I too heard/read about this.
I am O, but I don't remember if I am - or +. I'd have to look. But throughout my life I have noticed I do not get as sick as many friends/family members. I have been described as "hardy"
My exception is bronchitis. Whenever I have a cold, it immediately moves to my lungs and I end up with pretty bad bronchitis. Usually happens once a year, sometime around November - February.