TNF and chronic obstructive pulmonary disease: Importantly, immune cells that play a crucially important pathogenic role in the development of cigarette smoke-induced COPD (TNF-α-producing, classically activated (M1) macrophages and neutrophils, as well as IL-17-producing lymphocytes) were found in significantly higher numbers in the injured lungs of BALB/c mice compared to C57BL/6 mice, indicating the advantage of using BALB/c mice in COPD-related animal studies [10–12].