|
|
|
|
|
|
|
||
Original Article |
peschon{at}immunex.com
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResults and DiscussionReferences |
|---|
Key Words: interleukin 15 • knockout mice • natural killer cells • CD8+ T lymphocytes • immunologic memory
Studies of mice carrying induced mutations within the IL-2/IL-15 system provide definitive evidence that IL-2 and IL-15 have unique roles in vivo 789101112. Mice lacking IL-2, IL-2R
To further explore the role of IL-15 in vivo, we generated C57BL/6 mice that are genetically deficient in IL-15. Gross histological analysis of IL-15–/– mice revealed no evidence of increased cellular apoptosis or generalized defects in mast cells, muscle, or bone. However, the phenotypes of mice lacking either IL-15 (described here) or IL-15R
The IL-15–/– mice used throughout these studies were bred at Immunex and maintained on a C57BL/6 genetic background. All mice were housed under specific pathogen-free conditions and were used between 9 and 20 wk of age. Age- and sex-matched littermates (IL-15+/+ or IL-15+/–) or C57BL/6 mice (Taconic Farms, Inc.) were used as controls as indicated. Initial studies revealed no apparent difference between IL-15+/+ and IL-15+/– mice in cellularity of their secondary lymphoid tissues, phenotype of spleen or LN cells, or splenic NK cell responses.
Blood and Serum Analyses.
Histological Analyses.
Immunohistochemistry.
Cell Preparation.
Antibodies and Flow Cytometry.
In Vivo Treatment with Polyinosilic-Polycytidylic Acid or IL-15.
Analysis of NK Cell Function.
Viral Infections.
Introduction
Top
Abstract
Introduction
Materials and Methods
Results and Discussion
References
The cytokine IL-15 was discovered as a result of its "IL-2–like" stimulatory activity on T cells 12. The similar in vitro activities of IL-2 and IL-15 stem from shared use of common receptor signaling subunits. IL-15 and IL-2 both interact with receptor complexes that contain the common gamma (
c) and IL-2Rβ chains. The c subunit is also used for signaling by IL-4, IL-7, and IL-9 3, whereas the IL-2Rβ subunit is used for signaling only by IL-2 and IL-15 45. The ability of a cell to respond to IL-2 or IL-15 can also be controlled by the presence or absence of specific receptor subunits for IL-2 or IL-15. These distinct (nonshared) receptors, known as IL-2R
and IL-15R, respectively, do not appear to be involved in signaling but are required for high-affinity binding of these cytokines. Thus, despite the fact that IL-2 and IL-15 share receptor subunits used for signaling, differential expression of the IL-2R or IL-15R receptor subunits allows the two cytokines to exert qualitatively and/or quantitatively differential effects on several cell types. In addition, IL-2 and IL-15 are produced by different cells and in different tissues. Thus, the in vivo responses to IL-2 and IL-15 are likely to be temporally and physically compartmentalized (for a review, see reference 6). , or IL-2Rβ develop an autoimmune disorder. However, IL-2Rβ2/– mice have additional defects that are not observed in mice lacking IL-2 or IL-2R. These additional defects include an absence of functional NK cells and dramatic decreases in numbers of NK T cells and intestinal intraepithelial lymphocytes (IELs) that are believed to develop extrathymically. The differences in the phenotypes of mice lacking IL-2, IL-2R, or IL-2Rβ led to the speculation that IL-2 plays a primary role in maintaining homeostasis of thymus-derived T cells, whereas IL-15 promotes extrathymic development and survival of T cells and NK cells (for a review, see reference 13). More recent studies in normal mice indicate that IL-15 is a selective growth factor for memory CD8+, but not CD4+, T cells 14. Other studies implicate IL-15 as an anabolic factor for muscle cells 15, a differentiation factor for osteoclast progenitors 16, a growth factor for mast cells and intestinal epithelial cells 1718, and a general inhibitor of apoptosis in T cells, B cells, and fibroblasts 19. 20 confirm a critical role for IL-15 in regulating the development and/or expansion of NK cells, NK T cells, and distinct IEL populations. In addition, both of these strains of mice reveal a role for IL-15 in the maintenance of the memory phenotype CD8+ T cell population. IL-15–/– mice should prove useful for studying the roles of IL-15 in infectious disease, antitumor immunity, autoimmune responses, and inflammation.
