Fig. 4
Regression analysis performed in all COPD patients (a–d) showing significant positive correlations. There is a significant positive correlation between the number of plasma cells/mm2 in the lamina propria and total IgA scored in the lamina propria (a) and secreted IgA scored in the epithelium (b). Plasma cells/mm2 in the lamina propria were also significantly correlated with number of neutrophils (c) and pIgR scored in the lamina propria (d). Correlation coefficients were calculated using the Spearman rank method