Toll like receptors (TLRs) are a class of proteins, which play an important role in the innate immune system. They are usually single, they usually span the entire membrane and are expressed on sentinel cells such as dendritic cells and macrophages, which recognize structurally conserved molecules derived from microbes. When the microbe breaches the physical barriers of the body like skin or intestinal mucosa, the TLRs recognize them and initiate an immune response. The TLRs include TLR1, TLR2, TLR3, TLR4, TLR5, TLR6, TLR7, TLR8, TLR9, TLR10, TLR11, TLR12 and TLR13, of which TLR12 and 13 are not found in humans. TLRs received their name from their similarity to the protein coded by toll gene in Drosophila in the year 1985 by Christiane Nusslein-Volhard.
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TLR5: Flagellin.
TLR6: Bacterial lipopeptides.
TLR7: Imiquimod (Aldara), R848
TLR8: R848 (Resiquimoid)
TLR9: CpG DNA
TLR10: unknown
FUNCTIONS OF TLRs
Our immune system’s ability to distinguish between different molecules that are shared by different pathogens is due to the presence of immune receptors in cell known as toll-like receptors (TLRs), that are expressed on the surface of the Antigen presenting cells like dendritic cells, macrophages, natural killer cells etc.
Upon activation, TLRs recruit adapter proteins within the cytosol of the immune cell to propagate antigen induced signal transduction pathway. The recruited adaptor proteins are responsible for the activation of other like protein kinases etc. which further amplifies the signal and may lead to upregulation or suppression of genes which control inflammatory responses and other transcriptional activities. These events may lead increase or decrease of cytokine production, proliferation, and survival, while others lead to greater adaptive immunity. If the ligand is from a bacterial factor, the pathogen might be phagocytosed and digested. If it’s a viral factor the infected cell may undergo
TLR5: Flagellin.
TLR6: Bacterial lipopeptides.
TLR7: Imiquimod (Aldara), R848
TLR8: R848 (Resiquimoid)
TLR9: CpG DNA
TLR10: unknown
FUNCTIONS OF TLRs
Our immune system’s ability to distinguish between different molecules that are shared by different pathogens is due to the presence of immune receptors in cell known as toll-like receptors (TLRs), that are expressed on the surface of the Antigen presenting cells like dendritic cells, macrophages, natural killer cells etc.
Upon activation, TLRs recruit adapter proteins within the cytosol of the immune cell to propagate antigen induced signal transduction pathway. The recruited adaptor proteins are responsible for the activation of other like protein kinases etc. which further amplifies the signal and may lead to upregulation or suppression of genes which control inflammatory responses and other transcriptional activities. These events may lead increase or decrease of cytokine production, proliferation, and survival, while others lead to greater adaptive immunity. If the ligand is from a bacterial factor, the pathogen might be phagocytosed and digested. If it’s a viral factor the infected cell may undergo