Trigger a variety of immunological responses with E. coli Lipopolysaccharide O55:B5 (S-form), a lipopolysaccharide (LPS) derived from the O55:B5 serotype of the Gram-negative bacteria and nbsp Escherichia coli. Composed of a lipid A, a core oligosaccharide, and an O antigen, LPS are glycolipid constituents that reside on the outer membranes of gram-negative bacteria (Kitchens RL et al.). LPS protects bacteria against bile salts and lipophilic antibiotics by maintaining the outer integrity of the cell membrane (Bäckhed F et al.). E. coli lipopolysaccharide O55:B5 (S-form), in particular, is predominantly recognized by toll-like receptor 4 (TLR4), which leads to the activation of NF-κβ, a protein complex which plays a key role in regulating immune response (Kuzmich N et al.). Activation of NF-κβ can trigger increased production of pro-inflammatory cytokines IL-1 and TNF-α by macrophages (Matuschak GM et al.). This LPS can also interact with CD14 to activate phospholipase Cγ2 and kinases of the Src family, trigger influxes of extracellular Ca2+, as well as calcineurin-dependent translocation of the nuclear factor of activated T cells (NFAT) family of transcription factors (Li CC et al.). When added to ImmunoCult™-SF macrophage medium (Catalog #10961), stimulation with lipopolysaccharide from E. coli (O55:B5) and IFN-γ supports the polarization to M1 (classically activated) macrophages. Warning: This product is highly pyrogenic. Avoid all means by which the product may enter the bloodstream.