Positive and negative regulation of the Fcγ receptor–stimulating activity of RNA-containing immune complexes by RNase
Ryota Naito, Koichiro Ohmura, Shuhei Higuchi, Wataru Nakai, Masako Kohyama, Tsuneyo Mimori, Akio Morinobu, Hisashi Arase
Ryota Naito, Koichiro Ohmura, Shuhei Higuchi, Wataru Nakai, Masako Kohyama, Tsuneyo Mimori, Akio Morinobu, Hisashi Arase
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Research Article

Positive and negative regulation of the Fcγ receptor–stimulating activity of RNA-containing immune complexes by RNase

Abstract

The U1RNP complex, Ro/SSA, and La/SSB are major RNA-containing autoantigens. Immune complexes (ICs) composed of RNA-containing autoantigens and autoantibodies are suspected to be involved in the pathogenesis of some systemic autoimmune diseases. Therefore, RNase treatment, which degrades RNA in ICs, has been tested in clinical trials as a potential therapeutic agent. However, no studies to our knowledge have specifically evaluated the effect of RNase treatment on the Fcγ receptor–stimulating (FcγR-stimulating) activity of RNA-containing ICs. In this study, using a reporter system that specifically detects FcγR-stimulating capacity, we investigated the effect of RNase treatment on the FcγR-stimulating activity of RNA-containing ICs composed of autoantigens and autoantibodies from patients with systemic autoimmune diseases such as systemic lupus erythematosus. We found that RNase enhanced the FcγR-stimulating activity of Ro/SSA- and La/SSB-containing ICs, but attenuated that of the U1RNP complex–containing ICs. RNase decreased autoantibody binding to the U1RNP complex, but increased autoantibody binding to Ro/SSA and La/SSB. Our results suggest that RNase enhances FcγR activation by promoting the formation of ICs containing Ro/SSA or La/SSB. Our study provides insights into the pathophysiology of autoimmune diseases involving anti-Ro/SSA and anti-La/SSB autoantibodies, and into the therapeutic application of RNase treatment for systemic autoimmune diseases.

Authors

Ryota Naito, Koichiro Ohmura, Shuhei Higuchi, Wataru Nakai, Masako Kohyama, Tsuneyo Mimori, Akio Morinobu, Hisashi Arase

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Figure 6

Bovine pancreatic RNase also enhances the FcγRIIIA-stimulating activity of Ro60- and La-containing ICs.

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Bovine pancreatic RNase also enhances the FcγRIIIA-stimulating activity ...
The effect of bovine pancreatic RNase treatment on the FcγRIIIA-stimulating activity of Ro60- or La-containing ICs was examined. For RNase treatment, Ro60 or La and bovine pancreatic RNase were mixed in a PBS solution (50 ng of RNase per 10 ng of Ro60 or per 5 ng of La). Ro60 or La was then mixed with serum or plasma from 15 patients with SS and added to the FcγRIIIA-reporter cells. (A) The anti-Ro60 antibody–positive group (n = 11) and anti-Ro60 antibody–negative group (n = 4) are shown separately, and bovine pancreatic RNase–treated Ro60 and –untreated Ro60 were compared. (B) The anti-La antibody–positive group (n = 3) and anti-La antibody–negative group (n = 12) are shown separately, and bovine pancreatic RNase–treated La and –untreated La were compared. The vertical axis represents the change in GFP expression (%) relative to the Ro60- or La-free control for each condition, and each dot represents a single patient. The significance of differences was tested using a paired, 2-tailed t test. *P < 0.05.