Penguins (Sphenisciformes) are an iconic order of flightless, diving seabirds distributed across a large latitudinal range in the Southern Hemisphere. The extensive area over which penguins are endemic is likely to have fostered variation in pathogen pressure, which in turn will have imposed differential selective pressures on the penguin immune system. At the front line of pathogen detection and response, the Toll-like receptors (TLRs) provide insight into host evolution in the face of microbial challenge. TLRs respond to conserved pathogen-associated molecular patterns and are frequently found to be under positive selection, despite retaining specificity for defined agonist classes. We undertook a comparative immunogenetics analysis of TLRs for all penguin species and found evidence of adaptive evolution that was largely restricted to the cell surface-expressed TLRs, with evidence of positive selection at, or near, key agonist-binding sites in TLR1B, TLR4, and TLR5. Intriguingly, TLR15, which is activated by fungal products, appeared to have been pseudogenized multiple times in the Eudyptes spp., but a full-length form was present as a rare haplotype at the population level. However, in vitro analysis revealed that even the full-length form of Eudyptes TLR15 was nonfunctional, indicating an ancestral cryptic pseudogenization prior to its eventual disruption multiple times in the Eudyptes lineage. This unusual pseudogenization event could provide an insight into immune adaptation to fungal pathogens such as Aspergillus, which is responsible for significant mortality in wild and captive bird populations.

• Klíčová slova
• Toll-like receptors, avian immunology, host–pathogen interaction, immunogenetics, pseudogenization, wildlife disease,
• MeSH
• molekulární evoluce MeSH
• selekce (genetika) MeSH
• Spheniscidae * genetika   MeSH
• toll-like receptory genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• toll-like receptory MeSH

Toll-like receptors (TLRs) form a key component of animal innate immunity, being responsible for recognition of conserved microbial structures. As such, TLRs may be subject to diversifying and balancing selection, which maintains allelic variation both within and between populations. However, most research on TLRs in non-model avian species is focused on bottlenecked populations with depleted genetic variation. Here, we assessed variation at the extracellular domains of three TLR genes (TLR1LA, TLR3, TLR4) across eleven species from two passerine families of buntings (Emberizidae) and finches (Fringillidae), all having large breeding population sizes (millions of individuals). We found extraordinary TLR polymorphism in our study taxa, with >100 alleles detected at TLR1LA and TLR4 across species and high haplotype diversity (>0.75) in several species. Despite recent species divergence, no nucleotide allelic variants were shared between species, suggesting rapid TLR evolution. Higher variation at TLR1LA and TLR4 than TLR3 was associated with a stronger signal of diversifying selection, as measured with nucleotide substitutions rates and the number of positively selected sites (PSS). Structural protein modelling of TLRs showed that some PSS detected within TLR1LA and TLR4 were previously recognized as functionally important sites or were located in their proximity, possibly affecting ligand recognition. Furthermore, we identified PSS responsible for major surface electrostatic charge clustering, which may indicate their adaptive importance. Our study provides compelling evidence for the divergent evolution of TLR genes in buntings and finches and indicates that high TLR variation may be adaptively maintained via diversifying selection acting on functional ligand binding sites.

• Klíčová slova
• Allele diversity, Birds, Divergent evolution, Polymorphism, Positive selection, Toll-like receptors,
• MeSH
• ligandy MeSH
• molekulární evoluce MeSH
• Passeriformes * genetika   MeSH
• pěnkavovití * genetika   MeSH
• toll-like receptor 3 genetika   MeSH
• toll-like receptor 4 genetika   MeSH
• toll-like receptory genetika   chemie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• ligandy MeSH
• toll-like receptor 3 MeSH
• toll-like receptor 4 MeSH
• toll-like receptory MeSH

