Normal circulating serum amyloid P component concentration in systemic sclerosis.
OBJECTIVE
The observation of reduced circulating concentrations of the constitutive plasma pentraxin protein, serum amyloid P component (SAP), in serum samples obtained from a small number of patients with systemic sclerosis (SSc) has been reported as confirmation of an antifibrotic role of this protein. Because neither sustained SAP depletion in humans nor SAP deficiency in mice is associated with fibrosis, we sought to establish rigorously the serum SAP concentration in well-characterized patients with SSc.


METHODS
Serum concentrations of SAP were measured by electroimmunoassay in a cross-sectional cohort of 20 patients with diffuse cutaneous SSc and 12 patients with limited cutaneous SSc, and in a separate 12-month longitudinal cohort of 13 patients with diffuse disease and 37 patients with limited disease. The extent and severity of disease were characterized in detail at the time of serum sampling. Serum concentrations of the classic acute-phase reactants, C-reactive protein and serum amyloid A protein, were measured by immunonephelometric assays.


RESULTS
SAP values were entirely within the normal range, regardless of the extent and severity of disease, apart from a very few isolated raised values associated with acute intercurrent complications causing major acute-phase responses.


CONCLUSIONS
We observed no reduced circulating concentrations of SAP in patients with SSc, nor any evidence of an association between SAP levels and the extent or severity of fibrosis.
Tennent
Glenys A
GA
Centre for Amyloidosis and Acute Phase Proteins, Department of Medicine, University College London, London, UK. g.tennents@medsch.ucl.ac.uk
Dziadzio
Magdalena
M
Triantafillidou
Eva
E
Davies
Phillip
P
Gallimore
J Ruth
JR
Denton
Christopher P
CP
Pepys
Mark B
MB
D000209:Acute-Phase Proteins / Q000378:metabolism; D000328:Adult; D000368:Aged; D002097:C-Reactive Protein / Q000378:metabolism; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D005355:Fibrosis / Q000097:blood / Q000503:physiopathology; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012595:Scleroderma, Systemic / Q000097:blood* / Q000503:physiopathology; D000683:Serum Amyloid P-Component / Q000378:metabolism*; D012720:Severity of Illness Index
D000209:Acute-Phase Proteins; D000683:Serum Amyloid P-Component; D002097:C-Reactive Protein