Antigens, Ly; Gene Expression Regulation; Killer Cells, Natural/metabolism; Lectins, C-Type; Receptors, Immunologic/biosynthesis; Animals; Antigens, CD/immunology; Chimera/immunology; Cytotoxicity, Immunologic; Gene Expression Regulation, Developmental; Genes, MHC Class I; Genomic Imprinting; Histocompatibility Antigens Class I/immunology; Histocompatibility Antigens Class II/immunology; Humans; Killer Cells, Natural/classification; Killer Cells, Natural/immunology; Macromolecular Substances; Membrane Glycoproteins/immunology; Mice; Mice, Knockout; Models, Immunological; NK Cell Lectin-Like Receptor Subfamily D; Receptors, Immunologic/genetics; Receptors, Immunologic/immunology; Receptors, KIR; Receptors, NK Cell Lectin-Like; Self Tolerance/immunology; Stochastic Processes; T-Lymphocyte Subsets/immunology