Materials and Methods
Top
Abstract
Introduction
Materials and Methods
Results and Discussion
References
Mice.
C57BL/6 mice genetically deficient in IL-15 were generated by homologous recombination in embryonic stem (ES) cells. The structure of the murine IL-15 genomic locus has been described 21. A gene targeting vector was constructed in which a 7.5-kb SpeI-EcoRV fragment containing IL-15 exons 3–5, encoding amino acids 1–65 of the primary translation product, was replaced with a PGK-neo cassette. A thymidine kinase cassette (MC-TK) was inserted into the 5' end of the vector. C57BL/6-derived ES cells were electroporated with the IL-15 targeting vector and selected in G418 and ganciclovir as described 22. ES cell clones carrying a targeted IL-15 gene were identified by a combination of PCR and genomic Southern blot analyses and were injected into BALB/c blastocysts. Resulting male chimeras were bred to C57BL/6 females. The offspring were analyzed for germline transmission of the mutant IL-15 allele by PCR and genomic Southern blot analyses. Mice heterozygous for the IL-15 mutation (IL-15+/–) were intercrossed to generate IL-15–deficient (IL-15–/–) mice.
Peripheral blood was harvested by cardiac puncture, and blood smears were prepared. Complete blood counts and serum chemistry analyses were conducted by Phoenix Laboratory for Veterinarians (Everett, WA) using a CellDyne 3500 blood analyzer and a Hitachi chemistry analyzer. Basal levels of serum IgA, IgG, and IgM were determined by isotype-specific ELISA as described 23.
Mice were killed by exposure to CO2 and weighed. A midline incision was made through the skin but not into the abdominal wall, and 8 ml of sterile HBSS was injected into the peritoneal cavity. The abdomen was gently massaged, the fluid was extracted, and the cells were counted. To evaluate mast cells, quadruplicate 100 µl aliquots of fluid were diluted to 106 cells/ml and centrifuged onto slides at 500 rpm for 5 min using a Shandon Cytospin® II. All tissues were examined grossly, and 37 tissues representing all major tissues of all organ systems (skin and special senses, nervous, respiratory, digestive, urogenital, endocrine, lymphoid, hematopoietic, and musculoskeletal systems) were collected for histopathology. Tissues were fixed in 10% neutral buffered formalin, processed and embedded in paraffin, sectioned at 4 µm, and stained with hematoxylin and eosin. Body weight and selected absolute organ weights were determined, and relative organ to body weight ratios were calculated for spleen, thymus, and LNs.
Spleen, inguinal and mesenteric LNs, and thymus were quick-frozen in 2-methyl butane cooled with dry ice. A panel of anti–mouse immunophenotypic markers for T cells, B cells, macrophages, follicular dendritic cells, and germinal centers were applied to 5-µm cryosections cut onto charged slides. The reagents and protocols used are described in detail elsewhere 24.
Single cell suspensions of liver, thymus, spleen, and LN were prepared by gently pressing the tissues through fine nylon or wire mesh screens. Erythrocytes were depleted from spleen cell suspensions by hypotonic lysis. Intrahepatic mononuclear cells were separated from hepatocytes by density centrifugation over Lympholyte M (Cedarlane) as described 12. IELs were obtained from the small intestine and isolated on discontinuous Percoll (Pharmacia Fine Chemicals) gradients as described 25.
Expression of cell surface markers was analyzed by standard two or three-color flow cytometry on FACScaliburTM and FACScanTM II instruments (Becton Dickinson) and with CELLQuestTM software (Becton Dickinson). FITC-, PE-, and biotin-conjugated mAbs and isotype-matched controls were purchased from PharMingen. Secondary reagents to detect binding of biotinylated mAb included streptavidin-allophycocyanin (Molecular Probes), streptavidin-RED670 (GIBCO BRL), and streptavidin-CyChrome (PharMingen).
