As the research has continued, it has become increasingly clear that natural killer (NK) cells are critical sentinels of the innate immune response, playing important roles in protecting the body from numerous pathogens and cancer in addition to contributing to normal pregnancy and impacting the outcomes of transplantation. While the first edition provided a valuable collection of classical cellular and in vivo techniques to study NK cell functions, the Second Edition of "Natural Killer Cell Protocols: Cellular and Molecular Methods" brings together more recently developed methods, more refined techniques, and detailed protocols designed to study NK cells within specialized tissue sites in both mice and humans. In this collection of methods, international leaders in the field cover topics ranging from the analysis of the various stages of NK cell development and maturation to specialized techniques for the identification of ligands for NK cell receptors. This volume also includes an appendix, providing a rich resource summarizing available reagents to study NK cells, cross-referencing KIR nomenclature, and detailing the many HLA ligands for various KIR family members. As a volume in the highly successful Methods in Molecular Biology™ series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols, and thorough notes sections, highlighting tips on troubleshooting and avoiding known pitfalls.