The Brood is where calling Wolverine simply immune can give the wrong impression of what happens to him.

The Brood is where calling Wolverine simply immune can give the wrong impression of what happens to him. In Uncanny X-Men #162, he's infected, he's in pain and the transformation begins. His healing factor eventually beats the embryo, but he has to go through that experience first. It gets far enough to be a very real threat to him. And once he's survived it, he still has the rest of the team to worry about. They don't all have his healing factor. Being able to get the thing out of his own body doesn't tell him how to save everybody else. Then the Brood story in Denver, #232–234, puts him through another struggle. Reverend Connover helps him through that part of the fight, and again you're watching Logan trying to hold on while his body deals with what's happening. So the ability is doing something impressive, but it isn't keeping the whole experience from happening. He can be infected, he can suffer, and he can look like he's losing before his body manages to overcome it.