Peptidoglycan is an essential cell wall component of virtually all bacteria. Peptidoglycan is a polymer of Nacetylglucosamine and N-acetylmuramic acid, crosslinked by short peptides. Breakdown products of peptido glycan are recognized by diff erent classes of pattern-recognition receptors [19] . Polymeric soluble peptidoglycan is recognized by TLR2 on the surface of cells, and the interaction of peptidoglycan with TLR2 triggers MyD88-dependent activation and nuclear translocation of NF-κB, and subsequently the transcription and secretion of cytokines. Muramyl dipeptide and γ-Dglutamyl-meso-diaminopimelic acid, which are lowmolecular weight breakdown fragments of peptidoglycan, are recognized by intracellular pathogen recognition receptors, nucleotide-binding oligomerization domain containing (Nod)2 and Nod1, respectively [19] . Ligand binding to these receptors triggers interaction with the receptor-interacting protein kinase, RIP2, which activates NF-κB. Of these peptidoglycan breakdown products, only polymeric peptidoglycan binds to CD14, and CD14 enhances polymeric peptidoglycan-induced TLR2 activation. Th e low molecular weight fragments of peptidoglycan, like muramyl dipeptide, do not bind to CD14, do not induce cell activation through CD14 and also do not interfere with the binding of polymeric peptidoglycan to CD14 [19] . Furthermore, unlike LPS, peptidoglycan bound to sCD14 is not able to activate epithelial and endothelial cells with low membrane CD14 expression.