Innate immunity against bacterial lipids is the front line of defense mechanisms and induces activation of various cells. Lipopolysaccharides (LPS), the component of the outer membrane of gram-negative bacteria, activate macrophages and other cells via the Toll-like receptor 4 (TLR4) /MD2 complex. Binding of different LPS and antagonists to the receptor is the key step for cell activation. Glycosphingolipids (GSL), the membrane component of Sphingomonas bacteria instead of LPS, are the natural ligand of natural killer T (NKT) cells that are stimulates by presentation as a complex of GSL and CD1d molecule. GSL-7, prepared from S. yanoikuyae, is the most potent natural ligand and heightens ability of defense mechanisms.Treatment with a-galactosylceramide before LPS challenge results in development of fetal shock through the activation of NKT cells. Among mycobacterial lipids, trehalose dimycolate (TDM) strongly activates macrophages to induce production of inflammatory cytokines via TLR2. Lipomannan and lipoarabinomannan, mannose-biding phosphatidylinositol, bind to not only TLR2 but also the mannose receptor expressed on macrophages. Glycopeptidolipids (GPL) are the sero-type specific component of Mycobacterium avium complex (MAC). Sero-type 4 GPL, but not sero-type 9 GSL, inhibits the phagosome/lysosome (PL) -fusion during phagocytosis of macrophages. Here, interaction of bacterial lipids with various cells will discuss.

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