Something unknowable in immunology? Simple logic?

Ken Frauwirth frauwirt at mendel.Berkeley.EDU
Thu Jan 20 20:48:30 EST 1994

In article <2hn1ui$m72 at netnews.upenn.edu>, dfonseca at mail.sas.upenn.edu (Dina Fonseca) writes:
|> A recent post stated:
|> I can see that the rate of antigen experience by T cells is 
|> greatest when younger, but this ignores the fact that new TcR and Ig
|> are generated right up until the day you die.  Since antigen receptor
|>  generation is essentially a random process it is inevitable
|> that cells with self-reactive receptors will emerge from the bone marrow
|>  all throughout life. If the thymus involutes after
|> puberty, where are all these new cells getting their education
|>  (both in +ve and -ve selection)?
|> Is this really a problem? If the thymus involutes, then 
|> no T cells will be made i.e. no positive selection.
|> As no T cells are made, it does'nt matter that there
|> is no negative selection either.

I think the problem occurs because new T cells *are* produced throughout
a person's lifetime.  At least, that is the belief, since T cells die and
must be replaced.  It is hypothesized that the T cells may be "educated"
in alternative lymphoid organs, such as the spleen, after the involution
of the thymus.  In fact, I have been told that thymectomized mice still 
produce mature T cells, although in exceedingly small numbers.

Ken Frauwirth                  BBB   IIIII    OO    K  K   EEEEE   N   N
frauwirt at mendel.berkeley.edu   B  B    I     O  O   K K    E       NN  N
Dept. of Molec. & Cell Bio.    BBB     I     O  O   KK     EEEE    N N N
Immunology Division            B  B    I     O  O   K K    E       N  NN
Univ. of Cal., Berkeley        BBB   IIIII    OO    K  K   EEEEE   N   N

"Later, at Cal, Berkeley..." "Free Huey!" "Kill the pigs!" - from T-AS

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