The Characterisation of Ro/SSA and La/SSB autoantigens in exosomes derived from Hep2000 cells (#355)
Autoimmune diseases are characterized by severe immune activation against self antigens. Ro60, Ro52 and La are antigens that are commonly targeted by auto-antibodies in patients with diseases like Systemic Lupus erythematosus, Scleroderma and Sjogren’s Syndrome. Ro60 and La are protein constituents of Ribonucleoproteins which also consist of a YRNA molecule folded in a stem loop structure. It has been shown that Ro60 binds misfolded RNA in the nucleus allowing degradation. However, functions of La and Ro52 associated with Ro RNPs are not yet clarified.
Recent interest has risen in the role of exosomes in Autoimmune diseases. Exosomes are membrane vesicles which are known to be involved in antigen transfer to antigen presenting cells and direct antigen presentation to induce immune response or tolerance. It has been reported that exosomes secreted by non-neoplastic salivary gland epithelial cells contain Ro/SSA, La/SSB and other autoantigens. However, these studies are rudimentary; therefore the purpose of this study is to characterize the presence and specificity of Ro and La antigens in exosomes secreted by Hep2000 cells by using a Western blot approach.
Exosomes were collected using ExoQuick reagent from the culture media of Hep2000 cells, and separated by SDS page electrophoresis and Western Blotted using serum from patients with Sjogren ’s syndrome positive for anti Ro and Anti La antibodies. We found that exosomes secreted by Hep2000 cells contained both Ro and La autoantigens. These findings indicate that these key autoantigens are trafficked in exosomes which may facilitate their presentation by antigen presenting cells such as dendritic cells. Further fine specificity studies using affinity purified patient autoantibodies will be used to characterize the exosomal autoantigens Ro and La to increase the understanding of how these autoantigens contribute to systemic autoimmunity.