Immunohistological study of entheses in spondyloarthropathies: comparison in rheumatoid arthritis and osteoarthritis

Objective-To determine which inflammatory cell types are present in enthese s from patients with spondyloarthropathy (SpA) compared with patients with rheumatoid arthritis (RA) or osteoarthritis (OA). Methods-Enthesis specimens were obtained during orthopaedic procedures in e ight patients with SpA, four with RA, and three with OA. After decalcificat ion, the lymphocyte subsets (CD3, CD4, CD8, CD20) in the bone marrow compon ent of each enthesis were measured by an immunohistochemical technique. Results-Oedema and an inflammatory infiltrate were present in all the SpA s pecimens, being clearly predominant in the bone marrow component of the ent heses. The density of all cell types in the bone marrow was significantly h igher in the SpA group than in the two other groups. The cell type CD3+ sho wed the greatest difference between the SpA and RA groups, being increased fivefold in the SpA group. Within the SpA group, CD3+ cells were considerab ly more numerous than CD20+ cells-a difference fi om the RA group-and the p redominant T cells were CD8+. Conclusion Persistent oedema with an inflammatory infiltrate composed predo minantly of CD8+ cells was noted in the entheses of patients with SpA, bein g predominant in the bone marrow. These results suggest that CD8+ cells may have a key role in local inflammation in SpAs.