TLR2 is involved in recognition of peptidoglycan from gram-positive bacteria, bacterial lipoproteins, mycoplasma lipoprotein and mycobacterial products. It is quite possible that recognition of at least some other TLR2 ligands may be assisted by additional accessory proteins, particularly in association with TLR1 or TLR6. TLR2 is expressed constitutively on macrophages, dendritic cells, and B cells, and can be induced in some other cell types, including epithelial cells. TLR1 and TLR6, on the other hand, are expressed almost ubiquitously (Muzio et al. 2000). TLR2 may be a sensor and inductor of specific defense processes, including oxidative stress and cellular necrosis initially spurred by microbial compounds.