Amphibian mast cells: barriers to deadly chytrid fungus infections

Abstract

AbstractGlobal amphibian declines are largely driven by deadly disease outbreaks caused by the chytrid fungus,Batrachochytrium dendrobatidis(Bd). In the time since these disease outbreaks were first discovered, much has been learned about the roles of amphibian skin-produced antimicrobial components and skin microbiomes in controllingBd. Yet almost nothing is known about the roles of skin-resident immune cells in anti-Bddefenses. Notably, mammalian mast cells reside within and serve as key immune sentinels in barrier tissues like the skin. Thus, they are critical to immune recognition of pathogens and to orchestrating the ensuing immune responses. Accordingly, we investigated the roles ofXenopus laevisfrog mast cells duringBdinfections. Our findings indicate that enrichment ofX. laevisskin mast cells confers significant anti-Bdprotection and ameliorates the inflammation-associated skin damage caused byBdinfection. Moreover, enrichingX. laevismast cells promotes greater mucin content within cutaneous mucus glands and protects frogs fromBd-mediated changes to their skin microbiomes. Together, this work underlines the importance of amphibian skin-resident immune cells in anti-Bddefenses and introduces a novel approach for investigating amphibian host-chytrid pathogen interactions.