title: IL-7 and IL-15: biology and roles in T-Cell immunity in health and disease.
abstract: Cytokines IL-7 and IL-15 are essentially involved in T-cell homeostasis. IL-7 is required for developing mature T cells in the thymus, whereas in the periphery, it promotes the survival of naïve and memory T cells by upregulating the antiapoptotic molecule Bcl-2. IL-15 potently induces the proliferation of memory CD8+ T cells independently of antigen and augments their effector function. Although IL-7 and IL-15 may help to defend the host against microorganisms and tumors by promoting T-cell immunity, dysregulated production of IL-7 and IL-15 can be harmful. In fact, increased levels of IL-15 in the circulation and inflamed tissues have been reported in various autoimmune diseases, including rheumatoid arthritis (RA), possibly contributing to the pathogenesis. In addition, IL-7, which may induce the production of inflammatory cytokines from T cells and monocytes, are found to be elevated in the joints of patients with RA. Here, we review what is currently known about the roles of these cytokines in T-cell immunity, in general, as well as in RA, in particular, focusing on recent discoveries.
authors.affiliation: Section of Rheumatology, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520 USA.
authors.forename: Hang-Rae
authors.initials: HR
authors.lastname: Kim
authors.forename: Kyung-A
authors.initials: KA
authors.lastname: Hwang
authors.forename: Sung-Hwan
authors.initials: SH
authors.lastname: Park
authors.forename: Insoo
authors.initials: I
authors.lastname: Kang
mesh_terms: D000818:Animals; D001172:Arthritis, Rheumatoid / Q000209:etiology / Q000276:immunology; D006801:Humans; D019409:Interleukin-15 / Q000276:immunology*; D015851:Interleukin-7 / Q000276:immunology*; D053647:Receptors, Interleukin-15 / Q000502:physiology; D020395:Receptors, Interleukin-7 / Q000502:physiology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D019409:Interleukin-15; D015851:Interleukin-7; D053647:Receptors, Interleukin-15; D020395:Receptors, Interleukin-7