TNF and chronic obstructive pulmonary disease: In line with these findings, we observed significantly higher numbers of inflammatory cells, as well as TNF-α-, IL-1β-, IL-13-, IL-17-, IL-22-, and IL-23-producing immune cells (Figure 1), and elevated levels of TNF-α, IL-1β, IL-13, IL-17, IL-22, and IL-23 in the serum samples of COPD patients compared to healthy individuals (Figure 2).