CD4 and chronic obstructive pulmonary disease: The AUC value for the level of TLR2 expression on circulating CD4+ cells (percentage of CD4+CD282+ cells in the peripheral blood) as a diagnostic marker for COPD was 0.952 (95% CI: 0.887–1.017 and p < 0.05) with a cut-off of 1.4% (discriminating between COPD patients and healthy subjects) of the cells having a sensitivity of 86.7% and a specificity of 100%.