RESUMEN
BACKGROUND: Tobacco smokers have lower serum levels of immunoglobulin (Ig)G, mainly due to lower levels of IgG2, than non-smokers. The component(s) in tobacco smoke responsible for this effect is unknown, but animal studies have implicated nicotine as a major contributor to the immunologic effects of smoking. Does nicotine exposure due to use of smokeless tobacco (oral moist snuff) or nicotine replacement therapy influence serum Ig levels in humans? METHODS: Serum content of Ig classes and IgG subclasses was analysed in 77 non-smoking nicotine consumers, including 48 users of oral moist snuff (smokeless tobacco users) and 29 ex-smokers on nicotine replacement therapy, and compared with 44 healthy controls. Former smokers in any group had quit smoking at least 6 months prior to study entry. Ig class and IgG subclass levels were determined by radial immunodiffusion. Systemic nicotine exposure was excluded and confirmed by measuring urine content of cotinine using a quantitative radioimmunoassay. RESULTS: Ig class and IgG subclass levels did not differ significantly between the groups, with the sole exception of IgG4, which was significantly lower in nicotine consumers than in healthy subjects (0.4 +/- 0.3 vs. 0.6 +/- 0.4 g/l, mean +/- SD, 95% confidence interval [-0.3;-0.05]). There was no correlation between any Ig variable and cotinine concentration. CONCLUSIONS: The decreased levels of IgG and IgG2 seen in tobacco smokers do not seem to be an effect of systemic exposure to nicotine.