Immunostimulatory Endogenous Nucleic Acids Drive the Lesional Inflammation in Cutaneous Lupus Erythematosus.

Cutaneous lupus erythematosus (CLE) is a photosensitive autoimmune disease characterized by a strong type I IFN-associated inflammation. Keratinocytes are known to determine the interface dermatitis pattern in CLE by production of proinflammatory cytokines in the lower epidermis. These cytokines drive a cytotoxic anti-epithelial immune response resulting in keratinocytic cell death and release of endogenous nucleic acids. We hypothesized that these endogenous nucleic acids (RNA and DNA motifs) have the capacity to activate innate immune pathways in keratinocytes via pathogen recognition receptors. Gene expression analyses showed an excessive activation of innate immune response pathways with strong expression of IFN-regulated cytokines in CLE skin lesions. Cultured keratinocytes produce large amounts of these cytokines in response to stimulation of PRR with endogenous nucleic acids. UV stimulation enhances the immunogenicity of endogenous nucleic acids and induces CLE-like skin lesions in knockout mice lacking the cytosolic DNase TREX1. Our results provide evidence for a pathogenetic role of endogenous nucleic acids in CLE. They are released within the cytotoxic inflammation along the dermo-epidermal junction and have the capacity to drive the CLE-typical inflammation. UV irradiation supports this inflammation by generation of highly immunostimulatory DNA motifs (8-hydroxyguanosine). These findings explain the photosensitivity of patients with lupus and identify pathways of the innate immune system as targets for future therapies.

Effective treatment of rheumatoid arthritis-associated interstitial lung disease by B-cell targeted therapy with rituximab.

Rheumatoid arthritis- (RA-) associated interstitial lung disease (RA-ILD) is the extra-articular complication with most adverse impact on the quality of life and survival in RA patients. However, treatment options are limited and controlled studies are lacking. Here, we present the case of a 66-year-old patient suffering from severe RA-ILD, which has been successfully treated with Rituximab (RTX). After failure of conventional DMARD therapy, our patient showed sustained improvement of clinical pulmonary parameters as well as joint inflammation following B-cell depletion with RTX. The six-minute-walk test improved from 380 meters to 536 meters and the forced vital capacity from 2.49 liters to 3.49. The disease activity score could be reduced from 7.7 to 2.8. Therefore, RTX might be considered as an alternative treatment for RA-ILD in patients not responding to conventional DMARD therapy.