1. Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA
2. Division of Rheumatology, Department of Medicine, West Penn Allegheny Health System, Pittsburgh, PA 15212, USA
3. Divisions of Clinical Immunology/Allergy, and Clinical Epidemiology, Department of Medicine, McGill University, Montreal, QC, Canada H3A 1A1
4. Division of Rheumatology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA