title: Could the complement component C4 or its fragment C4d be a marker of the more severe conditions in patients with primary Sjögren's syndrome?
abstract: Our aim is to evaluate the complement component C4 (C4) and its fragment C4d (C4d) levels, focusing on their associations with other markers of B cells' activity in patients with primary Sjögren's syndrome (pSS). Humoral factors C4, C4d, B cell-activating factor (BAFF), κ and λ free light chains (FLCs) and IgG (by immunoassay) were investigated in 58 patients with pSS and in 28 healthy controls. We observed significantly higher levels of BAFF, κ and λ FLC and IgG, and significantly lower level of C4 in pSS patients, while the level of C4d was similar in the both groups. Significantly higher levels of BAFF, κ and λ FLCs, IgG, and significantly lower C4 level were found in anti-SSA/SSB antibodies (Abs) seropositive pSS patients' group comparing with healthy controls. Level of C4d was significantly lower in anti-SSA/SSB Abs seropositive pSS patients comparing with seronegative pSS patients and healthy controls. C4d correlated with C4, anti-SSB Abs level and κ/λ ratio. Significantly higher κ FLC and IgG levels were found in anti-SSA/SSB Abs seronegative pSS patients comparing with healthy controls. Anti-SSA/SSB seropositivity in pSS patients is associated with the decreased level of C4d. These results show that C4d can be an appropriate marker of antibody response and complement activation in pSS patients with Abs, and possibly may show the more severe condition-exhaustion of C4. Further studies are required to determine whether C4d assessment could be a relevant biomarker for the more severe condition and the worse prognosis of pSS.
authors.affiliation: Department of Immunology, State Research Institute Centre for Innovative Medicine, Vilnius, Lithuania.
authors.forename: Gintaras
authors.initials: G
authors.lastname: Sudzius
authors.forename: Diana
authors.initials: D
authors.lastname: Mieliauskaite
authors.forename: Almantas
authors.initials: A
authors.lastname: Siaurys
authors.forename: Rita
authors.initials: R
authors.lastname: Viliene
authors.forename: Irena
authors.initials: I
authors.lastname: Butrimiene
authors.forename: Dainius
authors.initials: D
authors.lastname: Characiejus
authors.forename: Irena
authors.initials: I
authors.lastname: Dumalakiene
mesh_terms: D000328:Adult; D000368:Aged; D000974:Antibodies, Antinuclear / Q000097:blood; D053264:B-Cell Activating Factor / Q000097:blood; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D003181:Complement C4 / Q000032:analysis*; D015935:Complement C4b; D005260:Female; D006801:Humans; D007145:Immunoglobulin kappa-Chains / Q000097:blood; D007146:Immunoglobulin lambda-Chains / Q000097:blood; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000097:blood*; D011237:Predictive Value of Tests; D011379:Prognosis; D012720:Severity of Illness Index; D012859:Sjogren's Syndrome / Q000097:blood / Q000175:diagnosis* / Q000276:immunology
chemical_list: D000974:Antibodies, Antinuclear; D053264:B-Cell Activating Factor; D015415:Biomarkers; D003181:Complement C4; D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains; D010446:Peptide Fragments; C035356:SS-A antibodies; C035357:SS-B antibodies; C505719:TNFSF13B protein, human; D015935:Complement C4b; C032261:complement C4d