Impacts of GFP-FoxP3⁺ regulatory T cells on lupus hallmarks differ by genetic background and type of GFP knock-in

Abstract

FoxP3 reporter mice expressing green fluorescence protein (GFP) have been used as a very convenient tool to investigate the impact of regulatory T (Treg) cells on pathogenesis in autoimmune diseases. Here, we found that GFP-FoxP3⁺ knock-in (KI) mice showed alterations in the production of anti-nuclear autoantibodies (ANAs) and nephritis with different extent, depending on the presence or absence of lupus susceptibility gene locus 1 (Sle1) and KI method: contrasting with B6.Sle1.fGFP-FoxP3 mice, expressing GFP via N-terminal insertion, B6.Sle1.iGFP-FoxP3, expressing GFP via bicistronic internal ribosome entry site-driven promotion, exhibited significantly lower penetrance of serum ANA, comparing to control B6.Sle1 mice. Moreover, B6.Sle1.GFP-FoxP3⁺ mice reduced the Sle1-induced splenomegaly and B-cell expansion independently of the KI method employed, mainly by reducing the numbers of transitional 1 (T1) B cells and CD21^–CD23^– B cells, including plasmablasts and plasma cells. The absolute numbers of both splenic CD4⁺ T cells and Treg cells from B6.Sle1.GFP-FoxP3 KI mice were significantly reduced but their proportion was not changed, compared to B6.Sle1 mice. Although the glomerular basement membranes were thickened in both B6.Sle1 and B6.Sle1.iGFP-FoxP3 mice, they were thinner in B6.Sle1.fGFP-FoxP3 mice. The latter mice expressed more nephrophilic autoantibodies and deposited more complement component 3 in glomeruli compared to B6.iGFP-FoxP3 mice. FoxP3⁺ Treg cells may modulate B-cell tolerance in lupus-prone B6.Sle1 mice, presumably by modulating pathogenic, nephrophilic autoantibody production and nephritis.

Keywords:

• Regulatory T cells
• Sle1 gene locus
• anti-nuclear antibodies
• green fluorescence protein
• lupus

Acknowledgements

The authors thank Dr Alexander Rudensky (Memorial Sloan Kettering Cancer Center) for providing iGFP-FoxP3 KI mice.

Author’s contributions

H.-R. Kim had full access to all data in the study and took responsibility for the integrity of the data, as well as for the manuscript. S.-H Chang, T.-J. Kim, and H.-R. Kim designed most of the experiments, and data analysis, and manuscript preparation. Y. Kim, S.-K. Lee, J. H. Sim, Y.-J. Kim, S. J. Lee, I. J. Rhyu, K.-H. Nam, and C. Mohan participated in data acquisition and analysis.

Disclosure statement

The authors have no conflicting financial interests in this work.

Additional information

Funding

This work was supported in part by the Korea Healthcare Technology Research and Development Project, Ministry for Health, Welfare, and Family Affairs (Grant No. HI12C1633 to H.-R. Kim), by the National Research Foundation of Korea funded by the Korean government (Grants Nos. NRF-2019M3A9D5A01102794 and 2017R1A4A1015745 to H.-R. Kim), and by the Seoul National University Hospital Research Fund (Grant No. 0420120530 to H.-R. Kim).