung inflammation in vivo were also assessed using an ovalbumin mouse model. Results Our data demonstrate that human eosinophils express five targets for R-roscovitine: CDK1, −2, −5, −7 and −9. R-roscovitine induced eosinophil apoptosis in a time- and concentration-dependent manner but also accelerated transition to secondary necrosis as assessed by light and electron microscopy, flow cytometry and caspase activation. In addition, we report that the pro-apoptotic effect of R-roscovitine is associated with suppression of Mcl-1L expression and that the apoptotic eosinophils are phagocytosed by human monocyte derived macrophages. R-roscovitine also induced apoptosis in mouse eosinophils purified from the bone-marrow, spleen and peripheral blood. Despite this, R-roscovitine did not modulate the tissue and lumen eosinophilia characteristic of the ovalbumin mouse model of airway eosinophilia. Conclusions These data demonstrate that R-roscovitine is capable of inducing rapid apoptosis and secondary necrosis in human eosinophils but does not affect the onset or resolution of eosinophilic airway inflammation in vivo.

Death Receptor 3 regulates distinct pathological attributes of acute versus chronic murine allergic lung inflammation

Highlights • DR3 has distinctive roles in acute and chronic stages of allergic lung inflammation.• In acute lung inflammation, DR3ko mice are protected from lung cell infiltration.• In chronic lung disease, DR3 is essential for goblet cell hyperplasia.• Conclude that DR3 may be required for the development of lung pathology.