Lipoarabinomannan (LAM)

Lipoarabinomannan is a lipoglycan and major virulence factor in the bacteria genus Mycobacterium. In addition to serving as a major cell wall component, it is thought to serve as a modulin with immunoregulatory and anti-inflammatory effects. This allows the bacterium maintain survival in the human reservoir by undermining host resistance and acquired immune responses. These mechanisms include the inhibition of T-cell proliferation and of macrophage microbicidal activity via diminished IFN-γ response.  Additional functions of lipoarabinommanan are thought to include the neutralization of cytotoxic oxygen free radicals produced by macrophages, inhibition of protein kinase C, and induction of early response genes. Lipoarabinomannan is synthesized via addition of mannose residues to phosphoinositol by a series of mannosyltransferases to produce PIMs and lipomannan(LM).