MD-2 is co-expressed with TLR4 on the cell membrane of various cell types including leukocytes and endothelium (11, 19, 20), but soluble MD-2 (sMD-2) is elevated in plasma from patients with inflammatory conditions, such as sepsis, HIV infection, and endotoxemia (21–23). Here, LY96 is linked to serum lipopolysaccharide activity.