Adjuvant activity in delayed hypersensitivity of the peptidic part of bacterial peptidoglycans.

Abstract

IT is generally accepted that the presence of killed mycobacteria in complete Freund's adjuvant is necessary to induce a typical delayed hypersensitivity to soluble antigens1 and attempts have been made to isolate the active component. The preparations obtained initially were of a peptidoglycolipidic nature2. Hydrosoluble adjuvants containing an arabinogalactan and the wall peptidoglycan have been isolated3–5. We have shown previously that the purified cell wall peptidoglycan of several Gram-negative bacteria exhibit the same adjuvant effect as mycobacteria for the induction of delayed hypersensitivity6,7 and that the disaccharide peptide monomer (β-1,4-N-acetylglucosaminyl-N-acetylmuramyl-L- diaminopimelic acid (L)-D-Ala) was still active8. Similar findings have been made independently with the peptidoglycan of mycobacteria9,10, the subunit structure of which is only slightly different: N-acetylmuramic acid is replaced by N-glycolylmuramic acid and both Glu and diaminopimelic acid residues have amide substituents. The present study was undertaken to determine to what chemical structure of the peptidoglycan adjuvant activity was related.