Innocent question

[davewitley]

No spoilers here, though replies necessarily involve them.

I was looking again at GOF, and noticed that as Harry relates the 
adventure in the graveyard to Dumbledore, and mentions that a sample 
of his blood was required for the rebirthing potion, there is a 
momentary gleam of triumph in Dumbledore's eye.

Is there anything in HBP that casts light on what that is about?

David