Arthritis critically dependent on innate immune system players

Area of Science:

• Immunology
• Rheumatology
• Autoimmunity

Background:

• K/BxN mice serve as a model for inflammatory arthritis, mirroring rheumatoid arthritis.
• Disease pathogenesis involves autoreactivity to ubiquitous glucose-6-phosphate isomerase (GPI).
• Both T and B cells are essential for disease initiation, with anti-GPI immunoglobulins (Igs) capable of inducing arthritis independently.

Purpose of the Study:

• To elucidate the mechanisms by which arthritogenic anti-GPI Igs induce joint inflammation.
• To investigate the roles of Fc receptors and complement activation in K/BxN arthritis.
• To determine the specific complement pathway critical for disease induction.

Main Methods:

• Utilized K/BxN T cell receptor transgenic mice.
• Administered anti-GPI immunoglobulins to lymphocyte-deficient recipients.
• Investigated the involvement of Fc receptors, specifically FcgammaRIII.
• Assessed the contribution of complement activation pathways, including the alternative and classical pathways.

Main Results:

• Arthritogenic anti-GPI Igs mediate disease through Fc receptors (FcgammaRIII) and complement component C5a.
• The alternative pathway of complement activation is essential for arthritis development.
• Classical complement pathway components are dispensable for disease induction in this model.
• Mobilization of adaptive immunity can trigger excessive innate immune responses, leading to organ-specific autoimmune disease.

Conclusions:

• The alternative complement pathway and Fc receptor engagement are critical for anti-GPI antibody-induced arthritis.
• Organ-specific autoimmune diseases can arise from dysregulated innate immune responses triggered by adaptive immunity.
• Understanding these pathways offers insights into rheumatoid arthritis pathogenesis and potential therapeutic targets.