Figure 3.1 Structure of Toll like receptor:

 

TLRs are found in the cell surface as well as inside the cells and hence are able to recognize a wide variety of antigens. TLR-1, -2, -4, -5 and -6 are expressed over the surface of plasma membrane while TLR-3, -7, -8, and -9 are expressed inside endosomal membrane (Figure 3.2). Different TLRs can recognize different antigens as listed below.

TLR-1 Bacterial lipoprotein

TLR-2 Bacterial peptidoglycans

TLR-3 Double stranded RNA

TLR-4 Lipopolysaccharides

TLR-5 Bacterial flagella

TLR-6 Bacterial lipoprotein

TLR-7 Single stranded RNA

TLR-8 Single stranded RNA

TLR-9 CpG DNA