Here is a link to an excellent article looking at this question.
John 17:10-12 (English Standard Version)
10 All mine are yours, and yours are mine, and I am glorified in them. 11 And I am no longer in the world, but they are in the world, and I am coming to you. Holy Father, keep them in your name, which you have given me, that they may be one, even as we are one. 12 While I was with them, I kept them in your name, which you have given me. I have guarded them, and not one of them has been lost except the son of destruction, that the Scripture might be fulfilled.