The real role of the immune system

Ken Frauwirth BioKen frauwirt at notmendel.Berkeley.EDU
Wed May 10 15:47:23 EST 1995

In article <3oqkcs$noc at>,  <Chris Thoburn> wrote:
>I must admit that when I posted my question reguarding the real role of the 
>immune system last week I was not exactly certain of the response it would draw.
>Today looking at the replies I find myself simply amazed.  I have before me a 
>highly detailed and structured response from Polly Matzinger at NIH.   

>In reply to this post, Psycler(TKendric) of NETCOM reposts my original message 
>but rather than trying to answer it, attacks the post from PM.  Furthermore, in 
>other 'tangent'
>posts, Ephraim Fuchs and Ken Frauwirth begin to 'discuss' theories (which BTW 
>was my original intent) but focus around the big post of PM.

Actually, my posts, and Ephraim Fuchs followups, were direct responses to 
Polly Matzinger's article, not to your question.  Sorry about not changing
the Subject: heading.

>All in all, I feel as if I am but a foolish boy who has unknowingly awakened 
>RODAN, MOTHRA, and GODZILLA and now the focus centers on a battle of the titans 
>rather than 'the real role of the immune system.'

Do I get to be Godzilla? :)

>Moreover, I am distressed that no 'original' ideas or 
>questions were expressed 

I'm sorry we did not live up to your expectations, but I see nothing wrong
with discussing a rather significant re-evaluation of some of the basic
tenets of acquired immunity.   

>Perhaps it would be better to start with a more focused idea:
>     Why does the immune system even exist?

I don't know that this is more "focused", but the obvious (if "textbook"),
is that having some sort of immune system gives a multicellular organism
a selective advantage.  (Unfortunately, this is really the only answer one
can give to questions about why some adaptation survives the evolutionary
process).  There are lots of parasitic organisms out there, and any animal 
that wants to survive will need some way to deal with them.  This may be 
"innate" (as the immune systems of invertebrates, and some aspects of
our own immune system), or "acquired" (the part of the vertebrate immune 
system that includes T and B cells).  The "function" of both types of 
immunity is to protect the organism from undesirables such as bacteria, 
viruses, etc., they just use different strategies (detecting conserved, 
decidedly non-host components, vs. producing lots of randomized recognition
molecules and keeping only the ones found to be useful).  However, since 
evolution is not directed, it is unreasonable to expect more than "because it
improves the organism's chances at reproducing" in response to this sort of 
question.  One might as well ask, "Why does the endocrine system exist?"

Perhaps some better questions might be:

"What types of 'undesirables' are most effectively dealt with by various
 types of immune systems?  Might this affect the strategies adopted by 
 different organisms?"

"What are the basic principles that immune systems use to differentiate
 between the Good, the Bad, and the Irrelevant?" (This, of course, being the
 question addressed by our "disappointing" exchanges of "unoriginal" ideas)

"What are the weaknesses of different types of immune systems, and are there 
 evolutionary considerations that might have maintained some of these
 weaknesses (allergies, for example)?"
Or perhaps most interesting:

"How did the immune system come to exist - what pre-existing systems were
 modified, and what others had to be invented, in order to come up with the
 immune system we currently have?"

The answers to the last question might help to answer (or, in turn, derive
from some answers to) the previous questions.

>Open your minds, think for yourself, but most of all have fun.

For someone complaining about a lack of original ideas, I noticed that you
did not contribute any of your own.  What are *your* thoughts on the reasons
behind the evolution of an immune system?

Ken Frauwirth (MiSTie #33025)       _           _
frauwirt at       |_) *    |/ (_ |\ |
Dept. of Molec. & Cell Bio.        |_) | () |\ (_ | \|  
Univ. of Cal., Berkeley      "Yes, we have second bananas" - Torgo the White

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