The autoimmune reaction is recently suspected to play a role in the pathogenesis of chronic obstructive lung disease (COPD). As COPD is a systemic disease, the elements of an autoimmune response in circulatory system is of interest. It has been shown that regulatory T cells are important in the control of autoimmunity. There are some data on a role of adiponectin in the regulation of immune reactions. The objective of this study was to assess the elements of autoimmune reaction in the peripheral blood (PB) of patients with COPD. Twenty-eight patients with mild/moderate COPD and 20 healthy volunteers were investigated. Flow cytometry method with mixtures of monoclonal antibodies anti: CD14/CD45, CD3/CD19, CD4/CD25/CTLA4 and CD8/CD25 were used. Concentration of adiponectin was measured using ELISA method. We observed significantly lower proportion of CD4+/CD25+ as well as CD4+/CD25+ (high) cells in COPD patients than in healthy controls (15.3 versus 17.8% and 0.79 versus 1.54%, respectively, P < 0.05). The proportion of CTLA4+ cells in CD25+ cells and the mean fluorescence of CTLA4 on CD4+ cells were higher in patients than in healthy controls (10.4 versus 4.7%, P < 0.05, 189% versus 149%, non significant, respectively). We found significantly elevated concentration of adiponectin in patients when compared to healthy subjects (15.4 versus 8.5 mul/ml, P < 0.05). We found that the adiponectin/BMI ratio correlated with the decrease of FEV(1) %. The results of this study support the possible role of CD4/CD25/CTLA4 cells and adiponectin in the systemic inflammation in COPD.