Localisation of interleukin 8 in the synovial membrane, cartilage-pannus junction and chondrocytes in rheumatoid arthritis.

Interleukin-8 (IL-8) may play an important role in the development of synovitis in rheumatoid arthritis (RA), in that it is a powerful chemoattractant for neutrophils and T cells. The aim of this study was to examine the distribution of IL-8 in the synovial membrane and cartilage, from RA, osteoarthritis (OA) and normal joints. By immunohistochemical techniques, IL-8 was shown to be present in the lining layer cells in RA (87%) and in OA (62%). By contrast, only a few of the normal synovial lining layer cells (14%) contained IL-8. Deeper in the membrane the number of IL-8 positive cells decreased. Only vessels were highly positive for IL-8. At the RA cartilage-pannus junction 26% of the cells contained IL-8, whereas at the OA cartilage-pannus junction 8% of the cells were IL-8 positive (P < 0.05). Chondrocytes present in joint surface cartilage stained positive for IL-8 in an average of 20% of the cells of both RA and OA. These results provide histological evidence that IL-8 is present in the arthritic synovial tissue and cartilage, and is distributed in a manner that may form a chemotactic gradient, which favours localisation of neutrophils to the joint lumen.