Immunopathological Analysis of a Mouse Model of Arthritis-Associated Scleritis and Implications for Molecular Targeted Therapy for Severe Scleritis

Scleritis involves inflammation of the sclera, which constitutes 75% of the wall of the eye. This pathology is often seen as an ocular lesion associated with systemic inflammatory diseases. Severe types of scleritis such as posterior scleritis require urgent immunosuppressive treatments, including molecularly targeted therapies to avoid permanent visual impairment. Which molecules should be selected as targets has remained unclear. To clarify the pathogenesis of scleritis and propose appropriate target molecules for therapy, we have established novel animal model of scleritis by modifying the Collagen-II Induced Arthritis (CIA) model. Immunization twice with collagen II emulsified with complete Freund's adjuvant (CFA) caused arthritis and scleritis. The clinical appearance resembled human diffuse scleritis. Histopathological analysis suggested that macrophages, plasma cells, deposition of immune complexes, and growth of blood and lymphatic vessels are involved in the pathogenesis of CIA-associated scleritis. In addition, we analysed the background diseases of posterior scleritis and responses to molecularly targeted therapies as a case series study. We inferred from both the animal model and case series study that targets should not be T cells, but factors inhibiting macrophage activity such as tumor necrosis factor (TNF) and interleukin (IL)-6, and molecules suppressing antibody-producing cells such as CD20 on B cells should be targeted by molecularly targeted therapies.