Identification of IgG in the canine intervertebral disc

Nucleus pulposus was taken at necropsy from five mongrel dogs and tested in an enzyme linked immunoabsorbent assay (ELISA) system designed to indicate the presence of IgG and IgM. This assay positively identified IgG. Agarose-bound Protein A was used to treat the nucleus pulposus material to extract the IgG. Repeating the ELISA using Protein A-treated nucleus pulposus showed that the ELISA was greatly diminished in activity, confirming the presence of whole molecules of IgG in nucleus pulposus. Investigators have postulated an immunologic basis for spinal pain syndromes. None to date has demonstrated IgG in the nucleus pulposus. This IgG may be a mediator by which an inflammatory response is activated which contributes to the clinical picture of chronic back and radicular pain.