A Central Role for Ly49 Receptors in NK Cell Memory

In the past decade, the study of NK cells was transformed by the discovery of three ways these "innate" immune cells display adaptive immune behavior, including the ability to form long-lasting, Ag-specific memories of a wide variety of immunogens. In this review, we examine these types of NK cell memory, highlighting their unique features and underlying similarities. We explore those similarities in depth, focusing on the role that Ly49 receptors play in various types of NK cell memory. From this Ly49 dependency, we will build a model by which we understand the three types of NK cell memory as aspects of what is ultimately the same adaptive immune process, rather than separate facets of NK cell biology. We hope that a defined model for NK cell memory will empower collaboration between researchers of these three fields to further our understanding of this surprising and clinically promising immune response.