CD4 and chronic obstructive pulmonary disease: Xiong et al. showed that CD4+CD25+, CD4+ Treg, CD8+CD25+ and CD8+ Tregs were expressed in the peripheral blood of patients with acute exacerbations of COPD with a significant correlation with age, disease’s course, smoking index, quantity of white cells, and blood pH, while no correlations were found between these cells and IL-10 [10].