Demographic characteristicsA total of 150 participants were recruited: 90 COPD patients and 60 clinically healthy persons for the control group. The COPD patients consisted of 50 smokers (COPD/tobacco) and 40 patients who had previously TB (COPD/post-TB). Spirometric characteristicsIn the COPD/tobacco patients, FEV1 ranged from 20.3% to 64.60% and in the COPD/post-TB patients, itranged from 30% to 79%. In the control group, FEV1/FVC ranged from 70% to 97%. The FEV1/FVC ratio of COPD/tobacco patients ranged from 35% to 68% and in the COPD/post-TB subgroup, it ranged from 35% to 74.35%. the FEV1 and FEV1/FVC ratio was lower in the COPD/tobacco subgroup than in the COPD/post-TB subgroup with p-values of 0.014 and 0.033 respectively. As a result, the stage of COPD was more advanced in COPD/tobacco patients compared to COPD/post-TB patients with a p-value of 0.032 (Table I and Table II)
Concentrations of cytokines in participantsThe detected cytokines in sputum were anti-cytokines (IL-1RA), pro-inflammatory cytokines (IL-1α, IL-1β, IL-6, IL-17 and TNF-α), chemokines (MCP-1, IL-8, MIP-1α, MIP-1β, GRO, IP-10 and sCD40L) and growth factors (VEGF, G-CSF and GM-CSF). Other cytokines such as IFN-α, IFN-γ, IL-10, IL-12, MDC, PDGF, IL-15, IL-2, IL-4, IL-7 and RANTES were not detected in the sputum of either the COPD patients or the control group.Table III shows the mean (± SD) concentrations of cytokines in sputum in the three groups: in patients with COPD, the levels of cytokines such as IL-1RA, IL-1α, IL-1β, MIP-1β, sCD40L and VEGF were statistically higher compared to the control group with p-values all lower at 0.05.IL-6 and TNF-α were higher in smokers. GRO concentration was higher in COPD/post-TB patients. Levels of IL-17 and GM-CSF were higher in COPD patients, but with no statistically significant difference. There was also no statistically significant difference in cytokine concentrations such as G-CSF, MIP-1α and IP-10.
Concentration of IL-1RA
In the control group, the maximum concentration of IL-1RA was 1590 pg/mLwith an average of 637.7±191.3 pg/mL. In the COPD/tobacco subgroup, the concentration of IL-1RA ranged from 147.0 pg/mL to 4686 pg/mL with a mean of 1720 ±491.1pg/mL. In the COPD/post-TB subgroup, the lowest concentration of IL-1RA was 109.3 pg/mL and the highest was 6566 pg/mL with a mean of 1945 ± 873.1).No statistically significant difference in IL-1RA concentration was found between the COPD/tobacco and COPD/post-TB subgroups (p = 0.8). IL-1RA concentration was higher in the COPD/tobacco subgroup compared to the control group (p = 0.014) and higher in the COPD/post-TB subgroup compared to the control group (p = 0.014) (Figure 1).Concentration of IL-1α In the control group, the maximum concentration of IL-1α was 1726 pg/mL with an average of 539.1 ± 198.6 pg/mL. In the COPD/tobacco subgroup, the IL-1α concentration ranged from 81.06 pg/mL to 3937 pg/mL with a mean of 1555 ± 360.7 pg/mL. In the COPD/post-TB subgroup, the lowest concentration of IL-1α was 88.94 pg/mL and the highest was 1914 pg/mL with a mean of 821.2 ± 205.7 pg/mL. No statistically significant difference in IL-1α concentration was found between the COPD/tobacco and COPD/post-TB subgroups (p = 0.8). IL-1α concentration was higher in the COPD/tobacco subgroup compared to the control group (p = 0.006) and higher in the COPD/post-TB compared to the control group (p = 0.029) (Figure 2 Concentration of IL-1βIn the control group, the minimum concentration of IL-1β was 0.01 pg/mL and the maximum was 34.36 pg/mL with a mean of 9.410 ± 3.781 pg/mL. In the COPD/tobacco