Robert, J. & Ohta, Y. Comparative and developmental study of the immune system in Xenopus. Dev. Dyn. 238, 1249-1270

Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York, USA.
Developmental Dynamics (Impact Factor: 2.38). 06/2009; 238(6):1249-70. DOI: 10.1002/dvdy.21891
Source: PubMed


Xenopus laevis is the model of choice for evolutionary, comparative, and developmental studies of immunity, and invaluable research tools including MHC-defined clones, inbred strains, cell lines, and monoclonal antibodies are available for these studies. Recent efforts to use Silurana (Xenopus) tropicalis for genetic analyses have led to the sequencing of the whole genome. Ongoing genome mapping and mutagenesis studies will provide a new dimension to the study of immunity. Here we review what is known about the immune system of X. laevis integrated with available genomic information from S. tropicalis. This review provides compelling evidence for the high degree of similarity and evolutionary conservation between Xenopus and mammalian immune systems. We propose to build a powerful and innovative comparative biomedical model based on modern genetic technologies that takes take advantage of X. laevis and S. tropicalis, as well as the whole Xenopus genus. Developmental Dynamics 238:1249-1270, 2009. (c) 2009 Wiley-Liss, Inc.

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    • "Although metamorphosis is generally rudimentary, or even cryptic in urodelian species (e.g. salamanders, newts), in anuran species it is a major developmental transition between two distinct immune systems [reviewed in (Flajnik et al., 1987; Robert and Ohta, 2009)]. In addition, the different ecological niches occupied by tadpole and adult stages are presumably populated by different pathogens, thus representing unique immunological pressures. "
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    ABSTRACT: Macrophage lineage cells represent the cornerstone of vertebrate physiology and immune defenses. In turn, comparative studies using non-mammalian animal models have revealed that evolutionarily distinct species have adopted diverse molecular and physiological strategies for controlling macrophage development and functions. Notably, amphibian species present a rich array of physiological and environmental adaptations, not to mention the peculiarity of metamorphosis from larval to adult stages of development, involving drastic transformation and differentiation of multiple new tissues. Thus it is not surprising that different amphibian species and their respective tadpole and adult stages have adopted unique hematopoietic strategies. Accordingly and in order to establish a more comprehensive view of these processes, here we review the hematopoietic and monopoietic strategies observed across amphibians, describe the present understanding of the molecular mechanisms driving amphibian, an in particular Xenopus laevis macrophage development and functional polarization, and discuss the roles of macrophage-lineage cells during ranavirus infections.
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    • "This reduction in infection rate may result from the interplay between virus load, which depends on the exposure/re-exposure scenario, and the development of the tadpole immune system over time. Over the course of the larval development, the potential immune response increases in strength, complexity and diversity as the initial innate components are gradually supplemented by the adaptive components of immunity (Robert & Ohta, 2009). In Xenopus, for example, the larvae gradually develop spleen B cells, Lymphopoiesis, lymphocytes and immunoglobulin from Gosner stages 20 to 35 with the maximal immunity reached around Gosner stages 34–35. "
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    ABSTRACT: Transmission is a central feature of pathogen fitness and influences host population dynamics. The form and magnitude of transmission rates determine whether a pathogen establishes itself in a host population and the proportion of a population that becomes infected. While the effects of environmental variation on pathogen transmission dynamics have received substantial attention, the time and number of pathogen exposure in relation to host ontogeny has been relatively less investigated. Such understanding is particularly important in host species exhibiting distinct life-history stages such as amphibians as this temporal variation in infection modulates transmission trends at the population level. We investigated the role of the timing and number of ranavirus (FV3) exposures on infection rate and mortality patterns in Lithobates pipiens tadpoles in a two-step laboratory experiment with four treatments: individuals exposed as hatchlings but not as tadpoles, individuals not exposed as hatchlings but exposed as tadpoles, individuals exposed both as hatchlings and tadpoles and individuals that were never exposed. Our results indicate that individuals exposed twice presented higher infection and mortality rates over individuals exposed only once (infection: 40 vs. 16%; mortality: 16.8 vs. 8.1%, respectively). Among individuals exposed only once, but at different time, no difference in mortality was observed; yet, dissimilar infection rates indicate a differential capacity to carry and transmit virions among various developmental stages suggesting distinct epidemiological roles. Our results stress the importance of considering stage-dependent host susceptibility to better understand infection patterns and transmission dynamics and advocate its incorporation in models and field study designs.
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    • "Xenopus has been and still is one of the top model systems for the study of fundamental questions related to development, immunology, toxicology, neurobiology, embryology and regenerative biology (Du Pasquier et al., 1989; Khokha, 2012; Robert and Ohta, 2009). More recently Xenopus has also been increasingly used as a model for understanding tumor biology, transplantation biology, self tolerance and autoimmunity [reviewed in (Edholm and Robert, 2013). "
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    ABSTRACT: Tumors have the ability to grow as a self-sustaining entity within the body. This autonomy is in part accomplished by the tumor cells ability to induce the formation of new blood vessels (angiogenesis) and by controlling cell trafficking inside the tumor mass. These abilities greatly reduce the efficacy of many cancer therapies and pose challenges for the development of more effective cancer treatments. Hence, there is a need for animal models suitable for direct microscopy observation of blood vessel formation and cell trafficking, especially during early stages of tumor establishment. Here, we have developed a reliable and cost effective tumor model system in tadpoles of the amphibian Xenopus laevis. Tadpoles are ideally suited for direct microscopy observation because of their small size and transparency. Using the thymic lymphoid tumor line 15/0 derived from, and transplantable into, the X. laevis/gilli isogenic clone LG-15, we have adapted a system that consists in transplanting 15/0 tumor cells embedded into rat collagen under the dorsal skin of LG-15 tadpole recipients. This system recapitulates many facets of mammalian tumorigenesis and permits real time visualization of the active formation of the tumor microenvironment induced by 15/0 tumor cells including neovascularization, collagen rearrangements as well as infiltration of immune cells and melanophores.
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