User blog comment:ImperiexSeed/Horsemen VS Angels/@comment-1509826-20120609210138/@comment-1509826-20120609212353

Well it can still cut them (the knife that is), when dean stabbed castiel with it, the knife went in, he simply didn't react. Besides, it wouldn't do much good, unless you cut there ring off, as they can't be killed.

I surpose they would be immune to pestilence's powers, but couldn't he infect there vessels?