B cell-intrinsic TLR9 expression is protective in murine lupus

Area of Science:

• Immunology
• Autoimmune Diseases
• Molecular Biology

Background:

• Toll-like receptor 9 (TLR9) regulates disease in systemic lupus erythematosus (SLE), but its specific role compared to TLR7 and MyD88 is unclear.
• Understanding TLR9's function is crucial for developing targeted SLE therapies.

Purpose of the Study:

• To investigate the cell type-specific roles of TLR9 in SLE pathogenesis.
• To determine how manipulating TLR9 expression in specific cells affects disease progression and autoantibody production.

Main Methods:

• Creation of two novel mouse alleles to selectively delete or overexpress TLR9.
• Assessment of TLR9's impact on nephritis and autoantibody levels in SLE models.
• Evaluation of TLR9's function in B cells, dendritic cells (DCs), plasmacytoid DCs, and neutrophils.

Main Results:

• Tlr9 deficiency in B cells worsened nephritis but reduced anti-nucleosome antibodies, unlinking disease severity from autoantibody production.
• Tlr9 deficiency in DCs, plasmacytoid DCs, and neutrophils did not significantly affect SLE disease.
• B cell-specific Tlr9 overexpression ameliorated nephritis, contrasting with the effects of Tlr9 deletion.

Conclusions:

• B cell-expressed TLR9 has a critical, nonredundant role in regulating lupus pathogenesis.
• Modulating or enhancing TLR9 signaling in B cells may offer a novel therapeutic strategy for SLE.