Anti-C1q antibodies and antiendothelial cell antibodies in systemic lupus erythematosus - relationship with disease activity and renal involvement.
The aim of this study was to investigate the relationship between the presence and titre of antibodies against C1q (anti-C1q Ab) and disease activity and renal involvement in patients with systemic lupus erythematosus (SLE). Anti-C1q Ab were measured in 79 patients with SLE (70 women and 9 men; mean age 41.7 years; mean disease duration 8.4 years): 19 patients had active disease with lupus nephritis, 8 active disease without nephritis, 26 inactive disease with nephritis and 26 inactive disease without nephritis. Anti-dsDNA antibodies (EIA and immunofluorescence), antiendothelial cell antibodies (AECA) and complement levels (C3, C4, total haemolytic complement activity) were determined in parallel. Anti-C1q Ab were positive in 49%, anti-dsDNA Ab in 61% and AECA in 19% of the patients, respectively. Significantly higher titres of anti-C1q Ab were found in patients with active disease compared with those with inactive SLE ( P < 0.01). Serum levels of anti-C1q Ab showed a positive correlation with anti-dsDNA Ab and SLEDAI score ( P < 0.01) and a negative correlation with C3 ( P < 0.05), C4 ( P < 0.01) and CH50U ( P < 0.01). The presence of anti-C1q Ab was not different between patients with or without nephritis. In patients with ( P < 0.05) and without nephritis ( P < 0.01) the frequency of anti-C1q Ab was significantly higher in active patients compared with inactive patients. Both anti-C1q and anti-ds-DNA Ab were detectable in 74% of patients with active nephritis but only in 30% of all other patients ( P=0.001). None of the patients with active nephritis was negative for anti-C1q and anti-dsDNA Ab, whereas 37% of the patients without active nephritis were negative for both antibodies ( P < 0.01). Sensitivity, specificity, positive and negative predictive values for active lupus nephritis among SLE patients were 100%, 50%, 51.9% and 100% for anti-dsDNA Ab (EIA) and 74%, 70%, 57% and 89.4% for positive findings of both anti-dsDNA and anti-C1q Ab. The presence and titre of anti-C1q-Ab in SLE are related to disease activity. Absence of anti-dsDNA Ab excludes active nephritis; positive findings of both anti-dsDNA Ab and anti-C1q Ab are of relatively high specificity for active nephritis.
Friedrich-Schiller-University of Jena, Jena, Germany. peter.oelzner@med.uni-jena.de
P
P
Oelzner
B
B
Deliyska
R
R
Fünfstück
G
G
Hein
D
D
Herrmann
G
G
Stein
D000293:Adolescent; D000328:Adult; D000368:Aged; D000888:Antibodies, Anti-Idiotypic / Q000032:analysis / Q000276:immunology*; D001323:Autoantibodies / Q000032:analysis / Q000276:immunology*; D015415:Biomarkers / Q000097:blood; D015331:Cohort Studies; D015922:Complement C1q / Q000032:analysis / Q000276:immunology*; D003176:Complement C3 / Q000032:analysis / Q000276:immunology; D003181:Complement C4 / Q000032:analysis / Q000276:immunology; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000175:diagnosis / Q000276:immunology*; D008181:Lupus Nephritis / Q000175:diagnosis / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D011336:Probability; D011379:Prognosis; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric
D000888:Antibodies, Anti-Idiotypic; D001323:Autoantibodies; D015415:Biomarkers; D003176:Complement C3; D003181:Complement C4; C087589:anti-endothelial cell antibody; D015922:Complement C1q