Lipopolysaccharides

Lipopolysaccharides (LPS) also known as lipoglycans and endotoxins are large molecules found on the outer membrane of gram-negative bacteria. They provoke a strong innate immune response. LPS is an exogenous pyrogen.

One study found higher levels of serum IgA and IgM against LPS in chronic fatigue syndrome patients, indicating bacterial translocation from the intestine into the bloodstream. . Serum IgA was significantly correlated to the severity of illness.

A study of 128 ME/CFS patients found significantly increased IgA response to lipopolysaccharides (LPS) from the cell walls of commensal bacteria. Increased IgA response was associated with increased serum IL-1, TNFα, neopterin and elastase. The study concluded that increased translocation of commensal bacteria may be responsible for the disease activity in some ME/CFS patients.

A study of 48 ME/CFS patients and 39 controls in 2016 found elevated levels of LPS in patients.

Some LPS molecules have been implicated in autoimmune disease including multiple sclerosis and Guillain-Barré syndrome.

A study in 2000 found that direct electrical stimulation of the vagus nerve in rats decreased the inflammatory response to LPS.