Mice were injected intraperitoneally with 0.2 ml pyrogen-free PBS or PBS containing either polyinosilic-polycytidylic acid (polyI:C) or human IL-15. PolyI:C-treated mice received a single injection of 100 µg polyI:C (Sigma Chemical Co.). IL-15–treated mice received 10 µg human IL-15 once daily for 7 d. Chinese hamster ovary (CHO)-derived human rIL-15 was produced and purified at Immunex. Endotoxin levels were <3.7 ng/mg of protein. The IL-15 for injection was prepared daily from a concentrated stock solution. Spleens and/or LNs were harvested 24 h after the last injection of PBS, polyI:C, or IL-15.
A chromium release assay was used to assess the cytolytic function of splenocytes from naive or treated mice. RBC-free splenocytes from individual mice were used as effector cells and incubated overnight in 96-well flat-bottomed plates in the presence of 5 x 103 51Cr-labeled YAC-1 or P815 target cell lines. There were four replicates per sample. Cell-free supernatants were harvested using a Skatron harvester. Spontaneous release (from targets incubated without effector cells) and maximum release (from targets incubated in the presence of 1% NP-40) were also determined. The percentage of specific lysis was calculated as: (experimental release – spontaneous release/maximum release – spontaneous release) x 100.
The neurotropic wild-type WR strain of vaccinia virus 26 was prepared and titered on CV-1 cells using standard techniques 27. Virus stocks were dispersed by sonication and diluted in endotoxin-free saline. 8-wk-old female mice were infected intravenously with 106 PFU of virus. Mice were observed daily for signs of morbidity and mortality.
Results and Discussion
Top
Abstract
Introduction
Materials and Methods
Results and Discussion
References
Generation and Gross Characterization of IL-15–/– Mice.
Mice genetically deficient in IL-15 were generated by homologous recombination in ES cells using the construct depicted in Fig. 1 A. Correct targeting of the IL-15 locus was confirmed by genomic Southern blot analysis (Fig. 1 B). Although reagents for detecting murine IL-15 protein are not available, the IL-15 mutation is expected to represent a null mutation, as it deletes the initiation codon, the leader sequence, and the first 17 amino acids of the mature protein. IL-15–/– mice were generated from IL-15+/– intercrosses at the expected Mendelian frequency, did not display any gross phenotypic anomalies, and had normal life spans in a specific pathogen-free facility (data not shown).
|
Thymic, Splenic, and LN Weight and Cellularity.
Within the course of these studies, we noted no consistent or marked difference in the size or the cellularity of the spleens, thymi, or peripheral LNs between small groups of age- and sex-matched IL-15–/– and littermate control (either IL-15+/+ or IL-15+/–) mice. To compare the groups in a quantitative fashion, the lymphoid organs were removed and weighed from a cohort of age-matched male mice (n = 17–18/group). There were no significant differences in the average absolute weights or organ to body weight ratios of the spleens or thymi between IL-15–/– and their heterozygote littermate controls (Fig. 2 A, and data not shown). However, the average absolute weight and organ to body weight ratio of the peripheral LNs from IL-15–/– mice were significantly lower than those of the controls (Fig. 2 B, and data not shown). To compare cellularity of these organs, data were pooled from numerous experiments. Although groups of mice were age and sex matched within each experiment, the pooled data samples were derived from both male and female mice between 9 and 20 wk of age (Fig. 2C and Fig. D). The pooled data revealed a significant decrease in the average cellularity of the peripheral LNs, but not the spleen or thymi, between IL-15–/– mice and the controls.
|
|
14 and preferential usage of Vβ8, V8β2, and Vβ7 (for a review, see reference 28). NK T cells are present in normal numbers in IL-2–/– mice 1112. In contrast, NK T cells are present, but dramatically reduced in number, in mice lacking either IL-2Rβ, IL-15R 1120, or IL-15 (Fig. 3b and Fig. c). The lower number of NK T cells in the IL-15–/– thymus was not likely due to a defect in selection, as the NK T cells that were present exhibited the skewed Vβ repertoire expected of such cells (Fig. 3 C). Additionally, IL-15–/– thymocytes exhibited normal expression and function of CD1d (data not shown), which is the antigen-presenting molecule that positively selects NK T cells 293031. This observation provides additional evidence that the basic elements required for NK T cell selection remain intact in IL-15–deficient mice. The observation that the NK T cells present in IL-15–/– mice appear to have undergone a normal selection process suggests that IL-15 is not obligatory for NK T cell differentiation but is important for expansion/survival or functional maturation of committed NK T cells.
