5Gratacos J, Collado A, Filella X. Serum cytokines [ IL - 6,TNF- alpha, IL - 1 beta and IFN - gamma ] in ankylosing spondylitis: a close correlation between serum IL - 6 and disease activity and severity. Br J Rheumatol, 1994; 33 ( 10 ):927
6Saxne T, Palladino MA Jr, Heinegard D, et al. Detection of tumor necrosis factor - but not tumor necrosis factor- in rheumatoid arthritis synovial fluid and serum. Arthritis Rheum, 1998;31:1041
7Firestein GS. Invasive fibroblast - like synoviocytes in rheumatoid arthritis passive responders or transformed aggressor? Arthritis Rheum, 1996; 39: 1781
