Endotoxin Activity Assay: A Chemiluminescence-Based Bioassay for Investigating Endotoxin Activity in Blood Sample

In Gram-negative bacteria, lipopolysaccharide endotoxins are vital components of the bacterial outer membrane.

Structurally, an endotoxin is comprised of the O-antigen - outermost polysaccharide chain connected via a central core to lipid A, an immunostimulatory glycolipid crucial for endotoxin activity.

To investigate endotoxin activity, take a test tube with a suitable buffer containing anti-lipid A antibodies, zymosan - an exogenous neutrophil activator, and luminol - a chemiluminescent agent.

Suspend an optimum volume of an infected blood sample comprising endotoxins and blood cells, including neutrophils. Incubate the tube under physiological conditions.

During incubation, anti-lipid A antibody recognizes the lipid-A component of the endotoxin and binds to it via antigen-binding domains, resulting in the formation of an antibody-endotoxin complex.

The endotoxin-bound antibody's FC domain binds to the neutrophils' complementary receptor, presenting the attached endotoxins to neutrophils. This binding acts as a priming stimulus for neutrophils, triggering their activation.

Activated neutrophils engulf the zymosan and initiate an immune response, resulting in a rapid release of r