The passive transfer of high levels of anti-type II collagen antibody from mice with type II collagen-induced arthritis may transfer arthritis to syngeneic recipient animals. However, the transfer of either arthritogenic or sub-arthritogenic doses of polyclonal anti-type II collagen antibody, or non-arthritogenic monoclonal anti-type II collagen antibody may protect mice against the subsequent induction of arthritis by type II collagen. A protective effect was also observed in mice given free native type II collagen intravenously before the administration of collagen in an arthritogenic protocol.