When killers become helpers.

Since their initial characterization by Kiessling over 35 years ago, natural killer (NK) cells continue to constitute an area of intensive discovery in the immunology field. Although most of the research efforts concentrated on characterizing the role of NK cells in tumor prevention and fighting infection through the killing of dangerous cells, several recent findings highlight unexpected non-cytolytic functions of human and mouse NK cells. Such functions include promoting placental tissue development, antigen presentation and stimulation of T cells, priming of macrophages and dendritic cells, reducing transplant tissue rejection and several others.