title: Reconstitution of early lymphoid proliferation and immune function in Jak3-deficient mice by interleukin-3.
abstract: Expansion of early lymphoid progenitors requires interleukin-7 (IL-7), which functions through gamma(c)-mediated receptor activation of Jak3. Jak3 deficiency is a cause of severe combined immunodeficiency (SCID) in humans and mice. IL-3 activates many of the same signaling pathways as IL-7, such as Stat5, but achieves this effect through the activation of Jak2 rather than Jak3. We hypothesized that expansion of an IL-7-responsive precursor population through a Jak3-independent pathway using IL-3 may stimulate early lymphoid progenitors and restore lymphopoiesis in Jak3(-/-) mice. Newborn Jak3(-/-) mice that were injected with IL-3 demonstrated thymic enlargement, a 2- to 20-fold increase in thymocyte numbers, and up to a 10-fold expansion in the number of CD4(+), CD8(+), and B220(+)/IgM(+) splenic lymphocytes, consistent with an effect upon an early lymphoid progenitor population. In contrast to control mice, IL-3-treated Jak3(-/-) mice challenged with the allogeneic major histocompatibility complex (MHC) class I-bearing tumor P815 developed a specific CD8-dependent cytotoxic T lymphocyte (CTL) response. IL-3-treated mice also mounted influenza-specific CTL responses and survival was prolonged. The beneficial effects of IL-3 are proposed to be produced by stimulation of a lymphoid precursor population of IL-7Ralpha(+)/IL-3Ralpha(+) cells that we identified in wild-type bone marrow. In vitro, we show that an early IL-7R(+) lymphoid progenitor population expresses IL-3R and proliferates in response to IL-3 and that IL-3 activates Stat5 comparably to IL-7. Clinically, IL-3 may therefore be useful treatment for X-linked and Jak3-deficient SCID patients who lack bone marrow donors.
authors.affiliation: Howard Hughes Medical Institute, Department of Biochemistry, St. Jude Children's Research Hospital, Memphis, TN, USA.
authors.forename: M P
authors.initials: MP
authors.lastname: Brown
authors.forename: T
authors.initials: T
authors.lastname: Nosaka
authors.forename: R A
authors.initials: RA
authors.lastname: Tripp
authors.forename: J
authors.initials: J
authors.lastname: Brooks
authors.forename: J M
authors.initials: JM
authors.lastname: van Deursen
authors.forename: M K
authors.initials: MK
authors.lastname: Brenner
authors.forename: P C
authors.initials: PC
authors.lastname: Doherty
authors.forename: J N
authors.initials: JN
authors.lastname: Ihle
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000276:immunology; D005434:Flow Cytometry; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000276:immunology*; D007377:Interleukin-3 / Q000502:physiology; D015851:Interleukin-7 / Q000502:physiology; D053616:Janus Kinase 3; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D016513:Mice, SCID; D011505:Protein-Tyrosine Kinases / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D020395:Receptors, Interleukin-7 / Q000235:genetics; D015398:Signal Transduction / Q000276:immunology
chemical_list: D007377:Interleukin-3; D015851:Interleukin-7; D020395:Receptors, Interleukin-7; D011505:Protein-Tyrosine Kinases; C507935:Jak3 protein, mouse; D053616:Janus Kinase 3