The objectives of this project are to study the natural history of systemic lupus erythematosus (SLE) in a genetically defined inbred dog colony; to isolate and identify the transmissible agent associated with the canine form of the disease; to demonstrate that this agent is the cause of canine SLE; to apply to human SLE the experimental systems used to study the transmissible agent present in canine SLE; to clarify the relationships which exist between the lupus agent and oncogenic murine RNA viruses; and to identify and characterize those viral antigenic determinants which may be common to the human, canine and murine forms of SLE. BIBLIOGRAPHIC REFERENCE: Lewis, R.M., Tannenberg, W., Smith, C. and Schwartz, R.S. Serologic evidence of C-Type viruses in systemic lupus erythematosus. Nature 252: 78-79 (1974).