REGULAR readers of this blog will know that I am a big fan of the Tasmanian Devil. It is a black and white ball of fur, underneath which is a marsupial carnivore, one so keen on its food that once it starts eating nothing can distract it, and nothing will be left once it is finished (its blood-curdling squeals of delight are the origin of its name 'devil', when heard by early settlers at night). It is also dying.
This from a previous post of mine:
In a phenomenon almost unique to science, the already small population is suffering from a transmissible form of cancer called Devil Facial Tumour Disease (DFTD), with over 70% of the population infected. It is almost completely lethal, causing swelling in the mouth and face, leading to suffocation and starvation. 80% of the population has been wiped out since its discovery in 1996, and it is predicted that the species could be extinct within 25-35 years.I have previously covered the discovery that the low genetic diversity in the species has existed in the population for at least 100 years and how this has implications on how we decide which species to invest conservation efforts on. I also introduced the disease and explained why low genetic diversity in the species could be a blessing or disaster for its survival, and how, biologically speaking, the cancer is utterly remarkable — it is contagious and makes its own myelin, a protein usually seen only in the nervous system, which the immune system never attacks.
I hurry through these details because there is new news. It is covered very nicely here and here by Ed Yong, but I shall cut to the chase:
It was assumed that Devils are vulnerable to DFTD because they have such low genetic diversity that their immune systems cannot identify the tumour as foreign (or non-self), but this wasn't true, because skin grafts between individuals were rejected. Instead, it turns out that there is no immune reaction because the tumour is completely invisible to the immune system — key molecules expressed on every cell that indicate cell and animal identity are completely missing. Importantly, the researchers (Siddle et al.) have found a way to trick the tumours into expressing these markers, thereby exposing them to the immune system, ready and waiting. Head over to Ed's articles to find out how or read the source paper here.
Siddle, H. et al. Reversible epigenetic down-regulation of MHC molecules by devil facial tumour disease illustrates immune escape by a contagious cancer. PNAS 11 March 2013 doi:10.1073/pnas.1219920110