Pathologic study of an experimental canine arthritis induced with Complete Freund's Adjuvant.

Abstract

OBJECTIVE: To describe the physiopathological features of an experimental monoarthritis in a canine model. METHODS: Pathological changes of the femorotibial joints, periarticular tissues and lymphoid organs were investigated by histology, immunohistochemistry, flow cytometry and cytokine bioassays after intra-articular administration of Complete Freund's Adjuvant in dogs. RESULTS: An edematous acute synovitis with considerable diapedesis of the neutrophilic granulocytes was observed during a primary response. This was followed by a clinical remission, although a multifocal subacute synovitis was noted with inflammatory infiltrates of mononuclear cells (macrophages > CD8 > CD4). Blood CD14 expression was upregulated and the percentage of CD8+ cells was significantly decreased. Two to four weeks post-induction, a decrease in functional impotency (secondary response) and a pyogranulomatous periarthritis with intramuscular extensions were noted. Focal cartilage erosion was due to adherent granulation tissue (CD4 > CD8 > macrophages). CONCLUSION: In this canine model, experimentally induced arthritis was mainly the result of a cell-mediated immune reaction towards a non-identified antigen.