Abstract
IntroductionThe finding of antinuclear antibody (ANA) positivity in a healthy individual is usually of unknown significance and in most cases is benign. However, a subset of such individuals is at risk for development of autoimmune disease. We examined demographic and immunological features that are associated with ANA positivity in clinically healthy persons to develop insights into when this marker carries risk of progression to lupus.MethodsBiological samples from healthy individuals and patients with systemic lupus erythematosus (SLE) were obtained from the Dallas Regional Autoimmune Disease Registry (DRADR). Measurements carried out on serum samples included ANA, extractable nuclear antibodies (ENA) and autoantibody profiling using an array with more than 100 specificities. Whole blood RNA samples from a subset of individuals were used to analyze gene expression on the Illumina platform. Data were analyzed for associations of high ANA levels with demographic features, the presence of other autoantibodies and with gene expression profiles.ResultsOverall, ANA levels are significantly higher in females than in males and this association holds in patients with the autoimmune diseases lupus and rheumatoid arthritis (RA) as well as in healthy controls (HC). Age was not significantly associated with ANA levels and the elevated ANA values could not be explained by higher IgG levels. Another autoantibody, anti- cyclic citrullinated peptide (CCP), did not show gender dimorphism in rheumatoid arthritis (RA) or healthy individuals. The autoantigen array showed significant elevations of other autoantibodies in high ANA HCs. Some of these autoantibodies were directed to antigens in skin and others were related to autoimmune conditions of kidney, thyroid or joints. Gene expression analyses showed a greater prevalence of significantly upregulated genes in HCs with negative ANA values than in those with significant ANA positivity. Genes upregulated in high ANA HCs included a celiac disease autoantigen and some components of the Type I interferon (IFN) gene signature.ConclusionsRisks for ANA positivity include female gender and organ-specific autoimmunity. Upregulation of skin-specific autoantibodies may indicate that early events in the break of tolerance take place in cutaneous structures. Some of these changes may be mediated by Type I IFN. Blood profiling for expressed autoantibodies and genes has the potential to identify individuals at risk for development of autoimmune diseases including lupus.
Highlights
The finding of antinuclear antibody (ANA) positivity in a healthy individual is usually of unknown significance and in most cases is benign
Since ANA positivity is for all practical purposes a requirement for systemic lupus erythematosus (SLE) diagnosis, it must be assumed that individuals who are in preclinical disease stages are represented in the ANA positive healthy population
For the subset of 401 healthy controls (HC), the average ANA was 19.5 ELISA units (EU) and 101 individuals were in the positive range
Summary
The finding of antinuclear antibody (ANA) positivity in a healthy individual is usually of unknown significance and in most cases is benign. Since ANA positivity is for all practical purposes a requirement for SLE diagnosis, it must be assumed that individuals who are in preclinical disease stages are represented in the ANA positive healthy population. We have considered the possibility that other blood markers could be used to differentiate benign ANA positivity from that which carries a high risk of autoimmune disease. These markers may include other autoantibodies, since it is well-known that autoantibody positivity increases in quantity and complexity in years preceding a diagnosis of SLE [4]. Gene dysregulation in peripheral blood cells has been closely associated with SLE diagnosis and disease status, so changes in gene expression may signal a condition with enhanced risk
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