Collagen antibody-induced arthritis (CAIA) is a simple mouse model of rheumatoid arthritis that can be used to address questions of pathogenic mechanisms and to screen candidate therapeutic agents. Arthritis is stimulated by the administration of a cocktail of monoclonal antibodies that are directed to conserved auto-antigenic epitopes in collagen type II, followed by endotoxin. The antibody-induced arthritis model offers several key advantages over the classic collagen-induced arthritis (CIA) model. These include rapid disease onset, high uptake rate, synchronicity, and the capacity to use genetically modified mice, such as transgenics and knockouts. This protocol takes 1-2 weeks to be completed.