Role of TLR3 and dsRNA Hyper-Responsiveness in the Generation of the Lupus-Like Phenotype of New Zealand Black Congenic Mice

Gillian Minty¹, Nan-Hua Chang², Kieran Manion³, Yuriy Baglaenko¹, Evelyn Pau⁴ and Joan E. Wither⁵, ¹Immunology, Toronto Western Hospital, University of Toronto, Toronto, ON, Canada, ²Genetics and Development, Toronto Western Research Institute, Toronto Western Hospital, Toronto, ON, Canada, ³Immunology, University of Toronto, Toronto, ON, Canada, ⁴Toronto Western Hospital, University of Toronto, Toronto, ON, Canada, ⁵1E420/Div of Rheumatology, Toronto Western Research Institute, Toronto Western Hospital, University of Toronto, Toronto, ON, Canada

Meeting: 2013 ACR/ARHP Annual Meeting

Keywords: Lupus, mouse model and toll-like receptors

Session Information

Title: Systemic Lupus Erythematosus - Animal Models

Session Type: Abstract Submissions (ACR)

Background/Purpose: New Zealand Black (NZB) mice develop a spontaneous lupus-like autoimmune disease, similar to human systemic lupus erythematosus. Genetic mapping studies have linked loci on NZB chromosome 13 to the generation of the autoimmune phenotype. Consistent with this, congenic mice with a homozygous NZB chromosome 13 interval introgressed onto the C57BL/6 (B6) background (B6.NZBc13 (c13)) develop an autoimmune phenotype that includes: anti-chromatin, anti-ssDNA, anti-dsDNA, and anti-SmRNP autoantibody production, increased B cell activation, marginal zone B cell expansion, increased T cell activation, and dendritic cell expansion. In previous experiments these mice were found to have an apoptosis clearance defect and hyper-responsiveness to the dsRNA TLR3 ligand poly (I:C) that mapped to different areas of the interval. To examine the role of the TLR3 and poly (I:C) hyper-responsiveness in the generation of the c13 autoimmune phenotype, a TLR3 knockout was backcrossed onto the c13 genetic background.

Methods: B6.TLR3^-/- and c13.TLR3^-/-mice were aged to six months and their cellular phenotypes assessed by flow cytometry. B cell responses to TLR agonists were assessed by culturing cells for 2 days and then measuring B cell activation and TLR3 expression by flow cytometry. ELISA assays were used to quantify serum autoantibody production.

Results: Loss of TLR3 on both B6 and c13 genetic backgrounds rendered their splenocytes unresponsive to stimulation with poly (I:C), proving these mice to be true functional knockouts. De-novo B cell activation was attenuated in 6 month old c13.TLR3^-/- mice. The expanded marginal zone B cell compartment of c13 mice was also lost in knockout mice. T cell activation was unaffected in c13.TCR3^-/- mice, while there was a trend to decreased expansion of the dendritic cell population. Despite impaired B cell activation, autoantibody production was not completely abrogated in c13.TLR3^-/-mice: IgG and IgM anti-chromatin antibodies were still produced, while anti-dsDNA and -ssDNA antibody production was attenuated.

Conclusion: Relieving the dsRNA hyper-responsive sensing defect by knocking out TLR3 led to a loss of many of the altered B cell phenotypes in c13 mice but had modest effects on autoantibody production, dendritic cell expansion, and T cell activation. These findings further support the presence of at least two susceptibility loci within the c13 interval; one responsible for the dsRNA hyper-responsiveness and many of the characteristic B cell abnormalities, and the other which drives the other altered cellular phenotypes as well as chromatin autoantibody production.

Disclosure:

G. Minty,
None;

N. H. Chang,
None;

K. Manion,
None;

Y. Baglaenko,
None;

E. Pau,
None;

J. E. Wither,
None.

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