Toll-like receptors in domestic animals

Abstract

Toll-like receptors are pattern recognition receptors with which hosts recognize pathogen-associated molecular patterns (PAMP). This recognition process is translated rapidly into a meaningful defense reaction. This form of innate host defense is preserved in the animal kingdom: invertebrates heavily depend on it; higher vertebrates also have an adaptive immune system. Both adaptive and innate immune systems are intertwined in that the former also depends on an intact innate recognition and response system. Members of the TLR system cover recognition of parasitic, bacterial or viral germs. Due to the constraints imposed by the necessity to recognize PAMP and to interact with downstream signaling molecules, the TLR system is relatively conserved in evolution. Nevertheless, subtle species differences have been reported for several mammalian TLR members. Examples of this will be given. In all mammalian species investigated, part of the coding sequence is available for the most important TLR members, thus allowing study of expression of these TLR members in various tissues by reverse-transcription polymerase chain reaction in its classical (RT-PCR) and quantitative real time RT-PCR (qRT-PCR) form. In some species, the whole coding sequences of the most important or even all TLR members are known. This allows construction of cDNA and transfection of common host cells, thus permitting functional studies. Extensive investigations were devoted to the study of non-synonymous single nucleotide polymorphisms. In a few cases, expression of a given amino acid in the extracellular (ligand-binding) portion of TLR members could be associated with infectious diseases. This will be discussed below.

Determination of Genetic Variations of Toll-like Receptor (TLR) 2, 4 and 6 with Next Generation Sequencing in Native Cattle Breeds of Anatolia and Holstein Friesian

“…This is an important observation, as those bacterial diseases to which Anatolian breeds have been described to be more resistant are mainly caused by bacteria binding to TLR2 [38]. Analyzing the identified SNPs in TLR2 in more detail, one aa change was identified in LRR1-10, four between LRR11-LRR20, one in the TM, and four in the TIR domains, respectively, in native cattle breeds whereas only one was determined in LRR5…”

Mannose Receptor Ligands Regulate the Gene Expression of Toll-like Receptors in Chicken Monocytes

“…Several classes of PRRs recognize various PAMPs, of which C-type lectin receptors and TLRs are likely very important Jungi et al, 2011). NO is an important pro-inflammatory mediator that is involved in macrophage activities against intracellular pathogenic microorganisms and viral proliferation.…”

“…These structures are generally known as pathogen-associated molecular patterns (PAMPs), and the receptors that recognize them are pattern recognition receptors (PRRs) (Murphy K et al, 2008). Many receptors have been implicated in pattern recognition, including the mannose receptor (MR), NODlike receptors, Dectin-1, DC-SIGN and Toll-like receptors (TLRs) (Dostert et al, 2008;Ip et al, 2009;Reid et al, 2009Jungi et al, 2011Kumagai et al, 2008;Mathews et al, 2008;Meylan et al, 2006).…”

“…The best studied candidates for cooperation with MR are the Toll-like receptors (TLRs), which are a family of evolutionarily conserved PRRs that play a critical role in initiating innate immune responses and activating antigen-specific adaptive immunity. Ten TLR family members have been identified in chickens, and each recognizes and responds to different microbial components (He et al, 2006a;2006b;Jungi et al, 2011).…”

Involvement of TLR7 and TLR8 in conceptus development and establishment of pregnancy in sheep

“…Of the 13 TLRs identified in mammals (Hansen et al 2011, Jungi et al 2011, ten are known to be expressed in domestic ruminants (Menzies & Ingham 2006, Chang et al 2009), which display high homology with their human counterparts (Nalubamba et al 2007, Tirumurugaan et al 2010. Besides TLR10, for which no function has been established, TLR ligand specificity depends on cellular location with some being expressed on the cell surface (TLR1, TLR2, TLR4, TLR5, and TLR6) for recognition of bacterial and fungal compounds, and others being localized to the endosomal compartment (TLR3, TLR7, TLR8, and TLR9), where they mainly bind nucleic acids from viral pathogens , Kumar et al 2009).…”