Immunostimulation with bacterial phospholipid extracts.

Injection of bacterial phospholipid extracts (EBP) into mice increased their resistance towards a Listeria monocytogenes infection. The blood clearance of virulent Salmonella typhimurium was enhanced and the degree of clearance correlated with the dose of extract injected. The multiplication of Listeria monocytogenes in spleen and liver of mice was inhibited and this inhibition was also correlated with the amount of extract injected. The absence of apparent toxicity in mice, of splenoand hepatomegaly, and of lymphoid hyperplasia, distinguish this immunostimulant from other known bacterial stimulants of host resistance to infection.