Experimental autoimmune spondylodiscitis in rats.

Immunization of Lewis rats with nucleus pulposus in incomplete Freund's adjuvant, followed by in vivo injury of nucleus pulposus, induced spondylodiscitis characterized by mononuclear cell infiltration affecting the vertebral discs in 100% of experimental animals. Injury of the nucleus pulposus without prior immunization, or immunization without injury failed to induce spondylodiscitis. The nucleus pulposus, that is not antigenic normally, can lose its immunologic tolerance by the injection of syngeneic nucleus pulposus. When immunocompetent cells come into contact with the nucleus pulposus after tissue injury, an autoimmune response may appear.