1125 z LOCALIZATION OF TUMOR NECROSIS FACTOR zy a IN SYNOVIAL TISSUES AND AT THE RHEUMATOID ARTHRITIS CARTILAGE-PANNUS JUNCTION IN PATIENTS WITH C. Q. CHU, M. FIELD, M. FELDMANN, and R. N. MAIN1 Using immunoaffinity-purified polyclonal anti- human recombinant tumor necrosis factor zyxwvu a (TNFa) F(ab’), fragments and immunohistochemical tech- niques, the cells that make TNFa were localized in the inflamed synovial tissue of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). Anti-TNFa antibody-stained cells were demonstrated in 9 of 11 RA and 2 of 4 OA but none of zyxwvuts 5 normal synovial membranes examined. In RA, 2644% of the lining layer cells were positive for TNFa. In the interaggregate area, 1630% of the cells contained TNFa, often in a perivascular distribution, and up to 19% of the cells in lymphoid aggregates stained for TNFa. Some endothelial cells also stained with these antibodies. In OA tissues, the TNFa- containing cells were found predominantly in the deeper layer. Cells containing TNFa were also found at the cartilage-pannus junction in all 4 RA specimens exam- ined. Double immunofluorescence analysis demon- strated that most TNFa-secreting cells in the RA syno- vial membrane expressed the monocyte/macrophage marker antigens CDllb and CD14, and a few expressed From the Division of Clinical Immunology, The Mathilda and Terence Kennedy Institute of Rheumatology, Hammersmith, and the Charing Cross Sunley Research Centre, London, England. Supported by the Arthritis and Rheumatism Council and by the Nuffield Foundation. Dr. Chu’s work is supported by the Sino-British Friendship Scholarship Scheme. C. zyxwvutsrqpon Q. Chu, MB BS: Research Fellow, Kennedy Institute of Rheumatology; M. Field, BSc, MD, MRCP: Lecturer, Kennedy Institute of Rheumatology; M. Feldmann, PhD, FRCPath: Profes- sor, Charing Cross Sunley Research Centre; R. N. Maini, FRCP: Director, Kennedy Institute of Rheumatology. Address reprint requests to M. Field, BSc, MD, MRCP, Division of Clinical Immunology, The Mathilda and Terence Ken- nedy Institute of Rheumatology, 6 Bute Gardens, Hammersmith, London W6 7DW, UK. Submitted for publication August 28, 1990; accepted in revised form April 8, 1991. the T cell marker CD3. Our findings provide histologic evidence that TNFa is locally produced in the lining and deeper layers of the synovium by cells of the monocyte/ macrophage lineage, supporting its role in inflamma- tion. Further, our findings demonstrate that TNFa is produced by cells at the cartilage-pannus junction, which could affect chondrocyte metabolism, leading to the cartilage degradation in RA. Human tumor necrosis factor a (TNFa) is a 17-kd nonglycosylated protein (1) originally defined by its ability to induce hemorrhagic tumor necrosis in animals (2). However, TNFa can also act on other cells (3) that regulate the immune and inflammatory responses, thereby causing damage to connective tis- sue. These properties suggest that TNFa may contrib- ute to the pathogenesis of the synovitis and joint destruction in rheumatic diseases by stimulating fibro- blast growth (4), inducing prostaglandin E, and colla- genase release from synovial cells zyx (5), inducing resorp- tion of bone and cartilage (6,7), and inhibiting synthesis of proteoglycan in cartilage (8). In addition, it activates endothelial cells, which leads to induction of procoagulant activity (9) and increased adherence of granulocytes (10) and mononuclear cells (1 1). TNFa also regulates interleukin-1 (IL-1) production not only by endothelial cells (12) but also by mononuclear cells of the rheumatoid synovial membrane (13). Because both TNFa and IL-1 can induce synovitis and joint destruction (3), we have postulated that TNFa plays a pivotal role in perpetuating the disease process in rheumatoid arthritis (RA). TNFa has been detected in synovial fluid from patients with various arthritides (14-16), and messen- ger RNA for TNFa has been detected in synovial Arthritis and Rheumatism, Vol. 34, No. 9 (September 1991)