title: Lymphocyte-bound complement activation products as biomarkers for diagnosis of systemic lupus erythematosus.
abstract: Systemic lupus erythematosus (SLE) is frequently misdiagnosed due to the lack of definitive diagnostic tests. The purpose of this study was to determine specifically whether complement activation products (CAP) are deposited on lymphocytes of SLE patients and whether lymphocyte-bound CAP (LB-CAP) may serve as novel biomarkers for the diagnosis of SLE. We conducted a cross-sectional study of 224 patients with SLE, 179 patients with other diseases, and 114 healthy controls. LB-CAP on peripheral blood lymphocytes was measured by flow cytometry. Diagnostic utility of LB-CAP was determined by receiver operating characteristic (ROC) analysis. Significantly elevated levels of C4d and C3d were detected specifically on T and B lymphocytes (designated T-C4d, T-C3d, B-C4d, and B-C3d) of SLE patients. As diagnostic tools, T-C4d and B-C4d, respectively, were 56% sensitive/80% specific and 60% sensitive/82% specific in differentiating SLE from other diseases. Moreover, compared with measurement of anti-dsDNA, serum C3, or serum C4, measurement of T-C4d/B-C4d was significantly more sensitive in identifying SLE patients during a single clinic visit. This is the first investigation of lymphocytes bearing complement activation products in human disease. T-C4d and B-C4d have high diagnostic sensitivity and specificity for SLE and may have added value to current laboratory tests for SLE diagnosis.
authors.affiliation: University of Pittsburgh School of Medicine, Pittsburgh, PA, USA. liu5@pitt.edu
authors.forename: Chau-Ching
authors.initials: CC
authors.lastname: Liu
authors.forename: Amy H
authors.initials: AH
authors.lastname: Kao
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Hawkins
authors.forename: Susan
authors.initials: S
authors.lastname: Manzi
authors.forename: Abdus
authors.initials: A
authors.lastname: Sattar
authors.forename: Nicole
authors.initials: N
authors.lastname: Wilson
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Ahearn
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001402:B-Lymphocytes / Q000276:immunology; D015415:Biomarkers / Q000378:metabolism*; D003167:Complement Activation; D015935:Complement C4b / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000175:diagnosis* / Q000276:immunology*; D008214:Lymphocytes / Q000166:cytology*; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000378:metabolism; D012680:Sensitivity and Specificity; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D015415:Biomarkers; D010446:Peptide Fragments; D015935:Complement C4b; C032261:complement C4d