Some studies of SLE patients demonstrated an increased expression of anti-dsDNA antibodies amongst smokers [58] while other investigators did not find a clear association between smoking status and individual autoantibodies.[37] In the case of RA patients, smoking has been associated with increased ANA positivity in men and RF in women.[59, 60] These seemingly opposite results suggest that the role of smoking on pathogenic autoantibodies differs from one autoimmune disease to another and may be a good example of gene-environment interaction. This evidence concerns the gene BTG3 and systemic lupus erythematosus.