Balancing selection is a classic mechanism for maintaining variability in immune genes involved in host-pathogen interactions. However, it remains unclear how widespread the mechanism is across immune genes other than the major histocompatibility complex (MHC). Although occasional reports suggest that balancing selection (heterozygote advantage, negative frequency-dependent selection, and fluctuating selection) may act on other immune genes, the current understanding of the phenomenon in non-MHC immune genes is far from solid. In this review, we focus on Toll-like receptors (TLRs), innate immune genes directly involved in pathogen recognition and immune response activation, as there is a growing body of research testing the assumptions of balancing selection in these genes. After reviewing infection- and fitness-based evidence, along with evidence based on population allelic frequencies and heterozygosity levels, we conclude that balancing selection maintains variation in TLRs, though it tends to occur under specific conditions in certain evolutionary lineages rather than being universal and ubiquitous. Our review also identifies key gaps in current knowledge and proposes promising areas for future research. Improving our understanding of host-pathogen interactions and balancing selection in innate immune genes are increasingly important, particularly regarding threats from emerging zoonotic diseases.

• Klíčová slova
• TLR, Toll-like receptors, balancing selection, host–pathogen interactions, innate immune genes, polymorphism,
• MeSH
• frekvence genu MeSH
• hlavní histokompatibilní komplex MeSH
• polymorfismus genetický * MeSH
• přirozená imunita genetika   MeSH
• selekce (genetika) MeSH
• toll-like receptory * genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• toll-like receptory * MeSH

Sjögren's syndrome (SS) is a chronic autoimmune immunopathological disease of unknown aetiology. It is characterized by focal lymphocyte infiltration and inflammation in exocrinne glands, involving especially salivary and lacrimal glands. Hypofunction of the glands leads to the decreased glandular secretion together with impaired production of saliva and tears, resulting in dryness of the mouth and eyes (xerostomia and xerophthalmia, respectively). Some of the studies have suggested that Toll-like receptors and B cells play a pivotal role in the pathogenesis of autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis and SS etc. Stimulation of B cells via the TLRs pathway leads to several important changes including increase in antibody production, differentiation to plasma cells, cytokine production and up-regulation of molecules essential for antigen presentation to (autoreactive) T cells. Experimental data support the idea that co-engagement of BCR and TLR might be sufficient for B cell activation and lead to the failure of tolerance. In human naive B cells, most TLRs are expressed at very low or undetectable level, but expression of TLR 7 and 9 is rapidly induced by B cell receptor triggering. This review will focus on the possible role of B cells and TLRs signaling in the pathogenesis of SS.

• MeSH
• autoimunita imunologie   MeSH
• B-lymfocyty imunologie   MeSH
• lidé MeSH
• Sjögrenův syndrom imunologie   patofyziologie   MeSH
• toll-like receptory imunologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• toll-like receptory MeSH

The innate immune system senses invading microorganisms by a phylogenetically conserved family of proteins PRRs of which TLRs are ones of the most important. There are at least 10 different TLRs in humans and 11 in mice. They have in the course of evolution specialized for the recognition of conserved structures among microorganisms called PAMPs. Activation of TLRs results in induction of innate immunity mechanisms as well in development of antigen-specific adaptive immune responses, thus bridging innate and adaptive immunity.

• MeSH
• biologické modely MeSH
• intracelulární signální peptidy a proteiny MeSH
• lidé MeSH
• ligandy * MeSH
• myši MeSH
• přirozená imunita MeSH
• signální transdukce MeSH
• toll-like receptor 2 metabolismus   MeSH
• toll-like receptor 4 imunologie   metabolismus   MeSH
• toll-like receptory chemie   metabolismus   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• intracelulární signální peptidy a proteiny MeSH
• ligandy * MeSH
• toll-like receptor 2 MeSH
• toll-like receptor 4 MeSH
• toll-like receptory MeSH

Various stressors including temperature, environmental chemicals, and toxins can have profound impacts on immunity to pathogens. Increased eutrophication near rivers and lakes coupled with climate change are predicted to lead to increased algal blooms. Currently, the effects of cyanobacterial toxins on disease resistance in mammals is a largely unexplored area of research. Recent studies have suggested that freshwater cyanotoxins can elicit immunomodulation through interaction with specific components of innate immunity, thus potentially altering disease susceptibility parameters for fish, wildlife, and human health owing to the conserved nature of the vertebrate immune system. In this study, we investigated the effects of three microcystin congeners (LR, LA, and RR), nodularin-R, and cylindrospermopsin for their ability to directly interact with nine different human Toll-like receptors (TLRs)-key pathogen recognition receptors for innate immunity. Toxin concentrations were verified by LC/MS/MS prior to use. Using an established HEK293-hTLR NF-κB reporter assay, we concluded that none of the tested toxins (29-90 nM final concentration) directly interacted with human TLRs in either an agonistic or antagonistic manner. These results suggest that earlier reports of cyanotoxin-induced NF-κB responses likely occur through different surface receptors to mediate inflammation.

