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The immune responses of the Tasmanian devil (Sarcophilus harrisii) and the devil facial tumour disease

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Kreiss, A (2009) The immune responses of the Tasmanian devil (Sarcophilus harrisii) and the devil facial tumour disease. PhD thesis, University of Tasmania.

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Abstract

The Tasmanian devil (Sarcophilus harrisii) is a carnivorous marsupial endemic to the
island-state of Tasmania, Australia and is currently under threat from a devastating
disease named Devil Facial Tumour Disease (DFTD). This disease has been identified
as a tumour, which starts in, or around, the mouth, face or neck and invariably causes
the death of the affected animal within a few months after the first signs of disease.
Recent cytogenetic and molecular research led to the proposal that the tumour is
transmitted as an allograft after cellular inoculation (probably by biting) from an
infected to a healthy animal. The transmissibility of this tumour by cell implantation
raises many questions about the status of immune responses of Tasmanian devils and
the MHC diversity of the species.
Several aspects of the immune response of the Tasmanian devil were investigated to
determine whether a lack of immune competence may account for the ability of DFTD
to be established in recipient devils. Using histology and immunohistochemistry
techniques, the immune tissues of healthy and diseased devils were described and
provided evidence that the species has the necessary structural components for immune
responses. However, DFTD tumours were also analysed using histology and
immunohistochemistry and there appeared to be a lack of immune cell infiltration in the
tumour grafts, suggesting that DFTD develops unrecognised by the immune system.
To test the functional competency of cellular and humoral immune responses, a series
of in vitro and in vivo assays was undertaken. Neutrophils and lymphocytes isolated
from healthy and DFTD-affected Tasmanian devils utilised in in vitro neutrophil
phagocytosis and lymphocyte mitogen stimulation showed competent cellular function.
In vivo immunisation of Tasmanian devils with horse red blood cells resulted in
prominent humoral immune responses. These results provided support for the concept
that the species is not severely immunosuppressed and transmission of DFTD is not a
consequence of an impaired immune response.
Analyses of the allo-reactivity of the devil population were performed through in vitro
mixed lymphocyte reactions and in vivo skin grafts between unrelated devils. Results
from these experiments demonstrated that most devils had functional allo-recognition.
Importantly, skin grafts between unrelated devils were immunologically rejected,
indicating that spreading of DFTD is not simply due to a lack of MHC diversity in this
species.
To investigate whether immunity against DFTD could be induced, six Tasmanian devils
were immunised with inactivated DFTD tumour cells. Most of these animals exhibited a
very weak immune response against DFTD. Three of these devils were challenged with
live DFTD tumour cells and succumbed to the disease. However, one devil had a more
prominent antibody response against DFTD and was protected against a first challenge,
suggesting that immunity was protective, but likely to be short-term.
A survey for natural immune recognition of DFTD tumour cells in the devil population
found one devil with antibodies against DFTD, and this animal was found a year later
with no signs of the disease. This provided an insight that some individual devils might
recognise and reject the tumour allograft.

Item Type: Thesis (PhD)
Copyright Holders: The Author
Copyright Information:

Copyright 2009 the Author

Date Deposited: 30 Mar 2015 05:22
Last Modified: 11 Mar 2016 05:53
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