SAA2 and Sepsis: Differential analysis identified 6 proteins that were significantly upregulated in sepsis serum samples, including MMP9, lipocalin-2 (LCN2), serum amyloid A1 (SAA1), serum amyloid A2 (SAA2), paired-like homeobox 2B (PHOX2B), and lactoferrin (LTF) (|log2FC| > 1, P < 0.05) (Fig. 3E).