Immune system

Immunity (legal), conferring a status on a person or body that makes that person or body free from otherwise legal obligations such as, for example, liability for damages or punishment for criminal acts

Use immunity, under which the government may not use a witness's grand jury testimony to prosecute that person (but if the state acquires evidence for a crime independent of the testimony, the witness can then be prosecuted)

Immunity (medical), a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion, and is related to the functions of the immune system