[cheryl j (OP)]

I believe that before birth and early in childhood the thymus is important in the maturation of T- lymphocytes, and their capacitiy to distingusih between self and non self, but I forget how it works. Are T cells that respond to self-antigens some how eliminated?Or do they never respond to self antigens?

[Nizzle]

T-cells that respond to self-antigens are indeed also formed and consequently eliminated, but that's about everything I remembered from my education. It had something to do with the "Major histocompatibility complex" but the exact mechanism should be out there on the interweb somewhere..