[Chemical structure of mycobacterial cell wall]

The immunostimulant properties of mycobacterial cell walls have led to a thorough study of their structure and to isolation of their components. The backbone of the mycobacterial cell wall is of a covalent structure ("covalent skeleton") made up of two polymers covalently linked by phosphodiester linkages: a arabinogalactan mycolate and a peptidoglycan. To this covalent structure are attached, in a rather ill defined manner, proteins or lipoproteins and, in pathogenic and most vaccinating strains, a partly amidated poly-alpha-L-glutamic acid. The mycobacterial cell wall also contains about 25% of free lipids, i.e. lipids which can be extracted by neutral solvents.