• Klíčová slova
• Cyanotoxin, Inflammation, NF-κB, Toll-like receptor,
• MeSH
• alkaloidy MeSH
• cyklické peptidy MeSH
• HEK293 buňky MeSH
• lidé MeSH
• mikrocystiny * toxicita   MeSH
• tandemová hmotnostní spektrometrie * MeSH
• toll-like receptory genetika   MeSH
• toxiny kmene Cyanobacteria MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• alkaloidy MeSH
• cyklické peptidy MeSH
• cylindrospermopsin MeSH Prohlížeč
• mikrocystiny * MeSH
• nodularin MeSH Prohlížeč
• toll-like receptory MeSH
• toxiny kmene Cyanobacteria MeSH

The onset of IgA nephropathy (IgAN), characterized by glomerular deposition of IgA-containing immune complexes, is often associated with synpharyngitic hematuria. Innate immune responses mediated by Toll-like receptors (TLR) may play a role in IgAN onset and/or progression. Here, we assessed the expression of TLR 4, 7, 8, and 9 in renal-biopsy specimens from patients with IgAN, with different degree of proteinuria and eGFR, compared with normal-kidney and disease-control tissues (ANCA-associated vasculitis). Renal-biopsy specimens from 34 patients with IgAN and 7 patients with ANCA-associated vasculitis were used. In addition, we used 15 healthy portions of renal-tissue specimens from kidneys after nephrectomy for cancer as control specimens. Expression of TLR 4, 7, 8, and 9 was assessed using immunohistochemical staining of paraffin-embedded renal-biopsy tissue specimens with specific antibodies and evaluated semiquantitatively by light microscopy. Linear discriminant analysis (LDA) was used to test whether intrarenal staining of TLR 4, 7, 8, and 9 distinguished patients with IgAN from controls or correlated with eGFR and/or proteinuria. eGFR was calculated using the creatinine-based formula. Moreover, the biopsies from patients with IgAN were scored according to the Oxford Classification. LDA showed that staining for TLR 4, 7, 8, and 9 was more intense in specimens from IgAN patients compared to normal kidney tissues. The intensity of intrarenal staining of TLRs discriminated four groups of IgAN patients with different eGFR and proteinuria and MEST scoring.

• Klíčová slova
• ANCA-associated vasculitis, IgA nephropathy, Renal biopsy, Renal insufficiency, Toll-like receptors,
• MeSH
• hodnoty glomerulární filtrace MeSH
• IgA nefropatie komplikace   metabolismus   patologie   MeSH
• lidé MeSH
• studie případů a kontrol MeSH
• stupeň závažnosti nemoci MeSH
• toll-like receptory metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• toll-like receptory MeSH

The innate immune system senses invading microorganisms by a phylogenetically conserved family of proteins--TLRs. They are expressed in several types of cells that represent a route of entry of pathogens into the host organism and that can contribute to protection against infection. Except for cells of the immune system, TLRs are present in epithelial cells of the skin, respiratory, intestinal, and genitourinary tracts that form the first protective barrier to invading pathogens. Polarized regulation of TLR expression in epithelial cells explains why pathogenic but not commensal bacteria elicit inflammatory responses. TLR-induced intracellular signalling pathways show remarkable complexity: apart from a common signalling pathway, additional signalling pathways specific for each of the TLRs are responsible for a fine tuning of the immune response, thus securing effective pathogen-directed biological responses.

