IL-6/IFN-beta 2 in synovial effusions of patients with rheumatoid arthritis and other arthritides. Identification of several isoforms and studies of cellular sources.
We have looked for IL-6, a cytokine that has immunomodulating and inflammation-associated activities, in joint exudates (fluid and mononuclear cells) from patients with rheumatoid arthritis and other arthritides using both biologic and biochemical assays. IL-6 was assessed by its ability to stimulate alpha 1-antichymotrypsin secretion from the human hepatoma cell line Hep3B clone 2, an activity which is blocked by an antiserum to Escherichia coli derived IL-6, and by the growth of the IL-6-dependent murine hybridoma 7TD1 cell line. IL-6 isoforms in synovial fluid were characterized by immunoaffinity chromatography followed by Western blotting. The presence of IL-1 in synovial fluids and its production by synovial fluid mononuclear cells was monitored by Western blotting and indirect immunofluorescence with polyclonal anti-IL-1 beta antisera. In an analysis of 30 effusions from 27 rheumatoid patients with acutely inflamed joints, abundant quantities of IL-6 (greater than 2 ng/ml) were detected in 23 by the alpha 1-antichymotrypsin bioassay. Several rheumatoid synovial fluids also had elevated IL-6 levels in the 7TD1 bioassay. Seven of nine nonrheumatoid effusions also contained high levels of IL-6 (greater than 2 ng/ml). No IL-1 (less than 0.25 ng/ml) could be detected by Western blotting in 10 rheumatoid effusions even though eight of these contained high levels of IL-6. The IL-6 activity could be neutralized with a rabbit antiserum to rIL-6. Multiple IL-6 isoforms (25, 30, 45 kDa) were present in two rheumatoid and one traumatic effusion studied. Fresh mononuclear cells isolated from various synovial effusions did not appear to make IL-6 constitutively, as no IL-6 could be detected in the media of cells cultured for 12 to 18 h after isolation. Similarly, there was no constitutive production of IL-1 by these cells. However, synovial fluid mononuclear cells could be induced to secrete both IL-6 and IL-1 after stimulation with LPS. The LPS-responsive cells were monocytes and not lymphocytes or dendritic cells. These findings suggest that IL-6 is involved in inflammatory joint disease. However, the primary cells synthesizing it may be located in the synovial lining instead of the joint exudate.
Bhardwaj
N
N
Laboratory of Cellular Physiology, Rockefeller University, New York 10021.
Santhanam
U
U
Lau
L L
LL
Tatter
S B
SB
Ghrayeb
J
J
Rivelis
M
M
Steinman
R M
RM
Sehgal
P B
PB
May
L T
LT
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000032:analysis; D005260:Female; D006801:Humans; D007375:Interleukin-1 / Q000096:biosynthesis; D015850:Interleukin-6; D007378:Interleukins / Q000096:biosynthesis / Q000302:isolation & purification*; D007592:Joint Diseases / Q000378:metabolism / Q000473:pathology; D007963:Leukocytes, Mononuclear / Q000032:analysis; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D013582:Synovial Fluid / Q000032:analysis* / Q000473:pathology
D007375:Interleukin-1; D015850:Interleukin-6; D007378:Interleukins; D008070:Lipopolysaccharides