T-cells -- Positive and Negative selection

[kl323]

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So I just had this question in Uworld asking you to ID the fate of the T cell undergoing maturation in the thymus.. I'm just confused over why my answer choice is wrong.

How is it possible to distinguish positive and negative selection if they tell you the T cell demonstrates high affinity interaction with MHC molecules on Thymic stromal cells?

Can anyone break it down for me? I definitely understand what positive and negative selection means. In fact, when I read MHC and T cell interaction, it steered me to my answer choice... which is wrong.

 

[whoknows2012]

So I just had this question in Uworld asking you to ID the fate of the T cell undergoing maturation in the thymus.. I'm just confused over why my answer choice is wrong.

How is it possible to distinguish positive and negative selection if they tell you the T cell demonstrates high affinity interaction with MHC molecules on Thymic stromal cells?

Can anyone break it down for me? I definitely understand what positive and negative selection means. In fact, when I read MHC and T cell interaction, it steered me to my answer choice... which is wrong.

positive selection occurs on thymic epithelial cells while negative selection occurs with APCs

 

[coffeeeandtea]

So I just had this question in Uworld asking you to ID the fate of the T cell undergoing maturation in the thymus.. I'm just confused over why my answer choice is wrong.

How is it possible to distinguish positive and negative selection if they tell you the T cell demonstrates high affinity interaction with MHC molecules on Thymic stromal cells?

Can anyone break it down for me? I definitely understand what positive and negative selection means. In fact, when I read MHC and T cell interaction, it steered me to my answer choice... which is wrong.

T cells that have high affinity interaction with MHC are deleted (negative selection) and only T cells with weak interaction are left. So in case any T cells become autoreactive, they will not have high affinity, only weak affinity.

 

[kl323]

I always thought that T cells are positively selected if they interact with the MHC molecules. On the other hand, I thought they would be negatively selected if they react w/ self-antigen.

I guess I didn't realize that MHC is considered a "self-antigen."

Thanks!