TABLE 1

Main results of studies focusing on interleukin (IL)-17 and IL-22 concentrations and T-helper type 17 cell and IL-17-producing CD8⁺ T-cell proportions in the blood of chronic obstructive pulmonary disease (COPD) patients

First author, year [reference]	Method	Measure	Results
Andelid, 2015 [20]	ELISA	IL-17A levels	HNS (n=10) > HS (n=10) > OPD-CB (n=60)^#
Jin, 2014 [21]	ELISA	IL-17A levels	AE-COPD (n=21) > HNS (n=20) > S-COPD (n=23)
Sun, 2016 [22]	ELISA	IL-17A levels	AE-COPD (n=24) > S-COPD (n=26) = HS (n=23)
Wang, 2015 [23]	ELISA	IL-17A levels	S-COPD (n=65) > HS (n=35) = HNS (n=31)^¶
Zhang, 2013 [24]	ELISA	IL-17A levels	S-COPD (n=94) > HS (n=23) = HNS (n=22)^§
Zhang, 2011 [83]	ELISA	IL-17A levels	HC (n=31) > AE-COPD (n=73)
Zou, 2017 [25]	ELISA	IL-17A levels	AE-COPD (n=60) > S-COPD (n=60) > HC (n=40)
Wang, 2015 [23]	ELISA	IL-22 levels	S-COPD (n=65) > HS (n=35) > HNS (n=31)^¶
Zhang, 2013 [24]	ELISA	IL-22 levels	S-COPD (n=94) = HS (n=23) > HNS (n=22)
Imani, 2016 [26]	Flow cytometry	IL-17A⁺ CD4⁺ T-cells	S-COPD (n=9) > HNS (n=8)
Li, 2015 [27]	Flow cytometry	IL-17A⁺ CD4⁺ T-cells	S-COPD (n=21) = HS (n=21) > HNS (n=21)
Li, 2014 [28]	Flow cytometry	IL-17A⁺ CD4⁺ T-cells	AE-COPD (n=32) > S-COPD (n=36) = HS (n=40)
Paats, 2012 [29]	Flow cytometry	IL-17A⁺ and IL-22⁺ CD4⁺ T-cells	S-COPD (n=30) = HNS (n=10)
Qiu, 2016 [30]	Flow cytometry	IL-17A⁺ CD4⁺ T-cells	S-COPD (n=38) > HS (n=20) = HNS (n=20)
Solleiro, 2015 [31]	Flow cytometry	IL-17A⁺ CD4⁺ T-cells	TS-COPD (n=24) > BE-COPD (n=17) > HNS (n=20)
Sun, 2016 [22]	Flow cytometry	IL-17A⁺ CD4⁺ T-cells	AE-COPD (n=24) > S-COPD (n=26) = HS (n=23)
Vargas-Rojas, 2011 [32]	Flow cytometry	IL-17A⁺ CD4⁺ T-cells	S-COPD (n=39) > HS (n=14) = HNS (n=15)
Wang, 2015 [23]	Flow cytometry	IL-17A⁺ CD4⁺ T-cells	S-COPD (n=65) > HS (n=35) > HNS (n=31)^¶
Zhang, 2016 [34]	Flow cytometry	IL-17A⁺ CD4⁺ T-cells	S-COPD (n=29) > HS (n=24) = HNS (n=27)
Paats, 2012 [29]	Flow cytometry	IL-17F⁺ CD4⁺ T-cells	S-COPD (n=30) > HNS (n=10)
Paats, 2012 [29]	Flow cytometry	IL-17A⁺, IL-17F⁺ and IL-22⁺ CD8⁺ T-cells	S-COPD (n=30) = HNS (n=10)
Xu, 2016 [33]	Flow cytometry	IL-17A⁺ CD8⁺ T-cells	S-COPD (n=25) > HS (n=23) = HNS (n=15)

Data are presented as comparisons of cytokines levels or cells proportions in the blood of healthy nonsmokers (HNS), healthy smokers (HS) and patients with COPD. OPD-CB: obstructive pulmonary disease including chronic bronchitis; AE-COPD: acute exacerbation of COPD; S-COPD: stable COPD; HC: healthy controls without data on smoking status; TS-COPD: COPD related to tobacco smoking; BE-COPD: COPD related to biomass exposure. ^#: HNS is significantly different from OPD-CB, but HS is not significantly different from the two other groups; ^¶: higher cytokine levels or cell proportions in severe/very severe COPD compared to mild/moderate COPD; ^§: IL-17A levels increase with COPD stages.