Context
RA is a complex disease with both environmental and genetic factors implicated in the disease etiology. Animal models are useful for studying the genetics of autoimmune diseases, such as systemic lupus erythematosus (SLE) and insulin-dependent diabetes mellitus (IDDM), although a spontaneous animal model for RA is not available, at least not in rodents. Polyarthritis can be induced in animals by cartilage components such as type II collagen and proteoglycan. PGIA occurs only in genetically susceptible animals, such as BALB/c mice. When immunized with human PG, BALB/c mice develop progressive polyarthritis and later develop spondylitis. To identify the loci linked to PGIA susceptibility using whole genome screening of (BALB/c x DBA/2) F2 hybrids.