Endotoxin-induced auto-immunity in mice. III. Comparison of different endotoxin preparations

Six different endotoxin preparations derived from Escherichia coli and Salmonella typhimurium subspecies were compared as to their potencies to provoke auto-immune phenomena in mice. The numbers of spleen cells forming antibodies to bromelain-treated isologous erythrocytes or anti-DNA antibodies, the serum levels of these auto-antibodies, and the circulating immune complex titres were determined. As far as comparison on a weight base was concerned, S. typhimurium Re-mutant lipopolysaccharide appeared to be the most active preparation in inducing auto-antibody formation. Upon comparison of amounts with equal activity in the limulus amoebocyte lysate assay, however, S. typhimurium lipid A turned out to be the most potent. The contribution of O-type specific polysaccharides, phosphate groups, and the lipid A moiety to the potencies of the endotoxin preparations is discussed.