Serum amyloid A and C-reactive protein concentrations are differently associated with markers of autoimmunity in patients with primary Sjögren's syndrome.
OBJECTIVE
Primary Sjögren's syndrome (pSS) is an autoimmune disease in which the concentration of the acute-phase protein serum C-reactive protein (CRP) is low. We investigated whether levels of another acute-phase protein, serum amyloid A (SAA), are increased in patients with pSS and whether the immunological markers in patients with pSS are associated with variation in SAA levels.


METHODS
Serum SAA concentrations were measured by ELISA in 74 patients with pSS and in 56 control subjects with sicca symptoms.


RESULTS
Median SAA levels did not differ significantly between patients with pSS and subjects with sicca symptoms. In patients with pSS SAA concentrations correlated significantly with age, leukocyte count, CRP, interleukin 6, and C4. Unlike CRP, there was a significant inverse correlation between SAA and serum IgG levels and anti-SSA antibody titers, as well as a trend towards an inverse correlation between SAA and antinuclear antibody and rheumatoid factor titers.


CONCLUSIONS
Our data imply that high SAA production could constitute a protective element in pSS: high SAA levels inhibit in particular various signs of B cell hyperreactivity, i.e., IgG and autoantibody production.
Pertovaara
Marja
M
Department of Internal Medicine, Section of Rheumatology, Tampere University Hospital, Tampere, Finland. marja.pertovaara@uta.fi
Jylhävä
Juulia
J
Uusitalo
Hannu
H
Pukander
Juhani
J
Helin
Heikki
H
Hurme
Mikko
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D015415:Biomarkers / Q000097:blood*; D002097:C-Reactive Protein / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012469:Salivary Glands / Q000473:pathology; D000685:Serum Amyloid A Protein / Q000378:metabolism*; D012859:Sjogren's Syndrome / Q000097:blood* / Q000276:immunology* / Q000473:pathology
D015415:Biomarkers; D000685:Serum Amyloid A Protein; D002097:C-Reactive Protein