IL6 and chronic obstructive pulmonary disease: The ratio of IL-6 producing cells to IL-10 producing cells within total B lymphocytes and within all the B cell subsets (Additional file 5: Figure S4a-e) was increased in smokers and COPD patients, compared to healthy controls and reached statistical significance in smokers within the total B lymphocyte, natural effector-, and class-switched memory B cell populations.