Immunohistochemical Characterization of Langerhans Cells in the Skin of Three Amphibian Species

Simple Summary Amphibians are classified into three orders with different morphological characteristics: Anura, Apoda, and Caudata. In this article, the importance of skin for amphibians is discussed as it represents a physical, chemical, immunological, and microbiological barrier to pathogen insult is discussed. Langerhans cells (LCs) are antigen-presenting cells constituting an important component of the immune system in the skin. This study aims to characterize Langerhans cells in the skin of Lithobates catesbeianus (Shaw, 1802), Amphiuma means (Garden, 1821), and Typhlonectes natans (Fischer, 1880) with several antibodies previously used to mark the same cells in other vertebrates. The results showed that the distribution of LCs is very similar in the three amphibian species examined, despite their different habitats. In conclusion, the amphibian dendritic cells are morphologically and immunohistochemically homologous to the LCs of all vertebrates so they can be considered as starting points to better understand the phylogeny of the vertebrate immune system.Abstract The amphibian taxon includes three orders that present different morphological characteristics: Anura, Caudata, and Apoda. Their skin has a crucial role: it acts as an immune organ constituting a physical, chemical, immunological, and microbiological barrier to pathogen insult and conducts essential physiological processes. Amphibians have developed specialized features to protect the vulnerable skin barrier, including a glandular network beneath the skin surface that can produce antimicrobial and toxic substances, thus contributing to the defense against pathogens and predators. This study aims to characterize Langerhans cells in the skin of Lithobates catesbeianus (order: Anura; Shaw, 1802), Amphiuma means (order: Caudata; Garden, 1821), and Typhlonectes natans (order: Apoda; Fischer, 1880) with the following antibodies: Langerin/CD207 (c-type lectin), Major Histocompatibility Complex (MHC)II, and Toll-like receptor (TLR)2 (expressed by different types of DCs). Our results showed Langerhans cells positive for Langerin CD/207 in the epidermis of the three species; moreover, some antigen-presenting cells (APCs) in the connective tissue expressed TLR2 and MHCII. The distribution of the Langerhans cells is very similar in the three amphibians examined, despite their different habitats. A greater knowledge of the amphibian immune system could be useful to better understand the phylogeny of vertebrates and to safeguard amphibians from population declines. Furthermore, the similarities between amphibians' and human skin concerning immunological features may be useful in both biology and translational medicine.