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David L Boone

Publications and source records attributed to David L Boone.

14 recordsLinked to original sources
PubMed2004

Coordinate expression and trans presentation of interleukin (IL)-15Ralpha and IL-15 supports natural killer cell and memory CD8+ T cell homeostasis.

The high affinity interleukin (IL)-15 receptor, IL-15Ralpha, is essential for supporting lymphoid homeostasis. To assess whether IL-15Ralpha's role in vivo is to trans present IL-15, we generated mixed bone marrow chimera from IL-15Ralpha- and IL-2/15Rbeta-deficient mice. We find that IL-15Ralpha-competent, IL-2/15Rbeta-deficient cells are able to support IL-15Ralpha-deficient natural killer (NK) and memory CD8+ T cells, thus ruling out secondary signals on these cells and demonstrating that IL-15Ralpha-mediated presentation of IL-15 in trans is the primary mechanism by which IL-15Ralpha functions in vivo. Surprisingly, using IL-15- and IL-15Ralpha-deficient mixed chimera, we also find that IL-15 and IL-15Ralpha must be expressed by the same cells to present IL-15 in trans, indicating that IL-15Ralpha is required on a cellular level for the elaboration of IL-15. These studies indicate that IL-15Ralpha defines homeostatic niches for NK and memory CD8+ T cells by controlling both the production and the presentation of IL-15 in trans to NK and CD8+ memory T cells.

Animals↗
PubMed2004

Cutting edge: murine dendritic cells require IL-15R alpha to prime NK cells.

NK cells protect hosts against viral pathogens and transformed cells, and dendritic cells (DCs) play important roles in activating NK cells. We now find that murine IL-15Ralpha-deficient DCs fail to support NK cell cytolytic activity and elaboration of IFN-gamma, despite the fact that these DCs express normal levels of costimulatory molecules and IL-12. By contrast, IL-15Ralpha expression on NK cells is entirely dispensable for their activation by DCs. In addition, blockade with anti-IL-15Ralpha and anti-IL-2Rbeta but not anti-IL-2Ralpha-specific Abs prevents NK cell activation by wild-type DCs. Finally, presentation of IL-15 by purified IL-15Ralpha/Fc in trans synergizes with IL-12 to support NK cell priming. These findings suggest that murine DCs require IL-15Ralpha to present IL-15 in trans to NK cells during NK cell priming.

Animals↗
PubMed2004

The ubiquitin-modifying enzyme A20 is required for termination of Toll-like receptor responses.

A20 is a cytoplasmic protein required for the termination of tumor necrosis factor (TNF)-induced signals. We show here that mice doubly deficient in either A20 and TNF or A20 and TNF receptor 1 developed spontaneous inflammation, indicating that A20 is also critical for the regulation of TNF-independent signals in vivo. A20 was required for the termination of Toll-like receptor-induced activity of the transcription factor NF-kappaB and proinflammatory gene expression in macrophages, and this function protected mice from endotoxic shock. A20 accomplished this biochemically by directly removing ubiquitin moieties from the signaling molecule TRAF6. The critical function of this deubiquitinating enzyme in the restriction of TLR signals emphasizes the importance of the regulation of ubiquitin conjugation in innate immune cells.

Animals↗
PubMed2004

De-ubiquitination and ubiquitin ligase domains of A20 downregulate NF-kappaB signalling.

NF-kappaB transcription factors mediate the effects of pro-inflammatory cytokines such as tumour necrosis factor-alpha and interleukin-1beta. Failure to downregulate NF-kappaB transcriptional activity results in chronic inflammation and cell death, as observed in A20-deficient mice. A20 is a potent inhibitor of NF-kappaB signalling, but its mechanism of action is unknown. Here we show that A20 downregulates NF-kappaB signalling through the cooperative activity of its two ubiquitin-editing domains. The amino-terminal domain of A20, which is a de-ubiquitinating (DUB) enzyme of the OTU (ovarian tumour) family, removes lysine-63 (K63)-linked ubiquitin chains from receptor interacting protein (RIP), an essential mediator of the proximal TNF receptor 1 (TNFR1) signalling complex. The carboxy-terminal domain of A20, composed of seven C2/C2 zinc fingers, then functions as a ubiquitin ligase by polyubiquitinating RIP with K48-linked ubiquitin chains, thereby targeting RIP for proteasomal degradation. Here we define a novel ubiquitin ligase domain and identify two sequential mechanisms by which A20 downregulates NF-kappaB signalling. We also provide an example of a protein containing separate ubiquitin ligase and DUB domains, both of which participate in mediating a distinct regulatory effect.

