title: Homeostatic maintenance of T cells and natural killer cells.
abstract: Homeostasis in the immune system encompasses the mechanisms governing maintenance of a functional and diverse pool of lymphocytes, thus guaranteeing immunity to pathogens while remaining self-tolerant. Antigen-naïve T cells rely on survival signals through contact with self-peptide-loaded major histocompatibility complex (MHC) molecules plus interleukin (IL)-7. Conversely, antigen-experienced (memory) T cells are typically MHC-independent and they survive and undergo periodic homeostatic proliferation through contact with both IL-7 and IL-15. Also, non-conventional γδ T cells rely on a mix of IL-7 and IL-15 for their homeostasis, whereas natural killer cells are mainly dependent on contact with IL-15. Homeostasis of CD4(+) T regulatory cells is different in being chiefly regulated by contact with IL-2. Notably, increased levels of these cytokines cause expansion of responsive lymphocytes, such as found in lymphopenic hosts or following cytokine injection, whereas reduced cytokine levels cause a decline in cell numbers.
authors.affiliation: Allergy Unit, Department of Dermatology, University Hospital Zurich, Gloriastrasse 31, Zurich, Switzerland. onur.boyman@uzh.ch
authors.forename: Onur
authors.initials: O
authors.lastname: Boyman
authors.forename: Carsten
authors.initials: C
authors.lastname: Krieg
authors.forename: Dirk
authors.initials: D
authors.lastname: Homann
authors.forename: Jonathan
authors.initials: J
authors.lastname: Sprent
mesh_terms: D016207:Cytokines / Q000378:metabolism / Q000502:physiology; D006706:Homeostasis; D007156:Immunologic Memory; D007694:Killer Cells, Natural / Q000276:immunology*; D018448:Models, Immunological; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D016207:Cytokines; D011948:Receptors, Antigen, T-Cell