IL-15 Deficiency Affects Selected IEL Subpopulations.
IEL subsets were examined to determine whether IL-15 is required for development or expansion of specific subsets of IELs. In normal mice, the IEL compartment consists of heterogenous populations of TCR-/β+ and TCR-/
+ T cells. The development or maturation of certain IEL subsets requires an intact thymus or factors that are produced by thymic-dependent T cell populations. Most "thymic-dependent" populations of IELs express Thy1 and are TCR-/β+CD8β+ or TCR-/β+CD4+. In contrast, most of the IELs that are thought to mature extrathymically (possibly within the gut epithelium itself) are Thy1– and bear TCR-/β or TCR-/ in conjunction with CD8 3233.
IELs were isolated from individual C57BL/6 or IL-15–/– mice, and cell yields were determined. Once isolated, the IEL populations from individual mice were pooled and analyzed by three-color flow cytometry for expression of various cell surface markers. The absolute number of CD3+ IELs isolated from IL-15–/– mice was estimated to be approximately twofold lower than that of control mice. Within the CD3+ populations, the ratio of /β to / IELs was 
1:1 in control and 2:1 in IL-15–/– mice (data not shown). Thy1– IELs, which made up 50% of IEL populations in control mice (Fig. 4A and Fig. C), accounted for <5% of the total IELs in IL-15–/– mice (Fig. 4B and Fig. D). Within gated populations of TCR-/β+ IELs, there were increases in the relative proportions of CD4+CD8– and CD4+CD8+ IELs in IL-15–/– mice compared with the controls (Fig. 4E and Fig. F). However, as the yield of CD3+ IELs from IL-15–/– mice was approximately twofold lower than that of control mice, the changes in the relative proportions of these IEL populations likely arise solely from a decrease in the absolute number of TCR-/β+ CD4–CD8+ IELs in IL-15–/– mice compared with controls. The decrease in the TCR-/β+CD4–CD8+ IEL population in IL-15–/– mice resulted from a selective decrease in the subset of IELs that express the CD8 homodimer (Fig. 4G and Fig. H). Thus, IL-15–/– mice have a dramatic reduction in the specific IEL populations that are thought to arise or mature independently of the thymus.
|
2/– mice 1020. It has been suggested that the abnormal IEL profile in IL-2Rβ2/– mice might be due to defects in activation-induced cell death that promote the preferential outgrowth and accumulation of thymic-dependent IEL populations within the gut epithelia, rather than due to a decrease in expansion or survival of thymic-independent IEL populations 34. However, the decreases in the relative proportions of Thy1– IELs and TCR-/β+CD8+ IEL populations in IL-15–/– mice (Fig. 4) were very similar to those observed in IL-2Rβ2/– mice 10. In addition, the absolute number of IELs isolated from IL-15R2/– mice is reduced approximately twofold and the relative proportions of CD8+ and TCR-/+ IELs are reduced three- to fourfold compared with controls 20. The selective reduction of these particular subsets of IELs in IL-15–/– and IL-15R2/– mice, neither of which appear to have defects in activation-induced cell death, points to a critical role for IL-15 in the development or maintenance of IEL populations that mature extrathymically.
IL-15–/– Mice Have a Reversible NK Cell Defect.
