Is there a way to curb reaction aggression?

Does he do this when off leash or just on leash? Larger breeds can becom very territorial when it come to their family and possessions. sometimes this behavior is instilled by the other dog who is an aggressor and your dog goes into protection mode. when you are around other dogs, pay attention to how they approach you and your dog, look for different movements in the face, and eyes. This is how dogs communicate. they other dog may be giving off signals that they want to dominate your dog or that they are aggressive. To add to that you have a female dog that he considers his and he will protect her against another dog.

Maybe getting him into some special training for dogs that have aggression issues will help.