Immunomodifiers of bacterial origin.

A number of compounds have been isolated from bacteria able to induce immunomodulation. Among them, Lipopolysaccharide (LPS) and the active structure Lipid A are presented here as a model. In addition, other natural compounds among the best defined are briefly described. The knowledge of these chemical structures has now opened the field for synthetic compounds, allowing the preparation of related derivatives and the study of structure-activity relationship. Lipid A analogs are currently under investigation. Muramyldipeptide which was described as the smallest compound capable of substituting for mycobacteria in Freund complete adjuvant has been synthesized. A number of muramylpeptides are endowed with adjuvant, anti-infectious, anti-tumoral properties without inducing side-effects. So, compounds of bacterial origin constitute a promising source for potentiation of the immune system.