Neutralizing antibodies (NAbs) to interferon β (IFNβ) products that develop during treatment are associated with a loss of clinical efficacy.

The aim of this study was to investigate the influence of smoking habits on the risk of developing NAbs to IFNβ, in the treatment of multiple sclerosis (MS).

This report is based on 695 MS patients treated with IFNβ-1a, included in two Swedish case-control studies that collected information on smoking habits. Using logistic regression, the development of NAbs to IFNβ-1a among current smokers was compared with that of non-smokers, by calculating the odds ratio (OR) with a 95% confidence interval (CI).

Current smokers showed an increased risk of developing NAbs to IFNβ-1a, compared with non-smokers (OR 1.9; 95% CI 1.3–2.8; p = 0.002). There were no gender differences. We observed no association between past smoking and the risk of developing NAbs to IFNβ-1a.

The finding that current smokers have an increased risk of developing NAbs to IFNβ-1a has implications, both for the practical care and the treatment of MS; it also provides an interesting perspective of the lungs as an immune-reactive organ, reacting upon irritation.