Re: [asa] PSCF article on immune system

From: Don Nield <>
Date: Fri Dec 04 2009 - 14:42:39 EST

Bill Powers wrote:
> I have read the recent article by Craig Story on immunology, and I have a
> few comments.
> 1) The main thrust of the piece is to persuade us that "random" processes
> are essential in the vital functioning of the creation of antibodies.
> There are, he says, some 10^10 different antibody formations possible.
> This vast number of possibilities is accomplished with from only about 500
> gene segments. It is possible to generate such a large number of
> possibilities from so small a number of gene segments because the joining
> of these segments is imprecise and influenced by random processes.
> In this way Craig wants us to understand what a marvelous chemical machine
> is the antibody mechanism, and the essential necessary use of randomness
> to protect from a wide host of unseen pathogens.
> So here is my question, one Craig devotes very little time to, since it is
> not the primary focus of the article.
> With 10^10 possible antibodies, it would seem impossible for a random
> system to work. We would all die long before the appropriate antibodies
> were found in this haystack. This means that, while randomness may very
> well be a crucial part of the system, it cannot be the central governing
> process.
This is not a problem. One does not need the absolute optimum over the
10^10 possibilities. Anything that works sufficiently well will do.
Thus optimizing over a reasonably large subset of the possibilities is

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Received on Fri Dec 4 14:43:11 2009

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