• MeSH
• adaptorové proteiny signální transdukční fyziologie   MeSH
• biologické modely MeSH
• lidé MeSH
• ligandy MeSH
• toll-like receptory fyziologie   MeSH
• transkripční faktory fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• adaptorové proteiny signální transdukční MeSH
• ligandy MeSH
• toll-like receptory MeSH
• transkripční faktory MeSH

Toll-like receptors (TLRs) represent an important part of the innate immune system. While human and murine TLRs have been intensively studied, little is known about TLRs in non-model species. The order Perissodactyla comprises a variety of free-living and domesticated species exposed to different pathogens in different habitats and is therefore suitable for analyzing the diversity and evolution of immunity-related genes. We analyzed TLR genes in the order Perissodactyla with a focus on the family Equidae. Twelve TLRs were identified by bioinformatic analyses of online genomic resources; their sequences were confirmed in equids by genomic DNA re-sequencing of a panel of nine species. The expression of TLR11 and TLR12 was confirmed in the domestic horse by cDNA sequencing. Phylogenetic reconstruction of the TLR gene family in Perissodactyla identified six sub-families. TLR4 clustered together with TLR5; the TLR1-6-10 subfamily showed a high degree of sequence identity. The average estimated evolutionary divergence of all twelve TLRs studied was 0.3% among the Equidae; the most divergent CDS were those of Equus caballus and Equus hemionus kulan (1.34%) in the TLR3, and Equus africanus somaliensis and Equus quagga antiquorum (2.1%) in the TLR1 protein. In each TLR gene, there were haplotypes shared between equid species, most extensively in TLR3 and TLR9 CDS, and TLR6 amino acid sequence. All twelve TLR genes were under strong negative overall selection. Signatures of diversifying selection in specific codon sites were detected in all TLRs except TLR8. Differences in the selection patterns between virus-sensing and non-viral TLRs were observed.

• Klíčová slova
• Equid, Innate immunity, Odd-toe ungulates, Toll-like receptor, Transpecies haplotype sharing,
• MeSH
• Equidae MeSH
• fylogeneze MeSH
• genomika MeSH
• koně genetika   MeSH
• lidé MeSH
• myši MeSH
• Perissodactyla metabolismus   MeSH
• toll-like receptor 1 * genetika   MeSH
• toll-like receptor 3 * MeSH
• toll-like receptory genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• toll-like receptor 1 * MeSH
• toll-like receptor 3 * MeSH
• toll-like receptory MeSH

Toll-like receptors (TLRs) are key sensor molecules in vertebrates triggering initial phases of immune responses to pathogens. The avian TLR family typically consists of ten receptors, each adapted to distinct ligands. To understand the complex evolutionary history of each avian TLR, we analyzed all members of the TLR family in the whole genome assemblies and target sequence data of 63 bird species covering all major avian clades. Our results indicate that gene duplication events most probably occurred in TLR1 before synapsids diversified from sauropsids. Unlike mammals, ssRNA-recognizing TLR7 has duplicated independently in several avian taxa, while flagellin-sensing TLR5 has pseudogenized multiple times in bird phylogeny. Our analysis revealed stronger positive, diversifying selection acting in TLR5 and the three-domain TLRs (TLR10 [TLR1A], TLR1 [TLR1B], TLR2A, TLR2B, TLR4) that face the extracellular space and bind complex ligands than in single-domain TLR15 and endosomal TLRs (TLR3, TLR7, TLR21). In total, 84 out of 306 positively selected sites were predicted to harbor substitutions dramatically changing the amino acid physicochemical properties. Furthermore, 105 positively selected sites were located in the known functionally relevant TLR regions. We found evidence for convergent evolution acting between birds and mammals at 54 of these sites. Our comparative study provides a comprehensive insight into the evolution of avian TLR genetic variability. Besides describing the history of avian TLR gene gain and gene loss, we also identified candidate positions in the receptors that have been likely shaped by direct molecular host-pathogen coevolutionary interactions and most probably play key functional roles in birds.

• Klíčová slova
• adaptive evolution, amino acid physicochemical properties, convergence, pattern recognition receptors, positive selection, pseudogene,
• MeSH
• duplikace genu * MeSH
• molekulární evoluce * MeSH
• pseudogeny MeSH
• ptáci genetika   MeSH
• sekvence aminokyselin MeSH
• selekce (genetika) * MeSH
• toll-like receptory genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• srovnávací studie MeSH
• Názvy látek
• toll-like receptory MeSH