IL-4 production is increased in cigarette smokers

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Abstract
Cigarette smoking has been associated with both increases in serum levels of total IgE and an increased risk of developing allergic-like symptoms. IL-4 and interferon-gamma (IFN-γ) have reciprocal roles in the regulation of IgE synthesis, and as such prompted us to evaluate, in smokers, the production of these two cytokines. We demonstrate that phytohaemagglutinin (PHA)-induced IL-4 production by peripheral blood mononuclear cells (PBMC) of smokers (n= 19) is significantly higher than that of non-smokers (n=10, p < 0·005). In addition, PBMC from heavy smokers, defined by the number of cigarettes smoked per day, produced significantly higher levels of IL-4 than those of light smokers. No difference between the groups was found for IFN-y production. Our data suggest an imbalance in cytokine production occurring in individuals who smoke. This imbalance, favouring IL-4 production, may be part of the mechanism responsible for the observed increases in serum IgE and allergic-like symptoms associated with cigarette smoking.