If you are immune to something this means you are not affected by a disease.
How do we become immune?
The dead or inactive form of a pathogen is inserted in to your body. white blood cells produce antibodies which will recognise the antigen(protien shape). white blood cells known aslymphocytes help to protect you aginst disease such as producing anti-toxins which deactivate the antigen making it harmless .Lymphocyes produce antibodies and anti-toxins. white blood cells know as phagocytes engulf (surrounding the bacteria) and then ingest the bacteria so you don't get the disease.