COPB2 and chronic obstructive pulmonary disease: The impairment of the retrograde Golgi-to-ER transport caused by mutations in different COPI subunit proteins was previously described to result in an increased ER stress in activated T and/or B cells, heterozygous for mutations in the WD40 domain of COPA or homozygous for mutations in COPG1, or in unstimulated patient-derived fibroblasts, heterozygous for mutations in COPD or homozygous for mutations in COPB2 (47, 61–63).