CD4 and pulmonary emphysema: Bon and collaborators described a statistically significant association between the degree of emphysema by chest CT and serum level of IL-6 and TNF alpha in 234 COPD subjects.[32] TNF alpha is also known to induce synthesis of IL-16[33] a marker mostly associated with asthma but generated by bronchial epithelium and dendritic cells, CD8+ and CD4+ T cells, key elements in COPD pathobiology[28].