Previous studies suggest that smoking affects both the cellular and humoral components of the immune system, leading to leukocytosis, impaired leukocyte function, and increased levels of certain cytokines as well as soluble receptors such as IL 15, IL-1Ra, IL-6, sIL-6R, and vascular endothelial growth factor receptor-3. This evidence concerns the gene IL6 and Increased total leukocyte count.