Relationship between serum levels of IL-18 and IgG1 in patients with primary Sjögren's syndrome, rheumatoid arthritis and healthy controls.
Primary Sjögren's syndrome (SS) is characterized by inflammation in salivary and lachrymal glands, with a local predominance of Th1-like cytokines, as well as the pleiotropic cytokine interleukin (IL) 18. High serum levels of polyclonal IgG are common, with a subclass imbalance in which IgG1 is increased and IgG2 is normal or low. IL-18 is also of pathogenetic importance in rheumatoid arthritis. In the present study we looked for any relationship between serum IL-18 as well as transforming growth factor (TGF) beta1 versus IgA, IgM, and IgG subclass levels in SS (n = 16), rheumatoid arthritis (RA) (n = 15), and healthy controls (n = 15). SS was defined by the revised American-European classification criteria. IL-18 and TGF-beta1 were analyzed with enzyme immunoassays (EIA), and IgG1, IgG2 and IgG3 by single radial immunodiffusion. In the composite group of RA, SS and normal controls, IgG1 and IL-18 were related (R = 0.52, P = 0.0005). No relation was found neither between IL-18 versus IgG2, IgG3 or IgA, nor between serum TGF-beta1 versus any of the immunoglobulins. Since serum levels of IL-18 are related to serum IgG1, IL-18 may be of importance for IgG1 switch and/or release.
Division of Rheumatology, Linköping University Hospital, Linköping, Sweden. per.eriksson@lio.se
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Eriksson
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Andersson
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Ekerfelt
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Ernerudh
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Skogh
D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood*; D020382:Interleukin-18 / Q000097:blood*; D008875:Middle Aged; D012859:Sjogren's Syndrome / Q000276:immunology*; D018709:Statistics, Nonparametric; D016212:Transforming Growth Factor beta / Q000032:analysis
D007070:Immunoglobulin A; D007074:Immunoglobulin G; D020382:Interleukin-18; D016212:Transforming Growth Factor beta