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Thanks Graham, I have been looking at several articles, when i get done with the pig roast this weekend, Ill send you some links (remind me Monday)
 

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Maybe if we can stop depleting the ozone, we could prevent the high temps hitting our oceans, and prevent some of the bleaching going on and thereby prevent disease and death of our corals! (That would help at least get rid of one stressor!) Great read...the idea of someday knowing how to prevent sickness, disease , death in our corals, wow-what beauty our oceans could house.
 

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Discussion Starter · #7 ·
I was kind of surprised that there's evidence of cell-mediated immunity in animals as simple as corals. But I suppose there would have to be, else viruses would have taken their toll on them long ago.

But you're right Viv, who knows how well corals could ward off the various (apparently) pathologic bacterial epidemics they succumb to if they weren't already under some stress. I do have to wonder if these "epidemics" (black/white band disease, etc) are any more prevalent in current times or if we're just noticing them more. It's kind of the Catch-22 of Western medicine - is the disease more prominent or are you just better at diagnosing/finding it?
 

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That's a remarkable publication, thanks for posting it!

FWIW, cell-mediated immunity in invertebrates generally refers to phagocytosis or encapsulation of microorganisms. There is little evidence that hemocytes (blood cells) function against viral infection (although a possible mechanism was proposed by Zambon et al (Proc Natl Acad Sci U S A. 2005 May 17; 102(20): 7257–7262.) Many researchers consider RNA interference a primary defensive mechanism that protects invertebrates from viral infection.

JM
 

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Discussion Starter · #9 ·
JoshMatt said:
FWIW, cell-mediated immunity in invertebrates generally refers to phagocytosis or encapsulation of microorganisms. There is little evidence that hemocytes (blood cells) function against viral infection (although a possible mechanism was proposed by Zambon et al (Proc Natl Acad Sci U S A. 2005 May 17; 102(20): 7257–7262.)
Not sure if you saw it, but there was a section in the paper about histological graft rejection. They found (in one species of gorgonian) autografts were widely accepted while allografts were rejected and caused severe necrosis. So grafts from the same individual survived, but grafts from a different individual of the same species did not. In addition, there was memory, as subsequent allografts were rejected in a much shorter time than the initial one.

While it's a huge leap (and no doubt wrong) to assume the same mechanism exists in corals as in humans, human graft rejection is essentially mediated entirely by leukocytes (along with the associated APC's, cytokines, etc). It would be fascinating to know this "other way" of doing it. There is definitely some cytotoxic cascade occurring. It could also be nothing more than what we see when two corals come in contact with each other, but gorgonians aren't notorious stingers, so I think "nematocystic" response is not the factor. Maybe it's something more akin to complement activity...?


Many researchers consider RNA interference a primary defensive mechanism that protects invertebrates from viral infection.
Can you point me to any info on this? I'd love to read about it. :)
 

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I haven't read the part about the graft rejection, but similar behaviors have been noted in insects. There is a lot of old research where investigators would take implants from one insect and put it into another and see what became of it. As far as I can tell, hemocytes are likely to be a major factor in destruction of these grafts. Non-self recognition of eukaryotic tissues is poorly understood in invertebrates (I think many of the factors have been resolved for most prokaryotes, and are very similar to the pattern recognition receptors used by vertebrates). Interestingly, a number of parasitic wasps whose larvae feed inside catepillars (while it is still alive), protect their larvae by injecting a virus that kills the host's hemocytes.

Immunological memory is pretty speculative in inverts, although there was a report that suggested the cockroaches were able to "remember" pathogenic microbes. It seems to me there was a paper in Science a couple of years ago looking at copepods, too, but I can't remember the details. Regardless, no one else has found evidence for memory. Immunocompentent invert hemocytes are more like neutrophils or macrophages than lymphocytes, and in the case of corals, I would suspect there was some persistent activating factor (either from the host, or from the previous implant) that kept the hemocytes in an activated state and they responded more rapidly to the second challenge. But that's just a wild guess on my part without any real evidence.

As far as RNAi in viral defense, here's a recent one for Drosophila: RNA interference directs innate immunity against viruses in adult Drosophila.
Science. 2006 Apr 21;312(5772):452-4. Epub 2006 Mar 23.

JM
 
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