Flow cytometric analysis of splenocytes from naive IL-15–/– mice revealed that they had a severe reduction or absence of cells with an NK (NK1.1+CD3–) phenotype (data not shown). To determine whether IL-15–/– mice lacked functional splenic NK cells, their splenocytes were tested for cytolytic activity against NK-sensitive targets. Splenocytes from PBS-treated control mice exhibited low to weak NK activity, whereas splenocytes from polyI:C-treated control mice exhibited strong NK activity (Fig. 5 A). In contrast, splenocytes from IL-15–/– mice exhibited no demonstrable spontaneous or polyI:C-inducible NK activity.
|
Both control and IL-15–/– mice responded to IL-15 treatment with similar increases (1.5–2-fold) in splenic cellularity and similar phenotypic changes in splenic populations (Fig. 5 C, and data not shown). Both groups of IL-15–treated mice had dramatic increases (>12-fold) in their absolute numbers of splenic NK cells. In addition, the absolute numbers of splenic NK T and CD8+ T cells increased by approximately three- to fivefold in both groups. In contrast, the treatment had no effect on the absolute numbers of splenic B or CD4+ T cells (data not shown).
In vitro studies provide strong evidence that IL-15 is required for the later stages of NK cell maturation and acquisition of cytolytic activity 3738. However, further studies are needed to determine whether IL-15 reverses the functional NK cell defect in IL-15–/– mice by expanding and activating a severely reduced population of mature NK cells and/or by driving the proliferation and maturation of NK cell precursors.
IL-15–/– Mice Have a Reversible Defect in Memory Phenotype CD8+ T Cells.
Splenocytes and peripheral LN cells were analyzed for cell surface expression of lymphoid and myeloid cell surface markers (CD3
, CD4, CD8, CD11b, CD19, CD45, Gr1, Ter119, and NK1.1). No dramatic differences were noted in the relative proportions of B cells, macrophages, granulocytes, or CD4+ T cells between IL-15–/– and control mice (Table , and data not shown). In contrast, the relative proportions of splenic and LN CD8+ T cells were reduced approximately twofold in IL-15–/– mice compared with their littermate controls (Table ).
|
Three-color flow cytometry was used to analyze spleen and LN cells for the expression of CD8, CD4, and CD44. In IL-15–/– mice, there was a dramatic reduction in the relative proportion of CD44hiCD8+ cells in both the spleen (Fig. 6 A) and LN (data not shown) compared with the controls. The CD44hi population accounted for 19 ± 2% of CD8+ splenocytes and 14.2 ± 2% of CD8+ LN cells in control mice but only 6.5 ± 0.5% of CD8+ splenocytes and 2.8 ± 0.2% of CD8+ LN cells in IL-15–/– mice. In contrast, the relative proportion of CD44hi cells within the CD4+ population was similar in controls and IL-15–/– mice in both spleen (22.2 ± 2 vs. 22 ± 1%, respectively; Fig. 6 B) and LN (10.6 ± 0.4 vs. 11 ± 1%).
|
|
|
2/– Mice.2/– mice 20. The phenotypes of IL-15R2/– and IL-15–/– mice appear similar in terms of their NK, NK T, IEL, and peripheral CD8+ T cell defects. The observation that the defects in IL-15–/– mice are not more severe than those observed in IL-15R2/– mice suggests that the high-affinity IL-15R is required for normal physiological responses to IL-15.
Interestingly, the phenotypes that are observed in IL-15–/– and IL-15R2/– mice are not identical. IL-15–/– mice, like IL-2Rβ2/– mice 842, appear to have normal CD4+ and CD8+ thymic T cell development (Fig. 3). In contrast, IL-15R2/– mice may have impaired development of CD8+ T cells, as young mice exhibit an increased ratio of single positive CD4+ to CD8+ thymocytes and a slight thymic hypocellularity (25% decrease relative to controls). In addition, IL-15R2/– mice are markedly lymphopenic (30–80% decreased cellularity compared with controls), whereas IL-15–/– mice exhibited only a slight degree of lymphopenia (15% decrease in average weight and 29% decrease in average cellularity of LNs relative to controls; Fig. 2B and Fig. D). Elucidation of the mechanism(s) behind these phenotypic differences will require a systematic comparison of IL-15–/– and IL-15R2/– mice that are of matched genetic backgrounds and housed under identical conditions.