Cell Line↗
PubMed2003

Escherichia coli LPS induces heat shock protein 25 in intestinal epithelial cells through MAP kinase activation.

Protection of colonic epithelial integrity and function is critical, because compromises in mucosal functions can lead to adverse and potentially life-threatening effects. The gut flora may contribute to this protection, in part, through the sustained induction of cytoprotective heat shock proteins (HSPs) in surface colonocytes. In this study, we investigated whether Escherichia coli LPS mediates bacteria-induced HSP by using cultured young adult mouse colon (YAMC) cells, an in vitro model of the colonic epithelium. E. coli LPS led to an epithelial cell-type specific induction of HSP25 in a time- and concentration-dependent manner, an effect that did not involve changes in HSP72. YAMC cells expressed the toll-like receptors (TLR)2 and TLR4 but not the costimulatory CD14 molecule. Whereas LPS stimulated both the p38 and ERK1/2 but not the stress-activated protein kinase/c-Jun NH(2)-terminal kinase, signaling pathways in the YAMC cells, all three were stimulated in RAW macrophage cells (in which no LPS-induced HSP25 expression was observed). The p38 inhibitor SB-203580 and the MAP kinase kinase-1 inhibitor PD-98059 inhibited HSP25 induction by LPS. LPS treatment also conferred protection against actin depolymerization induced by the oxidant monochloramine. The HSP25 dependence of the LPS protective effect was outlined in inhibitor studies and through adenovirus-mediated overexpression of HSP25. In conclusion, LPS may be an important mediator of enteric bacteria-induced expression of intestinal epithelial HSP25, an effect that may contribute to filamentous actin stabilization under physiological as well as pathophysiological conditions and thus protection of colonic epithelial integrity.

Actins↗
PubMed2003

Fas is not essential for lamina propria T lymphocyte homeostasis.

IL-2 receptor alpha-deficient (IL2Ralpha-/-) mice spontaneously accumulate vast numbers of intestinal lamina propria (LP) T cells and develop bowel inflammation. The accumulation of T cells in IL2Ralpha-/- mice is thought to result, in part, from defective Fas-induced cell death. To understand the role of cell proliferation and death in regulating LP T cells in IL2Ralpha-/- mice, we have directly examined the proliferation and Fas sensitivity of wild-type, lpr/lpr, and IL2Ralpha-/- LP T cells. In wild-type mice, 5'-bromodeoxyuridine (BrdU) labeling and Fas susceptibility are greatest in CD44Hi LP T cells. Fas-deficient lpr/lpr mice have normal total numbers of LP T cells, despite an increased proportion of BrdU+ T cells. By contrast, IL2Ralpha-/- mice possess increased total numbers of LP T cells, despite normal proportions of BrdU+ LP T cells. Finally, wild-type and IL2Ralpha-/- LP T cells are equivalently Fas sensitive. These results demonstrate that LP T cells proliferate and are Fas-sensitive cells. IL2Ralpha-/- mice accumulate a large number of these Fas-sensitive LP T cells and clearly differ from Fas-deficient lpr/lpr mice in this regard. Thus our studies reveal that Fas is dispensable for LP T cell homeostasis and suggest that the intestinal inflammation observed in IL2Ralpha-/- mice is independent of defective Fas-induced cell death.

Animals↗
PubMed2003

Interleukin (IL)-15R[alpha]-deficient natural killer cells survive in normal but not IL-15R[alpha]-deficient mice.

Natural killer (NK) cells protect hosts against viral pathogens and transformed cells. IL-15 is thought to play a critical role in NK cell development, but its role in the regulation of peripheral NK cells is less well defined. We now find that adoptive transfer of normal NK cells into mice lacking the high affinity interleukin (IL)-15 receptor, IL-15Ralpha, surprisingly results in the abrupt loss of these cells. Moreover, IL-15Ralpha-deficient NK cells can differentiate successfully in radiation bone marrow chimera bearing normal cells. Finally, adoptively transferred IL-15Ralpha-deficient NK cells survive in normal but not IL-15Ralpha-deficient mice. These findings demonstrate that NK cell-independent IL-15Ralpha expression is critical for maintaining peripheral NK cells, while IL-15Ralpha expression on NK cells is not required for this function.

Adoptive Transfer↗
PubMed2003

IL-15R alpha expression on CD8+ T cells is dispensable for T cell memory.

