Divergent TIR signaling domains in TLR7 and TLR9 control opposing effects on systemic autoimmunity
Claire Leibler, Kayla B. Thomas, Coralie Josensi, Russell C. Levack, Shuchi Smita, Shinu John, Daniel J. Wikenheiser, Sheldon Bastacky, Sebastien Gingras, Kevin M. Nickerson, Mark J. Shlomchik
Claire Leibler, Kayla B. Thomas, Coralie Josensi, Russell C. Levack, Shuchi Smita, Shinu John, Daniel J. Wikenheiser, Sheldon Bastacky, Sebastien Gingras, Kevin M. Nickerson, Mark J. Shlomchik
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Research Article Autoimmunity Immunology

Divergent TIR signaling domains in TLR7 and TLR9 control opposing effects on systemic autoimmunity

Abstract

Toll like receptor (TLR) 7 and 9, endosomal sensors for RNA and DNA, are key mediators of autoreactivity. Although generally considered homologous, they paradoxically have opposing effects on lupus: TLR7 exacerbates the disease while TLR9 protects from it How they mediate opposing effects in autoimmunity remains undetermined. We hypothesized that differences in signaling qualities of the Toll-Interleukin 1 Receptor (TIR) domains of TLR7 and TLR9 could be responsible for their opposing effects. To test this, we introduced the TIR domain of TLR9 into the endogenous Tlr7 locus and the TLR7 TIR domain into the endogenous Tlr9 locus of mice, creating chimeric molecules termed TLR779 and TLR997. Lupus-prone MRL/lpr mice carrying Tlr779 had greatly ameliorated disease, while MRL/lpr mice carrying Tlr997 had markedly exacerbated disease compared with respective TlrWT mice. These experiments establish that TLR7 and TLR9 TIR domains have divergent properties and control disease quality, thus explaining the longstanding “TLR paradox”.

Authors

Claire Leibler, Kayla B. Thomas, Coralie Josensi, Russell C. Levack, Shuchi Smita, Shinu John, Daniel J. Wikenheiser, Sheldon Bastacky, Sebastien Gingras, Kevin M. Nickerson, Mark J. Shlomchik

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Figure 6

TLR997 and TLR999 differentially impact B cell differentiation and proliferation.

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TLR997 and TLR999 differentially impact B cell differentiation and proli...
B cells from 5–7-week-old Tlr9+/– or Tlr997 (all Tlr7–/–) MRL/lpr mice were labeled with violet proliferation dye (VPD) and cultured for 1, 2, or 3 days with CpG (1 μg/ml). (A) Representative flow cytometry plots gated on live B cells. (B) Quantification of BLIMP1hiCD138+ plasmablasts (PB) among live B cells. One-way ANOVA with Sidak’s multiple comparisons test was used to compare both genotypes. (C) BLIMP1 MFI in live B cells. Symbols indicate individual mice and error bars represent SEM. An unpaired t test was used to compare both genotypes at day 1. (D) Percentage of live-dead dye positive (LD+) and LD+VPDlo cells (which correspond to post-proliferative dead cells). For panels E–H, due to batch effects that led to differences in the overall B cell proliferation profiles, results from experiments 1 and 2 (shown in E–H) and experiments 3 and 4 (shown in Supplemental Figure 3) were analyzed separately. (E) Percentage of live B cells that divided. (F) The FlowJo Proliferation Platform analysis was used to determine the division index. (G) Cell divisions were gated based on each proliferation peak of live B cells. Division 0 corresponds to undivided cells. Y-axis shows the percentage of total live B cells within each division number at day 3 (61). (H) The percentage of PB for each division number was plotted. For panels E–H, symbols indicate mean and error bars are the SEM from n = 4 mice per genotype derived from 2 experiments. For E and F, 1-way ANOVA with Sidak’s multiple comparisons test was used. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.