positive negative Selection

HI Ehd123, you mean in terms of genetics? I've included something that might help as an attachment. Let me know what happens.

Hey padre
Thank you for the article, but now it's not genetics... It's something got to do with techniques to select for cells 

Oh right! Then I remember doing this in immunology class.

It has to do with T cells as they mature, right?

In the thymus, the immature T cells (the thymocytes), must productively rearrange their TCR genes so they can express a functional TCR (αβ or γδ).

αβ TCR+ T cells need to commit to expressing either CD4 or CD8

They must survive positive selection, that is, it allows for “useful” T cells to be selected for and expanded in number. They must survive negative selection, this allows for “dangerous” T cells to be removed.

Here's what I used to learn it before

Now I see where positive and negative came from 

That was a great animation! Seen something similar for microarrays though *sound wise and all*

Thank you so much! Greatly appreciated 

NP