DNA-Binding Proteins/physiology; Nerve Tissue Proteins/physiology; Nuclear Receptor Subfamily 4, Group A, Member 1/physiology; Nuclear Receptor Subfamily 4, Group A, Member 2/physiology; Receptors, Antigen, T-Cell/metabolism; Receptors, Steroid/physiology; Receptors, Thyroid Hormone/physiology; T-Lymphocytes, Regulatory/immunology; T-Lymphocytes, Regulatory/metabolism; Animals; Autoimmunity/genetics; Cell Differentiation; Cells, Cultured; DNA-Binding Proteins/genetics; Forkhead Transcription Factors/genetics; Forkhead Transcription Factors/metabolism; Genes, Immediate-Early; Homeostasis; Mice; Mice, Knockout; Nerve Tissue Proteins/genetics; Nuclear Receptor Subfamily 4, Group A, Member 1/genetics; Nuclear Receptor Subfamily 4, Group A, Member 2/genetics; Promoter Regions, Genetic; RNA Interference; RNA, Small Interfering; Receptors, Antigen, T-Cell/genetics; Receptors, Antigen, T-Cell/immunology; Receptors, Steroid/genetics; Receptors, Thyroid Hormone/genetics; Signal Transduction; T-Lymphocyte Subsets/immunology; T-Lymphocyte Subsets/metabolism; T-Lymphocytes, Regulatory/cytology; Thymocytes/metabolism