IL-15–/– mice will likely prove useful for defining the role of IL-15 (and/or IL-15–dependent cell populations) in host defense mechanisms against various pathogens, tumors, and allografts. In particular, the ability to rescue the NK and memory phenotype CD8+ T cell defects in IL-15–/– mice provides an ideal means by which to further dissect the in vivo relationship between IL-15 and these cell populations. When used in conjunction with appropriate animal models of disease, these mice should also prove useful for determining whether dysregulated expression of IL-15 contributes to the pathogenesis of acute or chronic autoimmune and inflammatory diseases.
|
Acknowledgments |
|---|
Funding for S. Joyce was provided by National Institutes of Health grant AI42284 and by the Juvenile Diabetes Foundation International, NY.
Submitted: 5 November 1999
Revised: 22 December 1999
Accepted: 23 December 1999
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResults and DiscussionReferences |
|---|
Giri J.G., Anderson D.M., Kumaki S., Park L.S., Grabstein K.H. & Cosman D.. IL-15, a novel T cell growth factor that shares activities and receptor components with IL-2, J. Leukoc. Biol., 57, 1995, 763–766.[Abstract]
Burton J.D., Bamford R.N., Peters C., Grant A.J., Kurys G., Goldman C.K., Brennan J., Roessler E. & Waldmann T.A.. A lymphokine, provisionally designated interleukin T and produced by a human adult T-cell leukemia line, stimulates T-cell proliferation and the induction of lymphokine-activated killer cells, Proc. Natl. Acad. Sci. USA., 91, 1994, 4935–4939.
Leonard W.J., Shores E.W. & Love P.E.. Role of the common cytokine receptor chain in cytokine signaling and lymphoid development, Immunol. Rev., 148, 1995, 97–114.[Medline]
Giri J.G., Ahdieh M., Eisenman J., Shanebeck K., Grabstein K., Kumaki S., Namen A., Park L.S., Cosman D. & Anderson D.. Utilization of the β and chains of the IL-2 receptor by the novel cytokine IL-15, EMBO (Eur. Mol. Biol. Organ.) J., 13, 1994, 2822–2830.[Medline]
Carson W.E., Giri J.G., Lindemann M.J., Linett M.L., Ahdieh M., Paxton R., Anderson D., Eisenman J., Grabstein K. & Caligiuri M.A.. Interleukin (IL) 15 is a novel cytokine that activates human natural killer cells via components of the IL-2 receptor, J. Exp. Med., 180, 1994, 1395–1403.
Kennedy M.K., Park L.S. & Paxton R.J.. Interleukin-15, Thomson A.. The Cytokine Handbook, 1998, 443–464, Academic Press, San Diego.
Kündig T.M., Schorle H., Bachmann M.F., Hengartner H., Zinkernagel R.M. & Horak I.. Immune responses in interleukin-2-deficient mice, Science., 262, 1993, 1059–1061.
Suzuki H., Kündig T.M., Furlonger C., Wakeman A., Timms E., Matsuyama T., Schmits R., Simard J.J.L., Ohashi P.S. & Griesser H.. Deregulated T cell activation and autoimmunity in mice lacking interleukin-2 receptor β, Science., 268, 1995, 1472–1476.
Willerford D.M., Chen J., Ferry J.A., Davidson L., Ma A. & Alt F.W.. Interleukin-2 receptor chain regulates the size and content of the peripheral lymphoid compartment, Immunity., 3, 1995, 521–530.[Medline]
Suzuki H., Duncan G.S., Takimoto H. & Mak T.W.. Abnormal development of intestinal intraepithelial lymphocytes and peripheral natural killer cells in mice lacking the IL-2 receptor β chain, J. Exp. Med., 185, 1997, 499–505.
Ohteki T., Ho S., Suzuki H., Mak T.W. & Ohashi P.S.. Role for IL-15/IL-15 receptor β-chain in natural killer 1.1+ T cell receptor-β+ cell development, J. Immunol., 159, 1997, 5931–5935.[Abstract]
Boesteanu A., De Silva A.D., Nakajima H., Leonard W.J., Peschon J.J. & Joyce S.. Distinct roles for signals relayed through the common cytokine receptor chain and interleukin 7 receptor chain in natural T cell development, J. Exp. Med., 186, 1997, 331–336.
