The aims of this study were to evaluate the content of sCD25, sCD38, and sCD8 molecules and complexes of sHLA-I-CD8 in the blood serum and exhaled breath condensate and to determine the relationship concentration of these soluble molecules and the ventilation lung function in patients with moderate-to-severe COPD in different disease periods. Here, CD8A is linked to chronic obstructive pulmonary disease.