Muramyl peptides are fragments of peptidoglycan from the cell walls of bacteria.  The immune system recognizes that muramyl peptides (containing two or more muramic acid groups) are products of bacteria and responds by becoming activated to resist infection.  This resistance to infection is nonspecific, and extends to unrelated species of bacteria, fungi, and viruses.  A key mechanism of the resistance to infection is activation of macrophages.  Macrophage activation results in increased production of microbicidal oxygen radicals such as superoxide and peroxide, and increased secretion of inflammatory cytokines.  These physiological responses also aid in combating infection.  Muramyl peptides activate macrophages and other cells of the immune system.  Muramyl peptides and similar agents will become more important in the future due to increasing resistance of microbes to antibiotics, and increasing numbers of patients with immunodeficiencies.¹

Muramyl polysaccharide-glycan complex (MPGC), a non-toxic bacterial cell wall extract contains muramic acid moieties attached to variable-length mannose-rich polysaccharides.  The mannose-rich polysaccharides promote internalization of the entire muramic acid-containing complex.  Once internalized, the muramic acid moieties of the MPGC activate the macrophages.  MPGC has also been shown to increase human lymphocyte proliferation, and significantly increase the production of human antigen-presenting dendritic cells in vitro.²

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