Di Santo J.P.. Cytokinesshared receptors, distinct functions, Curr. Biol., 7, 1997, R424–R426.[Medline]
Zhang X., Sun S., Hwang I., Tough D.F. & Sprent J.. Potent and selective stimulation of memory-phenotype CD8+ T cells in vivo by IL-15, Immunity., 8, 1998, 591–599.[Medline]
Quinn L.S., Haugk K.L. & Grabstein K.H.. Interleukin-15a novel anabolic cytokine for skeletal muscle, Endocrinology., 136, 1995, 3669–3672.[Abstract]
Ogata Y., Kukita A., Kukita T., Komine M., Miyahara A., Miyazaki S. & Kohashi O.. A novel role of IL-15 in the development of osteoclastsinability to replace its activity with IL-2, J. Immunol., 162, 1999, 2754–2760.
Tagaya Y., Burton J.D., Miyamoto Y. & Waldmann T.A.. Identification of a novel receptor/signal transduction pathway for IL-15/T in mast cells, EMBO (Eur. Mol. Biol. Organ.) J., 15, 1996, 4928–4939.[Medline]
Reinecker H.-C., MacDermott R.P., Mirau S., Dignass A. & Podolsky D.K.. Intestinal epithelial cells both express and respond to interleukin 15, Gastroenterology., 111, 1996, 1706–1713.[Medline]
Bulfone-Paus S., Ungureanu D., Pohl T., Lindner G., Paus R., Rückert R., Krause H. & Kunzendorf U.. Interleukin-15 protects from lethal apoptosis in vivo, Nat. Med., 3, 1997, 1124–1128.[Medline]
Lodolce J.P., Boone D.L., Chai S., Swain R.E., Dassopoulos T., Trettin S. & Ma A.. IL-15 receptor maintains lymphoid homeostasis by supporting lymphocyte homing and proliferation, Immunity., 9, 1998, 669–676.[Medline]
Anderson D.M., Johnson L., Glaccum M.B., Copeland N.G., Gilbert D.J., Jenkins N.A., Valentine V., Kirstein M.N., Shapiro D.N. & Morris S.W.. Chromosomal assignment and genomic structure of Il15, Genomics., 25, 1995, 701–706.[Medline]
Peschon J.J., Torrance D.S., Stocking K.L., Glaccum M.B., Otten C., Willis C.R., Charrier K., Morrissey P.J., Ware C.B. & Mohler K.M.. TNF receptor-deficient mice reveal divergent roles for p55 and p75 in several models of inflammation, J. Immunol., 160, 1998, 943–952.
Renshaw B.R., Fanslow W.C. III, Armitage R.J., Campbell K.A., Liggitt D., Wright B., Davison B.L. & Maliszewski C.R.. Humoral immune responses in CD40 ligand–deficient mice, J. Exp. Med., 180, 1994, 1889–1900.
Dougall W.C., Glaccum M., Charrier K., Rohrbach K., Brasel K., De Smedt T., Daro E., Smith J., Tometsko M.E. & Maliszewski C.R.. RANK is essential for osteoclast and lymph node development, Genes Dev., 13, 1999, 2412–2424.
Morrissey P.J., Charrier K., Horovitz D.A., Fletcher F.A. & Watson J.D.. Analysis of the intra-epithelial lymphocyte compartment in SCID mice that received co-isogeneic CD4+ T cells. Evidence that mature post-thymic CD4+ T cells can be induced to express CD8 in vivo, J. Immunol., 154, 1995, 2678–2686.[Abstract]
Wokatsch R.. Vaccinia virus, Majer M.A. & Plotkin S.A., Strains of Human Viruses, 1972, 241–257, S. Karger, Basel.
