All immunity is natural, because your immune system is natural.
It is acquired either through infection or vaccination. Infection has more side effects, many of which are very bad and one of which is death.
Naturally, I choose to acquire my immunity through vaccination.
@lucentbeam I went overboard on 360, I have the Reach console and the Halo 4 console, my dad found my see through Halo4 controller in the basement.
Reach was probably still my favorite though.
@xK1@harl37 Some aspects were worse than what drew me to love fallout 3 but in its own right some changes were nice. I didnt play any of the DLC for 4 though.