1. ¹Department of Medicine, University of Minnesota Medical School, Minneapolis, MN, USA
2. ²Department of Arthritis and Immunology, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
3. ³Department of Epidemiology and Biostatistics, Case Western Reserve University, Cleveland, OH, USA
4. ⁴Department of Public Health Sciences, Wake Forest University School of Medicine, Winston-Salem, NC, USA

Correspondence: Dr KL Moser, University of Minnesota, 5–140 MCB, 420 Washington Ave. SE, Minneapolis, MN 55455, USA. E-mail: moserk@umn.edu

Received 24 February 2006; Revised 8 May 2006; Accepted 8 May 2006; Published online 15 June 2006.

Abstract

Autoantibodies are clinically relevant biomarkers for numerous autoimmune disorders. The genetic basis of autoantibody production in systemic lupus erythematosus (SLE) and other autoimmune diseases is poorly understood. In this study, we characterized autoantibody profiles in 1506 individuals from 229 multiplex SLE pedigrees. There was strong familial aggregation of antinuclear antibodies (ANAs), anti-double-stranded DNA (dsDNA), anti-La/SSB, anti-Ro/SSA, anti-Sm, anti-nRNP (nuclear ribonucleoprotein), IgM antiphospholipid (aPL) antibodies (Abs) and rheumatoid factor (RF) across these families enriched for lupus. We performed genome-wide linkage analyses in an effort to map genes that contribute to the production of the following autoantibodies: Ro/SSA, La/SSB, nRNP, Sm, dsDNA, RF, nuclear and phospholipids. Using an approach to minimize false positives and adjust for multiple comparisons, evidence for linkage was found to anti-La/SSB Abs on chromosome 3q21 (adjusted P=1.9 10^-6), to anti-nRNP and/or anti-Sm Abs on chromosome 3q27 (adjusted P=3.5 10^-6), to anti-Ro/SSA and/or anti-La/SSB Abs on chromosome 4q34–q35 (adjusted P=3.4 10^-4) and to anti-IgM aPL Abs on chromosome 13q14 (adjusted P=2.3 10^-4). These results support the hypothesis that autoantibody production is a genetically complex trait. Identification of the causative alleles will advance our understanding of critical molecular mechanisms that underlie SLE and perhaps other autoimmune diseases.