A positive feedback mechanism that increases the influx of CD8+ cells into the lungs in COPD has also been described; CD8+ cells in the lungs release IFN-γ, promoting the production of the chemokine CXCL10, which enhances the infiltration of CXCR3 receptor-bearing cells (of the Th1 phenotype), thereby amplifying inflammatory and destructive activity while attracting additional pro-inflammatory cells [67]. Here, IFNG is linked to chronic obstructive pulmonary disease.