Peptidoglycan adjuvants: minimal structure required for activity.

The chemical structure of the adjuvant active fraction of mycobacterial cell walls has been investigated. It had been shown previously that soluble peptidoglycan fragments obtained from cell walls of Mycobacteria by lysozyme digestion or by other treatments act as adjuvants for increasing both humoral and cellular immunity. We then found that even the monomer subunit of the peptidoglycan of Mycobacteria (i.e. a disaccharide-tetrapeptide) is adjuvant active; then, similar compounds from other strains of bacteria were tested; the monomeric subunits of meso-diaminopimelic acid as well as L-lysine containing peptidoglycans were found to be adjuvant active. The smallest active compound studied so far is N-acetyl-muramyl-L-alanyl-D-isoglutamine synthesized for us by SINAY et al. (1975).