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Comparative Immunology
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Anuran amphibians can have two or three distinct immunoglobulin classes. They have an IgM that consists of either pentamers or hexamers (in Xenopus) and one or two low molecular weight molecules. They have an IgY with a 66 kDa θ heavy chain and/or a IgX with a 64 kDa χ heavy chain. Xenopus immunoglobulins also contain two types of light chain perhaps equivalent to mammalian κ and λ chains. Anuran amphibians possess secretory immunoglobulins in bile and the intestine (but not in skin mucus). These consist of IgM and IgY but not IgA. In the axolotl (Ambystoma mexicanum) IgY is a secretory immunoglobulin found in close association with secretory component-like molecules. This is different from what occurs in Xenopus where IgY behaves like avian IgY or mammalian IgG. Amphibian antibody diversity is generated in a fashion similar to that of mammals.
Tumors of the Nasal Cavity in Nondomesticated Animals
Published in Gerd Reznik, Sherman F. Stinson, Nasal Tumors in Animals and Man, 2017
Richard J. Montau, Marion G. Valerio, John C. Harshbarger
In amphibians, spontaneous olfactory neuroepitheliomas were discovered several years apart in two related adult axolotls, Ambystoma mexicanum, from the same colony of 400 individuals.21–23 The better of the two tumors studied had enlarged and modified the olfactory chambers, had grown through the palate into the buccal cavity, and had replaced all tissues in the lower jaw in its route to its anterior terminus. It had not grown significantly into dorsal or lateral nonolfactory tissues of the upper jaw. The tumor was successfully homografted to flank musculature, but second-set transplants regressed at varying times after initial growth. The homograft grew to a large size but was less well-vascularized and less invasive than the primary. Both primary and homograft were organoid tumors consisting of well-differentiated neuroepithelium often arranged in olfactory tubes represented as multilayered rosettes. Lumens were definitely shown to contain cilia. Mitotic activity varied greatly from one area of the tumor to another, but averaged 25/1000 tumor cells vs. 2/1000 normal surface epithelial cells and connective tissue stroma cells. Tumor cell karyotypes were aneuploid, ranging from 12 to 36 chromosomes in typical metaphases and up to 84 chromosomes in atypical metaphases compared to the normal 28.
Evolutionary Underpinnings of Innate-Like T Cell Interactions with Cancer
Published in Immunological Investigations, 2019
Maureen Banach, Jacques Robert
The phylogeny of class I-like MHC is less defined due to the rapid and dynamic evolutionary rates of these genes (Adams and Luoma, 2013). As such, MHC class I-like genes among closely related species often exhibit species-specific attributes, differing in gene composition, number or synteny (Adams and Luoma, 2013). True orthologs of CD1d are found in mammals, birds, and reptiles; however, they have not been found in the genomes of fish or amphibians (Brossay et al., 1998; Dascher, 2007; Miller et al., 2005; Rogers and Kaufman, 2016; Salomonsen et al., 2005; Yang et al., 2015). Furthermore, a detailed characterization of syntenic regions between X. tropicalis and X. laevis did not reveal any CD1d-like sequences or CD1 locus (Drs Yuko Otha and Martin Flajnik, personal communication). Instead, the genomes of cartilaginous and bony fish as well as amphibians harbor expanded families of MHC class I-like genes (Edholm et al., 2016). For instance, the genome of Atlantic cod possesses an unusually high number of MHC class I loci, probably to compensate the absence of the MHC class II components (Star et al., 2011). Similarly, the genome of the urodele amphibian Ambystoma mexicanum is featured by a high number of MHC class I-like genes; however, the functions of these genes are still unclear (Sammut et al., 1999). Among other amphibians, Xenopus laevis has also a diversified family of 23 MHC class I-like genes, termed XNC. These genes are genetically unlinked from the MHC class I locus and clustered in the telomeric region of chromosome 8L and 8S (Banach et al., 2017; Flajnik et al., 1993). Hypothetically, due to similar evolutionary pressures, molecules of different nucleotide sequences but with a similar overall structure may be selected to carry out the same function via convergent molecular evolution (Doolittle, 1994). Indeed, within the XNC genes, XNC10 has been identified and characterized as a functional analog of CD1d (Edholm et al., 2013). Akin to the role of CD1d in NKT cell biology, XNC10 is required for the development and function of NKT analogs, termed iT cells (Edholm et al., 2013, 2015). Although X. laevis is currently the only species outside mammals with confirmed functional iT cell subsets, other amphibians and fish with extended MHC class I-like genes may likely have iT cell subsets.