TNF and chronic obstructive pulmonary disease: Moreover, in healthy subjects and those with stable COPD, the 1 μg/mL concentration of the VGVAPG peptide increased mRNA and protein expression of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNFα), and interleukin-8 (IL-8), while a higher concentration (10 μg/mL) of the VGVAPG peptide did not significantly influence the above-described parameters [14].