IL13 and chronic obstructive pulmonary disease: The use of antibiotics, such as azithromycin, usually used in COPD therapy to decrease the number of exacerbations, generates a decrease in bacterial diversity and an increase in microbial metabolites (glycolic acid, linoleic acid, and indole-3-acetate), resulting in altered expression of cytokines that regulate the immune response, such as IL-12, IL-13, CXCL-1, and TNF-α [40,45,64].