subgroup, the concentration of IL-1β ranged from 1.1 pg/mL to 1531 pg/mL (mean =296.4 ± 143.5 pg/mL). In the COPD/post-TB subgroup, the lowest IL-1β concentration was 0.58 and the highest was 578.7 pg/mL (mean = 137.9 ± 65.25 pg/mL). No statistically significant difference in IL-1β concentration was found between the COPD/tobacco and COPD/post-TB subgroups (p = 0.390). IL-1β concentration was higher in the COPD/tobacco subgroup compared to the control group (p = 0.025) and higher in the COPD/post-TB subgroup compared to the control group with (p = 0.048) (Figure 3). Concentration of IL-6 In the control group, the minimum concentration of IL-6 was 0.0 pg/mL and the maximum was 54.14 pg/mL (mean = 11.64 ± 2.90 pg/mL). In the COPD/tobacco subgroup, the IL-6 concentration ranged from 0.44 pg/mL to 83.27 pg/mL (mean = 16.23 ± 7.768 pg/mL). In the COPD/post-TB subgroup, the lowest IL-6 concentration was 0.0 pg/mL and the highest was 63.07 pg/mL with a mean of 137.9 ± 65.25 pg/mL. IL-6 concentration was higher in the COPD/tobacco than in in COPD/post-TB subgroup (p = 0.049), and higher in the COPD/tobacco subgroup compared to the control group (p = 0.033). No statistically significant difference in IL-6 concentration was found between the COPD/post-TB subgroup and control group (p = 0.665) (Figure 4).
Concentration of IL-17
In the control group, the minimum concentration of IL-17 was 0.0 pg/mL and the maximum concentration was 4.27 pg/mL (mean = 1.421± 0.23 pg/mL). In the COPD/tobacco subgroup, the maximum concentration of IL-17 was 5.230 pg/mL with a mean of 1.54 ± 0.2650 pg/mL. In the COPD/post-TB subgroup, the lowest concentration of IL-17 was 1.33 pg/mL and the highest concentration was 4.06 pg/mL with a mean of 2.412 ± 0.41pg/mL. The difference in IL-17 concentration between the COPD/tobacco and the COPD/post-TB subgroups was not statistically significant (p = 0.053). IL-17 concentration was higher in the COPD/tobacco subgroup compared to the control group (p = 0.041) and higher in the COPD/post-TB subgroup compared to the control group (p = 0.045) (Figure 5).
Concentration of TNF-α
In the control group, the minimum concentration of TNF-α was 0.0 pg/mL and the maximum concentration was 26.01 pg/mL (mean = 1.880 ± 0.31 pg/mL). In the COPD/tobacco subgroup, the maximum concentration of TNF-α was 43.01 pg/mL (mean = 7.112 ± 4.542 pg/mL). In the COPD/post-TB subgroup, the lowest concentration of TNF-α was 0.0 pg/mL and the highest was 5.14 pg/mL (mean = 1.110± 0.5649 pg/mL). TNF-α concentration was higher in the COPD/tobacco subgroup compared to the COPD/post-TB subgroup (p = 0.021) and higher in the COPD/tobacco subgroup compared to the control group (p = 0.048). Not statistically significant difference was found between the COPD/post-TB subgroup and the control group (p = 0.126) (Figure 6).
Concentration of IL-8
In the control group, the concentration of IL-8 varied from 7.5 pg/mL to 541.4 pg/mL with a mean of 135.5 ± 30.93 pg/mL. In the COPD/tobacco subgroup, the concentration of IL-8 ranged from 4.40 pg/mL to 2250 pg /mL with an average of 493.1± 244.9 pg/mL. In the COPD/post-TB subgroup, the lowest concentration of IL-8 was 1.2 pg/mL and the highest was 630.7 pg/mL with an average of 103.0 ± 68.58 pg/mL. IL-8 concentration was higher in the COPD/tobacco subgroup compared to the COPD/post-TB subgroup (p = 0.016) and higher in the COPD/tobacco subgroup compared to the control group (p = 0.009). No statistically significant difference in IL-8 concentration was found between the COPD/post-TB subgroup and the control group (p = 0.714) (Figure 7).
