| Summary: | Lipopolysaccharide (LPS), also known as endotoxin, is a constituent of the outer membrane of gram-negative bacteria which is toxic for humans and other animals. LPS probably plays a key part in the pathogenesis of Gram-negative bacteraemia and sepsis syndrome in humans. Cross-reactive antibodies to LPS may play a part in natural host defences, and may also be useful in the treatment of Gram-negative bacteraemia and sepsis syndrome. The structure of LPS, its toxicity, its role in Gram-negative bacteraemia and sepsis syndrome in humans, and the potential value of cross-reactive antibodies to LPS are reviewed. The antibody response in recipients of typhoid vaccine was studied, with particular reference to the possibility that typhoid vaccine might induce the production of antibodies to the core region of LPS (LPS-core). In most recipients however the response observed was directed against specific antigens. Urine samples from patients with suspected UTI were tested for IgG antibodies to LPS-core. Such antibodies were found to be associated with the presence of bacteriuria, although the association was not strong enough for antibody assay to be useful as a diagnostic test. Total urinary IgG was equally strongly associated with bacteriuria. This suggested that the antibodies were probably present because of non-specific leakage of serum components into the urine as a result of inflammation. A large number of murine monoclonal antibodies (MAbs) to LPS-core had been produced by a collaborative group in Edinburgh and Basel, in the hope of producing a cross-reactive MAb which would be useful therapeutically. The binding of some of these MAbs to a collection of blood-culture isolates of Gram-negative bacteria was studied.
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