Earl, P.L., N. Cooper, and B. Moss. 1991. Preparation of cell cultures and vaccinia virus stocks. In Current Protocols in Molecular Biology. F.M. Ausubel, R. Brent, R.E. Kingston, D.D. Moore, J.A. Seidman, J.A. Smith, and K. Struhl, editors. John Wiley & Sons, Inc., New York. 16.16.11–16.16.17.
MacDonald H.R.. Development and function of natural killer 1+ T cells, Biochem. Soc. Trans., 25, 1997, 696–699.[Medline]
Chen Y.H., Chiu N.M., Mandal M., Wang N. & Wang C.R.. Impaired NK1+ T cell development and early IL-4 production in CD1-deficient mice, Immunity., 6, 1997, 459–467.[Medline]
Mendiratta S.K., Martin W.D., Hong S., Boesteanu A., Joyce S. & Van Kaer L.. CD1d1 mutant mice are deficient in natural T cells that promptly produce IL-4, Immunity., 6, 1997, 469–477.[Medline]
Smiley S.T., Kaplan M.H. & Grusby M.J.. Immunoglobulin E production in the absence of interleukin-4-secreting CD1-dependent cells, Science., 275, 1997, 977–979.
Viney J.L., MacDonald T.T. & Kilshaw P.J.. T-cell receptor expression in intestinal intra-epithelial lymphocyte subpopulations in normal and athymic mice, Immunology., 66, 1989, 583–587.[Medline]
Rocha B., Vassalli P. & Guy-Grand D.. Thymic and extrathymic origins of gut intraepithelial lymphocyte populations in mice, J. Exp. Med., 180, 1994, 681–686.
Di Santo J.P., Colucci F. & Guy-Grand D.. Natural killer and T cells of innate and adaptive immunitylymphoid compartments with different requirements for common chain-dependent cytokines, Immunol. Rev., 165, 1998, 29–38.[Medline]
Evans R., Fuller J.A., Christianson G., Krupke D.M. & Troutt A.B.. IL-15 mediates anti-tumor effects after cyclophosphamide injection of tumor-bearing mice and enhances adoptive immunotherapythe potential role of NK cell subpopulations, Cell. Immunol., 179, 1997, 66–73.[Medline]
Munger W., DeJoy S.Q., Jeyaseelan R. Sr., Torley L.W., Grabstein K.H., Eisenman J., Paxton R., Cox T., Wick M.M. & Kerwar S.S.. Studies evaluating the antitumor activity and toxicity of interleukin-15, a new T cell growth factorcomparison with interleukin-2, Cell. Immunol., 165, 1995, 289–293.[Medline]
Puzanov I.J., Williams N.S., Schatzle J., Sivakumar P.V., Bennett M. & Kumar V.. Ontogeny of NK cells and the bone marrow microenvironmentwhere does IL15 fit in?, Res. Immunol., 148, 1997, 195–201.[Medline]
Williams N.S., Klem J., Puzanov I.J., Sivakumar P.V., Schatzle J.D., Bennett M. & Kumar V.. Natural killer cell differentiationinsights from knockout and transgenic mouse models and in vitro systems, Immunol. Rev., 165, 1998, 47–61.[Medline]
Karupiah G., Woodhams C.E., Blanden R.V. & Ramshaw I.A.. Immunobiology of infection with recombinant vaccinia virus encoding murine IL-2. Mechanisms of rapid viral clearance in immunocompetent mice, J. Immunol., 147, 1991, 4327–4332.[Abstract]
Buller R.M. & Palumbo G.J.. Poxvirus pathogenesis, Microbiol. Rev., 55, 1991, 80–122.
Ruby J. & Ramshaw I.. The antiviral activity of immune CD8+ T cells is dependent on interferon-gamma, Lymphokine Cytokine Res., 10, 1991, 353–358.[Medline]
Suzuki H., Hayakawa A., Bouchard D., Nakashima I. & Mak T.W.. Normal thymic selection, superantigen-induced deletion and Fas-mediated apoptosis of T cells in IL-2 receptor β chain-deficient mice, Int. Immunol., 9, 1997, 1367–1374.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| TABLE OF CONTENTS |
|