Concentration of MIP-1β In the control group, the minimum concentration of MIP-1β was 0.0 pg/mL and the maximum concentration was 389.4 pg/mL with a mean of 81.65 ± 20.27 pg/mL. In the COPD/tobacco subgroup, the concentration of MIP-1β ranged from 18.20 pg/mL to 780.9 pg/mL (mean = 181.1 ± 63.57 pg/mL). In the COPD/post-TB subgroup, the lowest concentration of MIP-1β was 9.630 pg/mL and the highest was 872.9 pg/mL (mean =224.1 ± 103.4 pg/mL). No statistically significant difference in MIP-1β concentration was found between the COPD/tobacco and the COPD/post-TB subgroups (p = 0.71), but it was higher in the COPD/tobacco subgroup compared to the control group (p = 0.012) and without statistically significant difference between the COPD/post-TB subgroup and control group (p = 0.16) (Figure 8). Concentration of GRO In the control group, the concentration of GRO varied from 0.0 pg/mL to 13518 pg/mL with a mean of 2563 ± 1617 pg/mL. In the COPD/tobacco subgroup, the concentration of GRO ranged from 0.0 pg:mL to 4850 pg/mL with a mean of 2563 ± 1617 pg/mL. In the COPD/post-TB subgroup, the lowest concentration of GRO was 132.9 pg/mL and the highest was 105133 pg/mL (mean = 1721 ± 977.7 pg /mL). No statistically significant difference in GRO concentration was found between the COPD/tobacco and the COPD/post-TB subgroups (p = 0.37) and between the COPD/tobacco subgroup compared to control group (p = 0.404), but it was higher in the COPD/post-TB sub-group compare to control group (p = 0.028) (Figure 9).
Concentration of sCD40L
In the control group, the minimum concentration of sCD40L was 0.0 pg/mL and the maximum concentration was 2.600 pg/mL with a mean of 0.286 ± 0.164 pg/mL. In the COPD/tobacco subgroup, the concentration of sCD40L ranged from 0,0 pg/mL to 8.570 pg/mL with a mean of 1.506 ± 0.441 pg/mL . In the COPD/post-TB subgroup, the lowest sCD40L concentration was 0.0 pg/mL and the highest was 4.760 pg/mL with a mean of 1.958 ± 0.384 pg/mL. No statistically significant difference in sCD40L concentration was found between the COPD/tobacco and the COPD/post-TB subgroups (p = 0.462). The difference between the COPD/tobacco subgroup and the control group was not statistically significant (p = 0.058), but the sCD40L concentration was higher in the COPD/post-TB subgroup compared to the control group (p = 0.001) (Figure 10).
Concentration of VEGF
In the control group, the concentration of VEGF varied from 0.0 pg/mL to 1280 pg/mL with a mean of 332 ± 155.8 pg/mL. In the COPD/tobacco subgroup, the concentration of VEGF ranged from 33.63 pg/mL to 1214 pg/mL (mean = 435.2 ± 130.2 pg/mL). In the COPD/post-TB subgroup, the lowest concentration of VEGF was 0.0 pg/mL and the highest was 1143 pg /mL (mean = 333.9 ± 136.5). No statistically significant difference in VEGF concentration was found between the COPD/tobacco and the COPD/post-TB subgroups (p = 0.59), but the concentration was higher in the COPD/tobacco subgroup compared to the control group (p = 0.035) and not statistically significant difference between the COPD/post-TB subgroup and the control group (p = 0.926) (Figure 11).
Concentration of other cytokines:
No statistically significant differences between the control group and the subgroups were found in the concentrations of other cytokines such as MCP-1, MIP-1α, IP-10, G-CSF and GM-CSF using the Student T-test.
Correlation between clinical stage, cells and cytokine levels in sputum The concentration of GRO and cells varied in the same direction with a statistically significant association between GRO and monocytes.A positive correlation was found between sCD40L and cells such as neutrophils and monocytes (r = 0.458 and r = 0.24 respectively) with p-values of 0.0001 and 0.042 respectively.The more advanced the clinical stage was, the higher the IL-1α and IL-1β concentrations were, with correlation coefficients of 0.473 and 0.466 respectively and p-values below 0.0001. Statistically significant positive correlations were also found between neutrophils levels and cytokines such as IL-1α and IL-1β.The more advanced the clinical stage was, the higher the concentrations of MIP-1α and IL-8 were (Table IV).