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
