can I use a Dish Network Satellite dish to receive Directv if it is aimed proplerly?

There is a dish network satellite dish already mounted..can I use it to receive Directv signal if I align it to directv satellite?
To add...I have the directv receivers so that is not a problem..can I use the Dish network Dish eventhough it is bigger and has 3 lnbs? I just have the standard receivers..should I take off 2 of the lnbs..and does it matter which ones?