Immunohistochemical demonstration of subclasses of inflammatory cells and active, collagen-producing fibroblasts in the synovial plicae of lumbar facet joints.

Plical tissue removed perioperatively from lumbar facet joints was studied immunohistochemically with the avidin-biotin-peroxidase complex (ABC) method for a putative presence of various subclasses of inflammatory cells and active collagen-producing fibroblasts. These methods have previously been used successfully for demonstrating specific inflammatory cells in rheumatoid arthritic synovium and cervical ligament and for studying regeneration of connective tissue, respectively. An overt inflammatory cellular response could not be demonstrated, as B lymphocytes were totally absent and no lymphocyte activation markers, either interleukin-2 receptor or immune-response-associated Ia antigens were expressed. Most of the immunoreactive cells observed were CD11b monocytes, and even these were only scattered in the connective tissue. Occasional activated collagen-producing fibroblasts were seen, suggesting in these few cases a possible regenerative response of the collagenous tissue, maybe induced by an impingement phenomenon, as such cells are not normally seen in resting connective tissue.