Further studies on bacterial lipopolysaccharide-induced protection against experimental allergic encephalomyelitis in guinea pigs. Effects of chemical modifications.

Bacterial lipopolysaccharide (LPS)-induced protection against experimental allergic encephalomyelitis (EAE) was studied in guinea pigs using chemically modified derivatives. Hydroxylaminolysis or alkaline hydrolysis of LPS, by which ester-linked fatty acids are removed from LPS, resulted in total loss of its mitogenic activity for B lymphocytes, and EAE-suppressive activity was simultaneously reduced. Similar diminished activity was observed in delayed-type skin reactions to myelin basic protein (BP) and anti-BP antibody production detected by passive hemagglutination and enzyme-linked immunosorbent assay (ELISA). These results indicate that the active site of LPS in suppressing EAE is in the lipid portion and that there exists a good correlation between the capacity of LPS to suppress EAE and its mitogenic activity.