Characterisation of the green turtle’s leukocyte subpopulations by flow cytometry and evaluation of their phagocytic activity

Abstract

Phagocytosis is a fundamental aspect of innate immunity that is conserved across many species making it a potentially useful health-assessment tool for wildlife. In non-mammalian vertebrates, heterophils, monocytes, macrophages, melanomacrophages, and thrombocytes all have phagocytic properties. Recently, B lymphocytes from fish, amphibians, and aquatic turtles have also showed phagocytic capacity. Phagocytes can be studied by flow cytometry; however, the use of this tool is complicated in reptiles partly because nucleated erythrocytes complicate the procedure. We separated green turtle leukocytes by density gradient centrifugation and identified subpopulations by flow cytometry and confocal microscopy. Additionally, we assessed their ability to phagocytize Fluorspheres and Ovoalbumin-Alexa. We found that heterophils and lymphocytes but not monocytes could be easily identified by flow cytometry. While heterophils from adults and juvenile turtles were equally able to phagocytize fluorspheres, adults had significantly more phagocytic ability for OVA-Alexa. Lymphocytes had a mild phagocytic activity with fluorospheres (27-38 %; 39-45 %) and OVA-Alexa (35-46 %; 14-22 %) in juvenile and adult green turtles, respectively. Confocal microscopy confirmed phagocytosis of fluorospheres in both heterophils and lymphocytes. This provides the first evidence that green turtle lymphocytes have phagocytic activity and that this assay could potentially be useful to measure one aspect of innate immunity in this species.

Effects of trophic exposure to diclofenac and dexamethasone on hematological parameters and immune response in freshwater fish

“…Importantly, along with these changes, compensatory responses are taking place, thus leading to the observed results. The environmental change shows a great sensitivity with regard to these parameters [31]. In the analyses of white blood cells, a decrease was observed in fish exposed to diclofenac or dexamethasone.…”

“…The polymorphonuclear cells are the most important leukocytes in fish. The environmental change shows a great sensitivity with regard to these parameters [31]. The lymphocytes are the main defense mechanism in the adaptive immune response in fish; therefore, a decrease in the number of mononuclear leukocytes represents a decrease in one immune response, ultimately predisposing fish to diseases [32].…”

Host stress physiology and Trypanosoma haemoparasite infection influence innate immunity in the woylie ( Bettongia penicillata )

“…Deviations from normal phagocytic function such as that which might occur with stress [21] can render animals more susceptible to disease [22].…”

“…Phagocytosis flow cytometry is a high throughput, quantitative assay, which assesses leukocytes' capacity to phagocytose fluorescently labelled bacteria [25,27]. It has numerous advantages for use in comparative immunology and has proven to be a rapid, reliable tool to evaluate phagocytosis in different species ranging from teleosts [28], mice and macaques [27] to salamanders [29], seals [30], camels [31], sea turtles [22,32], beluga whales [33] and Tasmanian devils [34]. The ex vivo nature of the phagocytosis flow cytometry assay also has advantages over in vivo immunologic tests such as allograft rejection, which may be ethically challenging to carry out in critically endangered species.…”

Out of the Shell: Exploring The Phagocytic Capabilities of the B Cell and Isolated Lymphoid Follicle-lie Structures in the Red-Eared Slider, Trachemys Scripta

“…Within the last decade, however, there have been several studies in T. scripta that have given insight into both their adaptive and innate immunity . It has been reported that turtles, including T. scripta, contain populations of B cells with phagocytic potential, not unlike that of the B-1 cell in mammals (Muñoz, Franco-Noguez, Gonzalez-Ballesteros, Negrete-Philippe, & Flores-Romo, 2014;. Given that turtles appear to share some, but not all, immune functions in common with other vertebrates, they provide an interesting group for further study.…”