Cigarette smoking enhances T cell activation and a Th2 immune response; an aspect of the pathophysiology in periodontal disease

Smoking is a strong risk factor for periodontitis. Treated patients who smoke show increased risk for further periodontal breakdown, despite receiving maintenance care. Previous work indicated that such patients have a monocytic cytokine response favoring Th2 activity. The purpose of this study was to investigate the T lymphocytic cytokine production representing Th1 and Th2 subpopulations in smokers and non-smokers. Venous blood was collected from 30 treated periodontitis patients (12 smokers) and 24 healthy subjects (12 smokers). Whole blood cell cultures were stimulated and interferon (IFN)-γ and interleukin (IL)-13 were measured in the culture supernatants, representing types 1 and 2 Th subpopulations, respectively. Unadjusted data showed that smokers had more lymphocytes, and higher levels of IFN-γ and IL-13, irrespective of being periodontal patient. However in a multivariate analysis, increased IFN-γ production was not significantly explained by smoking, while higher IL-13 was strongly explained by smoking (21%, p < 0.001). We suggest that the increased Th activity and specifically an elevated Th2 profile in smokers may constitute a risk for smoking patients which may induce conversion of periodontal stability into progressive disease. This phenomenon may be equally important in other conditions, where connective tissue and bone loss are hallmarks of disease pathophysiology.