Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!boulder!pell
From: pell@boulder.Colorado.EDU (Anthony Pelletier)
Newsgroups: sci.bio
Subject: Re: Who Has Immunity?
Message-ID: <7930@boulder.Colorado.EDU>
Date: 5 Apr 89 15:46:05 GMT
References: <2600@tank.uchicago.edu> <7914@boulder.Colorado.EDU>
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Reply-To: pell@boulder.Colorado.EDU (Anthony Pelletier)
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Organization: University of Colorado, Boulder
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(Brian W. Ogilvie) writes:
>>How far down in the animal kingdom is some type of immune system
>>found? Do, say, mollusks have immune systems? What about annelids?
>
(Sean Eddy) writes:
>Specific antibody responses seem to be limited to vertebrates.
>
>I have heard rumors that some invertebrates may make small 
>antibacterial peptide antibiotics, of broad specificity.
>I dimly recall hearing something similar about plants.
>
>- Sean Eddy
>- eddy@boulder.colorado.EDU		!{hao,nbires}!boulder!eddy	

Actually, Sean, plants have a rather effective way of dealing with pathogens,
seeing as they are notably inefficient at running away.  you could have
asked...not that I am bothered by your "dim rumors." (+:  just kidding buddy)

None of the methods are exactly like an "immune system," per sey, so I won't
go into too much detail.  But one rather cute one worked at this universtiy
a while back was the "hypersensitive response."  It seems that there are
ani-fungal and anti-bacterial polysacharides in the cell wall of plants, as
well as things cyto-toxic to the plant cell *itself*.  In the process of trying
to chew its way into the cell, the pathogen releases these agents from the
cell wall and is those the agent of its own distruction.  The plant cells
surrounding the invasion also die, to remove available hosts for surviving
pathogens.  As an aside, those more succesful pathogens usually get in by
secreating auxin and cytokinin-like peptides and thereby induce an ingrowth
in the cell wall (the "infection thread" or "infection tube").  So they
don't actually destroy any plant tissue until they are inside (symbionts
such as rhizobia use this method too).

-tony