The amphibian immune system

Abstract

Amphibians are at the forefront of bridging the evolutionary gap between mammals and more ancient, jawed vertebrates. Currently, several diseases have targeted amphibians and understanding their immune system has importance beyond their use as a research model. The immune system of the African clawed frog, Xenopus laevis , and that of mammals is well conserved. We know that several features of the adaptive and innate immune system are very similar for both, including the existence of B cells, T cells and innate-like T cells. In particular, the study of the immune system at early stages of development is benefitted by studying X. laevis tadpoles. The tadpoles mainly rely on innate immune mechanisms including pre-set or innate-like T cells until after metamorphosis. In this review we lay out what is known about the innate and adaptive immune system of X. laevis including the lymphoid organs as well as how other amphibian immune systems are similar or different. Furthermore, we will describe how the amphibian immune system responds to some viral, bacterial and fungal insults. This article is part of the theme issue ‘Amphibian immunity: stress, disease and ecoimmunology’.

Introduction to the special issue Amphibian immunity: stress, disease and ecoimmunology

“…Although many aspects of the amphibian immune system have been described in the last decades, most studies have been dedicated to the Xenopus genus [ 34 ]. In this issue, [ 35 ] describes the current knowledge about the amphibian immune system more widely. The authors describe molecular and cellular characteristics, tissue composition and function in anurans, urodeles and legless caecilians [ 35 ].…”

“…In this issue, [ 35 ] describes the current knowledge about the amphibian immune system more widely. The authors describe molecular and cellular characteristics, tissue composition and function in anurans, urodeles and legless caecilians [ 35 ]. In addition, they point to several immune aspects related to innate and adaptive responses in amphibians, which are better characterized in Xenopus , axolotl and the giant salamander.…”

The complement system and its involvement in inhibition of Batrachochytriym dendrobatidis, a lethal fungal pathogen of amphibians

“…Amphibians have gained prominence as valuable model species in ecoimmunology for at least three important reasons. First, although many components of the amphibian immune system are highly conserved among vertebrates, the diversity of immunological responses among amphibian host species provides insights into susceptibility to disease and the generation of resistance mechanisms (Assis et al, 2022;Ruiz & Robert, 2023). Second, as ectotherms, environmental conditions (e.g., temperature, relative humidity, and rainfall) that affect amphibian physiology also mediate immunity and the manifestation of disease (Raffel et al, 2006;Rollins-Smith et al, 2011;Rollins-Smith, 2017;Le Sage et al, 2021;Rosa et al, 2022).…”

“…Overall, amphibians have shed light on host immune responses, disease dynamics, and the interactions of environmental variables and immunity for a wide variety of organisms (Assis et al, 2022). As such, a better understanding of amphibian immunity can make meaningful contributions to the field of ecoimmunology, disease ecology, and the study of infectious disease in general (Assis et al, 2022;Ruiz & Robert, 2023).…”

Amphibian Hymenochirus boettgeri as an experimental model for infection studies with the chytrid fungus Batrachochytrium dendrobatidis

“…Originally inhabiting pools, rivers, and stagnant waters in forested regions of subequatorial Africa, H. boettgeri can be readily purchased from the aquarium trade, allowing laboratories worldwide to use it. In addition, H. boettgeri is a promising species for use as a model organism in the Bd-amphibian system as it: i) is susceptible to Bd [ 12–14 ]; ii) tolerates high temperatures that eliminate Bd infection ([ 12 , 15 ]; also supported by our data); iii) reproduces throughout the year and completes metamorphosis in approximately 5 weeks [ 16 , 17 ]; iv) is small and fully aquatic, which simplifies husbandry and environmental manipulation; v) has a complete genome sequence [ 18 ] and belongs to the same family as X. laevis [ 19 ], which means that tools that work on X. laevis may be applied here; and vi) has a characterized antimicrobial peptide repertoire [ 20 ], and general inferences about the functioning of its immune system can be made based on the extensively characterized immune system of the closely related species, X. laevis [ 21 ].…”