IMMUNOPATHOLOGY OF CHRONIC LENTIVIRUS-INDUCED ARTHRITIS

This study evaluated histopathology and mononuclear cell phenotypes in synovial lesions of chronic arthritis induced by experimental infecti on of Saanen goats with caprine arthritis-encephalitis lentivirus. His tological examination of carpal joint synovium of three infected goats with clinical arthritis revealed Progressive lesions consisting of me mbrane villus hypertrophy with extensive angiogenesis and mononuclear cell infiltration and degenerative changes of membrane villus necrosis associated with loss of vasculature and infiltrates. Changes in synov ial tissue of five age-matched infected goats without clinical arthrit is were limited to moderate synovial membrane hyperplasia also noted i n an age-matched uninfected goat. Immunohistochemistry identified CD45 R(+) CD5(-) B lymphocytes as the principal component of most Perivascu lar infiltrates ill arthritic synovium Other mononuclear cells include d perivascular CD4(+) and CD8(+) T lymphocytes and macrophages with a prominent accumulation of CD8(+) T lymphocytes at the lining surface o f inflamed villi. T lymphocytes and macrophages as well as synovial li ning cells were activated with respect to MHC class II but not for int erleukin-2 receptors. Inflamed villi also contained lymphoid aggregate s comprised of B cell germinal centers and activated T-cell mantles. B cells expressing immunoglobulin occurred around follicles and through out inflamed villi. These findings indicate that memory immune respons es that favor expansion and maturation of B cells and immunoglobulin p roduction contribute to the immunopathology of chronic arthritis.