Extracellular trap-like fiber release may not be a prominent defence response in snails: evidence from three species of freshwater gastropod molluscs

Abstract

The discovery that mammalian neutrophils generate extracellular chromatin fibers that entrap/kill bacteria supported a new paradigm for innate immunity in animals. Similar findings in other models across diverse taxa have led to the hypothesis that the phenomenon is ancient and evolutionary conserved. Here, using a variety of synthetic (e.g. peptidoglycan) and biological (e.g. trematode larvae) components to investigate extracellular trap-like (ET-like) fiber production in vitro by haemocytes of Lymnaea stagnalis, Radix lagotis and Planorbarius corneus snails, ET-like fibers were rarely observed. We suggest, therefore, that ET-like fibers play a marginal role in defence of these snail species and thus the fiber production may not be a critical process underpinning immunity in all invertebrate species.

Hemocyte extracellular traps of Manila clam Ruditapes philippinarum: Production characteristics and antibacterial effects

“…However, there is no research on the formation of ETs in R. philippinarum. And knowledge of the functions of ETs is still limited in mollusks, mainly restricted to their antibacterial activity (Poirier et al, 2014;Ng et al, 2015;Skala et al, 2018). In the present study, the formation of ETs was first identified in the clam R. philippinarum, and also the potential mechanism of ET formation was also investigated.…”

“…For example, the proteobacteria Escherichia coli could induce the ET formation of shrimp hemocytes, and the produced DNA fibers participated in the ET-mediated bactericidal killing (Ng et al, 2015). In snails, ET-like fibers could be induced by a variety of synthetic (e.g., peptidoglycan) and biological (e.g., trematode larvae) components (Skala et al, 2018). However, knowledge on the function of ETs is still limited in the marine mollusks so far.…”

Mitochondria are essential for antibacterial extracellular trap formation mediated by zymosan in hemocytes of Ruditapes philippinarum

“…Various types of vertebrate cells such as neutrophils, mast cells, eosinophils and macrophages, have been reported to possess the ability to generate ETs (Chow et al, 2010;von Köckritz-Blickwede et al, 2008;Yousefi et al, 2008). Among invertebrates, ETs have been found in shrimp, oysters, mussels, earthworms, snails and amoebae (Homa et al, 2016;Ng et al, 2013;Poirier et al, 2014;Robb et al, 2014;Skála et al, 2018;Zhang et al, 2016). However, knowledge on the formation and antibacterial activities of hemocyte ETs is still deficient in invertebrates.…”

Snail defence responses to parasite infection: The Lymnaea stagnalis-Trichobilharzia szidati model

“…2B-E, 3C-D) (Dikkeboom et al, 1987;Adema et al, 1993). Additionally, haemocytes of L. stagnalis (and those of Planorbarius corneus and Radix lagotis snails) have recently been shown to generate extracellular trap-like (ET-like) fibers in vitro (Skála et al, 2018). Despite the fact that the functional characterisation of the fibers in the snail defence is required, these structures produced by, for example, neutrophils (neutrophil extracellular traps) of vertebrates or haemocytes (ET-like fibers) of invertebrates including molluscs are considered to facilitate elimination of bacteria and eukaryotic unicellular/multicellular parasites in the extracellular milieu (Hermosilla et al, 2014;Robb et al, 2014;Poirier et al, 2014;Lange et al, 2017).…”