Immunophenotypic analysis of the inflammatory infiltrates in herniated intervertebral discs.

Study Design. The herniated portion of the lumbar disc was analyzed immunohistochemically for inflammatory infiltrates to determine their immunophenotype. Objective. To investigate the pathomechanism behind spontaneous regression of herniated discs. of Background Data. Spontaneous regression of herniated intervertebral discs has been increasingiy reported. The infiammatory response of the host has been suggested as a factor in this phenomenon. However, whether the inflammation is induced from direct chemical irotation of the nucleus pulposus material or whether it is secondary to an autoimmune response to the nucleus puiposus remains controversial. Methods. The herniated portion of the disc was collected from 38 patients who underwent surgery for lumbar disc herniation. Thin cryostat sections were made, and the extent to which infiammatory 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 tymphocyte, monocyte, macrophage, and dendritic cell markers. Results. The inflammatory infiltrates in 14 of the 38 herniated discs were subjected to immunohistochemical analysts. None of them expressed the immunophenotypic markers of the lymphocyte (CD20, CD45RO, CD4, CD8, TCRγδ), mature monocyte (CD33), or dendritic cell (CD1a, CD80, CD86, S100). Abundant infiltration of CD68-positive cells that tacked CD33 but had a variable arnount of CD11b, CD11c, and CD40 likeiy represents a process of differentiation from monocytes to macrophages, Conciusions. These findings are consistent with an immunophenotype of infiammatory responses to tissue injury or chemical irritation rather than antigen-specific immune responses. Therefore, understanding the mechanism of tissue repair is fundamentally important in the management of patients with disc hemiations.