TNFRSF1A and chronic obstructive pulmonary disease: Therefore, in the present study we investigated expressions of proinflammatory IL-6, TNF-α, TNFRSF1A, CD68 (macrophage cell surface receptor), and of proapoptotic caspase-3 (CASP3) and Bax, and their relationships to the metabolic phenotype in patients with COPD.