| TLR | Physiological Function | Target (ligand) Molecules | Target (micro) Organism | Co-Receptors |
| TLR1 | Sensing of bacterial lipopeptides | Tripalmytated lipopetide (Triacetylated lipoproteins) | Mycobacterium tuberculosis [89] Borrelia Burgdorferi [90] |
TLR2 [90] |
| TLR2 | Sensing the antigen, Enhancement of inflammatory response, depletion of IRAK1 and subsequent inhibition of type 1 IFNs secretion in viral infection | Tripalmytated lipopeptides, lipoteichoic acid, peptiglycan bacterial, mycoplasma lipoprtoeins, lipoarabinomannan of mycobacterium, soluble modulin from staph epidermidis, zymosan of yeast wall glycosylphosphatidyl inositol, viral lipoprotein and glycoproteins Alarmins ( product of cell destruction, apoptosis, necrosis and tumor cells) | Gram positive and negative bacteria, mycobacterium Mycoplasma [91], hepatitis B and C virus | MYD88, TIRAP |
| TLR3 | dS RNA, viral antigens and Apoptotic derived RNA | Endosomal, senses endocytosed exogenous viral dSRNA, Poly I:C (Polyribinosic:polyribocytidylic, extracellular in certain cells [92] | Viruses e.g. positive strand RNA virus polio, coxakie encephalomyocarditis virus, HIV gag mRNA, Epithelial TLR3 in Sjogren syndrome [93]. | Cytoplasmic domain dimerization, downstream activation through TICAM-1 [92] |
| TLR4 | Bacterial lipopolysaccharide sensing , Free fatty acids, | LPS lipid A consist of glucosamine, acyl chain (FA residue) carbon chain length of 10-16 [94,95] FFA chain of 12 Laurate or 16 palmitate [95] |
Gram negative bacteria, endogenous fatty acid from apoptosis of adipose tissue Contribute to obesity associated inflammation and metabolic syndrome [7] | CD14, MyD88 [94], IRAK(IL-1 associated Kinase), TRAF 6 |
| TLR5 | Flagelin [96] Mucosal protection of intestine, airway urogenital and eye, distinct response to different bacteria including antiapoptotic activation | Flagelin monomere | All intestinal bacteria containing flagelin, 15000 different species with a 2X 10 6 distinct genes. Responding according to the bacterial toxicities | MyD88 Flagelin Ipaf/ Naip 5 in macrophages inflammome |
| TLR6 | A sensing and responding to a certain categories of bacteria, protozoan, and viruses after heterodimerization with TLR2. Soluble TLR2 has modulating effect on TLR2 anchored to cells | MALP2 (mycoplasmal macrophage-activating lipoprotein), molecules with Diacylglycerol, triacylglycerol moities | Mycoplasma Gram positive bacteria [97] Cryptoccocus neoforman , Candida albicans Saccharomyces Cerevisiae Entamaeba histolytica, cytomegalovirus, Hepatitis C, Measles, herpes simplex, respiratory cynstial virus [9] | MyD88CD14, CD36, TIRAP RP 105, by decreasing the threshold of the concentration needed for recognition and signaling |
| TLR7 | Sensing of intracellular ribonucleotide and in certain circumstances extracellular receptor mediated | Oligoribonucleotide, rich in adenosine and uracil | Endocellular oligonucleotide from debris of apoptosis, viral single stranded RNA derived from viral RNA's, (after uncoating of viral RNA genome, contribute to autoimmune disease | Unc93b1 a 12 pass integral membrane protein on Endoplasmic Reticulum. with TLR9 traffic through the Golgi [98] apparatus to become endosome [10] |
| TLR9 | Sensing of intracellular deoxynucleotide | Non-methylated deoxynucelotide rich in cytosine-guanine | Intracellular DNA virus e.g herpes simplex, can distinguish 2 CpG motif. Recognition of Chromatin fragment to protect against autoimmune disease | Unc93b1, MyD88, TLR9 dimer in endosomal compartment that enable signaling [98] |