The study is designed to determine the mechanisms of pathogenesis of mycoplasmal diseases with particular emphasis on their arthritogenic potential. Laboratory animals are being used to develop models of acute and chronic arthritis. In vitro and in vivo methodology will be utilized to determine both host and agent factors which contribute to the inflammatory process. Lymphocyte activation phenomena, deposition of immune complexes and development of autoimmunity are key areas presently under study. The results of these investigations will be used to further elucidate the mechanims of acute and chronic inflammation and to define the possible role of mycoplasmas in human rheumatoid arthritis.