Secondhand smoke induces allergic sensitization in mice

Epidemiological studies have suggested increased prevalence of atopy in chi ldren of maternal smokers. Although secondhand smoke or environmental tobac co smoke (ETS) has been shown to augment allergic responses, its role in at opic sensitization is still controversial. We studied whether ETS could ini tiate a Th2 response and thus induce primary allergic sensitization. Mice w ere exposed for 10 consecutive days to either 1% aerosolized OVA, ETS (5 ci garettes), or both ETS and OVA. C57BL/6 mice receiving both ETS and OVA dev eloped OVA-specific IgE and IgG1, 12, 14, and 25 days after the initial exp osure, whereas those receiving OVA alone did not. Thirty days after the ini tial challenge (20 days after its completion), mice were re-exposed to OVA. Bronchoalveolar lavage performed 24 h later revealed an influx of eosinoph ils in the group initially challenged with both ETS and OVA, but not in tho se exposed to ETS alone or OVA alone. Increases in IL-5, GM-CSF, and IL-2 w ere observed in bronchoalveolar lavage from this OVA/ETS-exposed group, whe reas IFN-gamma levels were significantly inhibited. These results suggest t hat ETS can induce allergic sensitization to a normally harmless Ag, and th ey may explain why secondhand smoke is a major risk factor for the developm ent of allergy In children.