Immunophenotypic analysis of the inflammatory infiltrates in herniated intervertebral discs

Study Design, The herniated portion of the lumbar disc was analyzed immunoh istochemically for inflammatory infiltrates to determine their immunophenot ype. Objective. To investigate the pathomechanism behind spontaneous regression of herniated discs. Summary of Background Data. Spontaneous regression of herniated interverteb ral discs has been increasingly reported. The inflammatory response of the host has been suggested as a factor in this phenomenon. However, whether th e inflammation is induced from direct chemical irritation of the nucleus pu lposus material or whether it is secondary to an autoimmune response to the nucleus pulposus remains controversial. Methods. The herniated portion of the disc was collected from 38 patients w ho underwent surgery for lumbar disc herniation, Thin cryostat sections wer e made, and the extent to which inflammatory cells had infiltrated the disc specimen was defined. Then the immunophenotype of cellular infiltrates in the herniated disc specimens was assessed by immunostaining using a series of antibodies for lymphocyte, monocyte, macrophage, and dendritic cell mark ers. Results. The inflammatory infiltrates in 14 of the 38 herniated discs were subjected to immunohistochemical analysis, None of them expressed the immun ophenotypic markers of the lymphocyte (CD20, CD45RO, CD4, CD8, TCR gamma de lta), mature monocyte (CD33), or dendritic cell (CD1a, CD80, CD86, S100), A bundant infiltration of CD68-positive cells that lacked CD33 but had a vari able amount of CD11b, CD11c, and CD40 likely represents a process of differ entiation from monocytes to macrophages. Conclusions, These findings are consistent with an immunophenotype of infla mmatory responses to tissue injury or chemical irritation Father than antig en-specific immune responses. Therefore, understanding the mechanism of tis sue repair is fundamentally important in the management of patients with di sc herniations.