FCGR2A and chronic obstructive pulmonary disease: Direct comparisons of female vs. male COPD patients was performed using OPLS-DA analysis, yielding 119 significant proteins (R2 = 0.92, Q2 = 0.86, p[CV-ANOVA] = 4.6 × 10−7) representing 7 significant pathways (p < 0.05), including oxidative phosphorylation, FcγR-mediated phagocytosis, lysosome and citrate cycle (Additional file 2: Table S4).