These results support previous findings from Wang and colleagues who demonstrated that the number of Th17 cells was increased in the peripheral blood of moderate-to-severe COPD patients, along with the levels of ROR-γT (an important transcription factor of Th17 cells), and many other inflammatory mediators, including IL-17A, IL-6, IL-21, IL-22, and IL-23. This evidence concerns the gene IL21 and chronic obstructive pulmonary disease.