CAT and bacterial infectious disease: Among the proteins upregulated in the pneumonia cohort were mainly proteins involved for leucocyte and neutrophil activation and general response to bacterial infection (e.g. lysozyme C (LYZ), bactericidal permeability-increasing protein (BPI), peptidoglycan recognition protein 1 (PGLYRP1) and others), as well as oxidative stress defence (e.g. catalase (CAT), peroxiredoxin-1 (PRDX1), Myeloperoxidase (MPO); (Additional file 6: Table S5).