Dendritic cells overexpressing Fas-ligand induce pulmonary vasculitis in mice

Abstract

Dendritic cells (DC) genetically engineered to express Fas (CD95) ligand (FasL-DC) have been proposed as immunotherapeutic tools to induce tolerance to allografts. However, we and others recently showed that FasL-DC elicit a vigorous inflammatory response involving granulocytes and can promote Th1-type CD4+ and cytotoxic CD8+ T lymphocytes. This prompted us to evaluate the pathology induced by intravenous injection of FasL-DC in mice. We observed that FasL-DC obtained after retroviral gene transfer of bone marrow precursors derived from Fas-deficient C57Bl/6 mice induce massive pulmonary inflammation and pleuritis one day after a single intravenous injection in C57Bl/6 mice. Two months later, all mice presented granulomatous vasculitis of small to medium sized vessels, alveolar haemorrhage and pleuritis. In these lesions, apoptotic bodies were found in large number. Anti-neutrophilic cytoplasmic and anti-myeloperoxidase autoantibodies were not detected. This study documents that intravenous injection of FasL-DC causes severe lung granulomatous vasculitis. This new animal model for vasculitis is inducible, highly reproducible and shares many features with human Wegener granulomatosis. This model may be an appropriate tool to further investigate the pathogenesis of vasculitis and test new therapeutic strategies. Moreover, our findings highlight the potential severe complications of FasL-DC-based immunotherapy.

Fig. 1

(a) Heavy granulocytic inflammation (insert, ×60) predominantly localized around vessels and bronchi in the lung of C57Bl/6 mouse one day after IV injection of 1 × 10⁶ FasL-DC, H&E staining ×10. Insert: immunostaining showing a single GFP-positive FasL DC surrounded by an inflammatory infiltrate, GFP-immunostaining, ×40. (b) Slight interstitial inflammation in the lung of C57Bl/6 mouse one day after IV injection of 1 × 10⁶ control DC, H&E staining ×10. Insert: immunostaining showing a single GFP-positive control DC under the endothelium of a small vessel, GFP-immunostaining, ×40. (c) Severe pleuritis (arrow) with dense granulocyte infiltration (insert, ×60), one day after IV injection of 1 × 10⁶ FasL-DC, H&E staining ×10. (d) Extensive fibrotic pleuritis 2 months after IV injection of 1 × 10⁶ FasL-DC, H&E staining ×4. (e) Small vessel vasculitis with excentric granulomatous inflammatory reaction 2 months after IV injection of 1 × 10⁶ FasL-DC, H&E staining ×10. Arrows and insert (×60): multinucleated cells. (f) Perivascular inflammatory infiltrate predominantly composed of lymphocytes and monocytes 2 months after IV injection of 1 × 10⁶ control DC, H&E staining ×10. (g) Close-up on the inflammatory infiltrate surrounding a vessel showing destruction of the vessel wall, extensive fibrosis, numerous apoptotic bodies, and a small focus of fibrinoid necrosis (arrow), H&E staining ×40. (h) Anti-active caspase 3 immunostaining demonstrating the presence of large numbers of apoptotic cells, ×20.