Natural killer (NK) cells hold fundamental roles in the body's response to cancer, infection, autoimmunity, allergy and pregnancy. Given the significant and wide-ranging function of NK cells, gaining a deeper understanding of their basic immunological functions provides us with a larger body of material to translate to therapeutic approaches in combating disease. Recently in the NK cell biology field, there has been a overwhelming increase in our basic understanding of NK cell functioning. The use of NK cell-based immunotherapies to enhance the medical treatment of disease is very promising. Despite this promise, a significant amount of work remains to be done before these therapies are at a point where they can be used as a prevalent form of treatment.