Comparative qualitative and quantitative analysis of scleroderma (systemic sclerosis) serologic immunoassays

The heterogeneity of autoantibody specificities occurring in sera from patients with systemic sclerosis (SSc) raised the necessity of developing various methodologies for their detection. A cohort of 150 SSc patients were selected and tested by Indirect Immunofluorescence (IIF), Counterimmunoelectrophoresis (CIE), Immunoblot (IB) using various extracts as antigenic source and RNA precipitation. By preparing a nuclear (IB-nuclear) and a metaphase chromosomal-enriched extract (IB-MC-pellet) from HeLa cells as well as a nucleolar (IB-nucleolar) and a histone (IB-histone) extract from rat liver nuclei, we assessed their sensitivity and specificity for anti-Topo I, anti-U3RNP, anti-H1, anti-snRNPs antibodies and ACA. IB-nuclear revealed the highest frequency of anti-Topo I antibodies, while CIE, IB-nucleolar and IB-MC-pellet, when compared to IB-nuclear showed a sensitivity of 89%, 87% and 95%, respectively. IB-MC-pellet was unique for ACA recognition, while IB-nucleolar and IB-MC-pellet showed excellent sensitivity for anti-U3RNP and anti-H1 antibody detection. We conclude that IB-nuclear is a highly sensitive system for anti-Topo I antibodies determination, but CIE reveals a good sensitivity to be used as a first screening test. IB-nucleolar or IB-MC-pellet are important techniques to detect the variety of antibodies to nucleolus and chromatin-related constituents. A novel specificity against a 28 kD nucleolar protein, non-associated with RNAs is also presented.