In article <32ttqj$13o at nermal.cs.uoguelph.ca>, gappleya at uoguelph.ca (Greg
Appleyard) says:
>>My question is, since T-cells do the self/non-self discrimination and
>such discrimination is made vigilent against intracellular infections
>through thymic education, how is it that self-specific T-cells exist
>normally in the periphery without rampant autoimmunity. The self-specific
>T-cells must be regulated, but how? It seems a paradox that self/non-self
>discrimination is made on the basis of selecting T-cells without
>self-reactivity (negative selection) and yet self-specific T-cells are
>part of the normal lymphocyte repertoire.
No paradox. Self-specific T-cells are part of the normal lymphocyte
repertoire because peptides from the corresponding intracellular self
proteins have not been presented in order to cause the deletion of the
self-specific T-cell clones. This is because there is an intracellular
mechanism for distinguishing self/not self. This mechanism is very
"primitive" in that it evolved before multicellular organisms evolved.
(J.Th.Biol. 167,7-12; J. Biol.Sys.2, in press). Some self peptides are
presented, and in these cases T cell deletion has occurred.
Sincerely, Don Forsdyke Discussion Leader
Bionet.immunology
