International Journal of Molecular Veterinary Research, 2024, Vol.14, No.6, 244-253 http://animalscipublisher.com/index.php/ijmvr 247 3.2 Impact of domestication on immune gene diversity Domestication has had a profound impact on the immune gene diversity of dogs compared to their wild counterparts. The process of domestication, characterized by population bottlenecks and selective breeding, has increased the number of deleterious genetic variants in dogs. This is evident in the higher genetic load observed in domestic dogs compared to gray wolves, which is attributed to less efficient natural selection during domestication and breed formation (Marsden et al., 2015). Furthermore, studies on Toll-like receptors (TLRs) have shown that domestic dogs possess protective alleles against inflammatory bowel disease (IBD) that are absent in wild canids like the maned wolf and red wolf, suggesting that these protective alleles developed post-domestication (Henson et al., 2017). 3.3 Overview of disease profiles in wolves vs dogs The disease profiles of wild wolves and domestic dogs differ significantly due to genetic and environmental factors. Domestic dogs have been found to carry a higher burden of deleterious genetic variants, which can lead to a variety of breed-specific diseases (Marsden et al., 2015). For example, African indigenous dogs have developed genetic adaptations to tropical parasites, including genes linked to immunity and resistance to severe malaria, which are not present in wild wolves (Liu et al., 2018). In contrast, wild wolves, such as those in Yellowstone National Park, show a relationship between reduced genomic variation and increased severity of diseases like sarcoptic mange, highlighting the importance of genetic diversity in disease resistance (DeCandia et al., 2020). Additionally, the lack of protective alleles against IBD in wild canids further underscores the differences in disease susceptibility between wild and domestic canids (Henson et al., 2017). The comparative analysis of wild wolves and domestic dogs reveals significant genetic divergence due to domestication, impacting immune gene diversity and disease profiles. Structural and copy number variations have played a crucial role in this divergence, with domestic dogs showing higher genetic loads and specific adaptations to their environments. The differences in disease susceptibility and genetic diversity between wild and domestic canids highlight the complex interplay between genetics and domestication in shaping the health and evolution of these species. 4 Immune System Differences in Canids 4.1 Innate immunity: genetic and molecular insights Innate immunity, the first line of defense against pathogens, shows significant genetic variation between wild wolves and domestic dogs. Studies have identified several genes related to the innate immune response that are differentially expressed between these canids. For instance, genes such as CCL23, TRIM10, DUSP10, RAB27A, CLEC5A, and GCH1 are more highly expressed in wolves, suggesting a stronger innate immune response compared to dogs (Yang et al., 2018). Additionally, Toll-like receptors (TLRs), which play a crucial role in pathogen recognition, exhibit notable polymorphisms in wild canids. For example, the TLR5 gene in red wolves and maned wolves shows novel polymorphic positions not found in domestic dogs, indicating potential differences in disease susceptibility and immune response (Henson et al., 2017). These genetic variations highlight the evolutionary adaptations in the innate immune system of wild canids, possibly due to their exposure to a broader range of pathogens in the wild. 4.2 Adaptive immunity: diversity in t-cell receptor and mhc complexes The adaptive immune system, particularly the diversity in T-cell receptors (TCRs) and major histocompatibility complex (MHC) genes, also differs significantly between wild wolves and domestic dogs. MHC genes, which are critical for antigen presentation and immune response, show varying levels of polymorphism. In wild canids, such as the European roe deer, high levels of amino acid diversity in MHC genes have been observed, suggesting a robust adaptive immune response to diverse pathogens (Quéméré et al., 2015). In contrast, domestic dogs have undergone genetic bottlenecks and selective breeding, leading to reduced MHC diversity and potentially higher susceptibility to certain diseases (Marsden et al., 2015). This reduced genetic diversity in domestic dogs' MHC complexes may compromise their ability to respond to new or evolving pathogens effectively.
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