Lipid A, mAb 26-5

The monoclonal antibody 26-5 recognizes lipid A. The lipid A domain of lipopolysaccharide (LPS) is a
unique, glucosamine-based phospholipid that makes up the outer monolayer of the outer membrane of
most gram-negative bacteria.
Lipid A is responsible for the endotoxic activities of LPS, and a heteropolysaccharide. The
heteropolysaccharide generally consists of an oligosaccharide termed the core region. This core region
is in some bacterial families composed of repeating oligosaccharide units, the so-called O chain. The
lipid A moiety of LPS is detected by the TLR4/MD2 receptor of the mammalian innate immune system.
Picomolar levels of lipid A induce macrophages to synthesize potent mediators of inflammation, such as
TNF-α and IL-1β. Furthermore, lipid A activates the production of costimulatory molecules required for
adaptive immunity and stimulates tissue factor production in mononuclear and endothelial cells. All
these events are desirable for clearing local infections.