MW3 DLC Content Collection 1 is at last arriving for PC on May 8th 2012, declared Infinity Ward in a recent tweet.
— Infinity Ward (@InfinityWard) April 27, 2012
Neither paid nor free variants of the Call of Duty Elite service are accessible for PC gamers, therefore not one of the post launch DLC content was introduced for PC thus far.
The Content Collection includes the very first six pieces of DLC released for the game. It contains 4 new mutliplayer maps Piazza, Liberation, Overwatch and Black Box as well 2 Specs Ops Missions "Black Ice" and "Negotiator."
No price has been established but it’s likely to cost 14.99$, just like for the consoles.