The generation and maintenance of immunological memory requires the activation, expansion, and persistent proliferation of antigen-specific T cells. Recent work suggests that IL-15 may be important for this process. Surprisingly, we now find that expression of the high-affinity receptor for IL-15, IL-15R alpha, on T cells is dispensable for the generation or maintenance of memory CD8(+) T cells. By contrast, IL-15R alpha expression on cells other than T cells is absolutely critical for this function. These findings may be related to IL-15R alpha's ability to present IL-15 in trans to low-affinity IL-15R beta gamma(c) receptors on memory CD8(+) T cells. These unexpected results provide insights into how IL-15R alpha supports memory CD8(+) T cells.

Adjuvants, Immunologic↗
PubMed2003

Enteric flora and lymphocyte-derived cytokines determine expression of heat shock proteins in mouse colonic epithelial cells.

BACKGROUND & AIMS: Inducible heat shock proteins (hsps), particularly hsp25 and hsp72, are expressed by surface colonocytes and may have a role in protecting intestinal epithelial cells against injury. This study is aimed at determining if enteric bacteria and/or immune signals regulate their physiologic expression. METHODS: Intestinal hsp25, hsp72, and constitutive hsc73 expression were studied in immunodeficient RAG-1(-/-) mice and in normal mice. Mucosal permeability was measured by mannitol flux and transepithelial resistance. Hsp expression in intestinal YAMC cells was assessed after incubation with recombinant cytokines, activated lamina propria lymphocytes (LPLs), or Bacteroides fragilis. RESULTS: Chronic metronidazole treatment decreases colonic mucosal hsp25 and hsp72 expression, an effect associated with increased susceptibility of mucosal barrier function to C. difficile toxin A. Hsp expression also was increased in YAMC cells incubated with B. fragilis, an effect mediated by lipopolysaccharide and other bacteria-derived factors. Colonic hsp72, but not hsp25 or hsc73, expression is decreased in RAG-1(-/-) mice. Recombinant IL-2 and other cytokines enhance YAMC hsp25 and/or hsp72 expression. Activated LPLs induce YAMC hsp expression, an effect blocked by IL-2 neutralizing antibody. CONCLUSIONS: Enteric flora and mucosal lymphocytes play a role in maintaining physiologic expression of colonocyte hsp25 and hsp72.

Animals↗
PubMed2002

Regulation of lymphoid homeostasis by interleukin-15.

Interleukin (IL)-15 is a member of the common gamma chain family of cytokines, and is closely related to IL-2. While these two cytokines share several important biological functions in vitro, recent mouse models have demonstrated unique roles for these two cytokines in supporting lymphoid homeostasis in vivo. IL-15 has been shown to regulate the homeostasis of both innate and adaptive immune cells, and this review will discuss several ways in which this pleiotropic cytokine may support lymphoid homeostasis.

Animals↗
PubMed2002

Interleukin-2-deficient mice develop colitis in the absence of CD28 costimulation.

The intestinal lamina propria contains lymphocytes that are chronically activated by exposure to luminal antigens. Dysregulation of these cells is thought to be central to the pathogenesis of bowel inflammation in experimental models of inflammatory bowel disease. CD28 signals on peripheral T cells provide important costimulatory signals that enhance T-cell proliferation and activation responses to antigens. However, the role of CD28 signals in lamina propria T cells or models of inflammatory bowel disease have not been determined. Accordingly, we examined T lymphocyte activation and proliferation in CD28-deficient (CD28-/-) mice to examine the in vivo roles of CD28 signals in lamina propria T-cell homeostasis. We further generated CD28-/- interleukin (IL)-2-/- double mutant mice to assess the role of CD28 signals in supporting the spontaneously activated and pathogenic T cells that accumulate in IL-2-/- mice. CD28-/- lamina propria T cells displayed reduced activation markers, but were present in normal numbers and proliferated normally. IL-2-/- lymphocytes expressed high levels of bcl-xL, whereas CD28-/- IL-2-/- cells had substantially less bcl-xL. However, lymphadenopathy and ulcerative colitis-like disease occurred in both IL-2-/- and CD28-/- IL-2-/- mice. Thus, CD28 provides a functional costimulatory signal to lamina propria T cells but is not required for homeostasis of these cells. In addition, neither CD28 nor bcl-xL appears to be required for the spontaneous accumulation of T cells in IL-2-/- mice. This suggests that other costimulatory molecules or T-cell receptor ligation alone drive lymphocyte expansion in IL-2-deficient mice.

Animals↗