CD8A and chronic obstructive pulmonary disease: Sirtuin 1 (class III NAD-dependent histone deacetylase involved in silencing transcription of genes that produce inflammatory cytokines) expression is also reported to be diminished in the CD8+CD28null T cells of COPD patients and has been postulated to be associated with steroid resistance, increased secretion of proinflammatory cytokines and disease severity.