Jill Ford

ADAM10 is a principal 'sheddase' of the low-affinity immunoglobulin E receptor CD23

CD23, the low-affinity immunoglobulin E receptor, is an important modulator of the allergic response and of diseases such as rheumatoid arthritis. The proteolytic release of CD23 from cells is considered a key event in the allergic response. Here we used loss-of-function and gain-of-function experiments with cells lacking or overexpressing candidate CD23-releasing enzymes (ADAM8, ADAM9, ADAM10, ADAM12, ADAM15, ADAM17, ADAM19 and ADAM33), ADAM-knockout mice and a selective inhibitor to identify ADAM10 as the main CD23-releasing enzyme in vivo. Our findings provide a likely target for the treatment of allergic reactions and set the stage for further studies of the involvement of ADAM10 in CD23-dependent pathologies.

IL-10 Suppresses Mast Cell IgE Receptor Expression and Signaling In Vitro and In Vivo

Mast cells are known for their roles in allergy, asthma, systemic anaphylaxis, and inflammatory disease. IL-10 can regulate inflammatory responses and may serve as a natural regulator of mast cell function. We examined the effects of IL-10 on in vitro-cultured mouse and human mast cells, and evaluated the effects of IL-10 on FcεRI in vivo using mouse models. IgE receptor signaling events were also assessed in the presence or absence of IL-10. IL-10 inhibited mouse mast cell FcεRI expression in vitro through a Stat3-dependent process. This down-regulation was consistent in mice tested in vivo, and also on cultured human mast cells. IL-10 diminished expression of the signaling molecules Syk, Fyn, Akt, and Stat5, which could explain its ability to inhibit IgE-mediated activation. Studies of passive systemic anaphylaxis in IL-10-transgenic mice showed that IL-10 overexpression reduced the IgE-mediated anaphylactic response. These data suggest an important regulatory role for IL-10 in dampening mast cell FcεRI expression and function. IL-10 may hence serve as a mediator of mast cell homeostasis, preventing excessive activation and the development of chronic inflammation.

Soluble Trem-like Transcript-1 Regulates Leukocyte Activation and Controls Microbial Sepsis

The triggering receptor expressed on myeloid cells (TREM)-1 plays a crucial role during the onset of sepsis by amplifying the host immune response. The TREM-like transcript-1 (TLT-1) belongs to the TREM family, is selectively expressed on activated platelets, and is known to facilitate platelet aggregation through binding to fibrinogen. In this study, we show that a soluble form of TLT-1 is implicated in the regulation of inflammation during sepsis by dampening leukocyte activation and modulating platelet-neutrophil crosstalk. A 17-aa sequence of the TLT-1 extracellular domain (LR17) is responsible for this activity through competition with the TREM-1 ligand. Whereas early or late LR17 treatment of septic mice improves survival, treml-1−/− animals are highly susceptible to polymicrobial infection. The present findings identify platelet-derived soluble TLT-1 as a potent endogenous regulator of sepsis-associated inflammation and open new therapeutic perspectives. We anticipate soluble TLT-1 to be important in regulating leukocyte activation during other noninfectious inflammatory disorders.

A potential new target for asthma therapy: a disintegrin and metalloprotease 10 (ADAM10) involvement in murine experimental asthma.

To cite this article: Mathews JA, Ford J, Norton S, Kang D, Dellinger A, Gibb DR, Ford AQ, Massay H, Kepley CL, Scherle P, Keegan AD, Conrad DH. A potential new target for asthma therapy: A Disintegrin and Metalloprotease 10 (ADAM10) involvement in murine experimental asthma. Allergy 2011; 66: 1193–1200.

129/SvJ mice have mutated CD23 and hyper IgE

CD23, the low affinity IgE receptor, is hypothesized to function as a negative regulator of IgE production. Upon discovering reduced CD23 surface levels in 129/SvJ inbred mice, we sought to further investigate 129/SvJ CD23 and to examine its influence on IgE levels. Five amino acid substitutions were found in 129/SvJ CD23. Identical mutations were also observed in CD23 from New Zealand Black and 129P1/ReJ mice. 129/SvJ B cells proliferated more rapidly than those from BALB/c after stimulation with IL-4 and CD40 ligand trimer. However, in vitro IgE levels in supernatants from stimulated 129/SvJ B cells were significantly reduced. Contrary to the in vitro findings, the 129/SvJ CD23 mutations correlated with a hyper IgE phenotype in vivo and 129/SvJ were able to clear Nippostrongylus brasiliensis infection more rapidly than either BALB/c or C57BL/6. Overall, this study further suggests that CD23 is an important regulatory factor for IgE production.

Implications for Gene Therapy-Limiting Expression of IL-2Rγc Delineate Differences in Signaling Thresholds Required for Lymphocyte Development and Maintenance

X-linked SCID patients are deficient in functional IL-2Rγc leading to the loss of IL-2/IL-4/IL-7/IL-9/IL-15/IL-21 signaling and a lack of NK and mature T cells. Patients treated with IL-2Rγc gene therapy have T cells develop; however, their NK cell numbers remain low, suggesting antiviral responses may be compromised. Similarly, IL-2Rγc−/− mice reconstituted with IL-2Rγc developed few NK cells, and reconstituted T cells exhibited defective proliferative responses suggesting incomplete recovery of IL-2Rγc signaling. Given the shift toward self-inactivating long terminal repeats with weaker promoters to control the risk of leukemia, we assessed NK and T cell numbers and function in IL-2Rγc−/− mice reconstituted with limiting amounts of IL-2Rγc. Reconstitution resulted in lower IL-2/-15–mediated STAT5 phosphorylation and proliferation in NK and T cells. However, TCR costimulation restored cytokine-driven T cell proliferation to wild-type levels. Vector modifications that improved IL-2Rγc levels increased cytokine-induced STAT5 phosphorylation in both populations and increased NK cell proliferation demonstrating that IL-2Rγc levels are limiting. In addition, although the half-lives of both NK and T cells expressing intermediate levels of IL-2Rγc are reduced compared with wild-type cells, the reduction in NK cell half-live is much more severe than in T cells. Collectively, these data indicate different IL-2Rγc signaling thresholds for lymphocyte development and proliferation making functional monitoring imperative during gene therapy. Further, our findings suggest that IL-2Rγc reconstituted T cells may persist more efficiently than NK cells due to compensation for suboptimal IL-2Rγc signaling by the TCR.

Abstract 1562: The G protein-coupled receptor mFPR2 promotes antitumor host defense

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FLnnmFPR2 is a G protein-coupled receptor interacting with chemotactic agonists produced by bacteria and the host. In vivo, mFPR2 plays a major role in innate and adaptive immune responses as shown by reduced severity of allergic airway inflammation and diminished production of Th1 and Th2 cytokines in mFPR2-deficient mice. These defects were associated with impaired trafficking of antigen presenting dendritic cells into the inflammatory sites and the draining lymph nodes. The aim of this study is to examine the role of mFPR2 in tumor progression. We found that mFPR2-deficient mice bearing subcutaneously implanted Lewis Lung Cancer cells (LLC) exhibited significantly shortened survival rate due to more rapidly growing tumors. In contrast, in mFPR2-transgenic (Tg) mice, subcutaneously implanted LLC tumors grew more slowly than those in wild type (WT) littermates. We further observed a decrease in the proportion of CD11b+ and Gr1+ myeloid cells accompanied by reduced infiltration of CD11b+Gr1low myeloid-derived suppressor cells and CD4+Foxp3+ regulatory T cells in LLC tumors in mFPR2-Tg mice. These results suggest that mFPR2 may play an important role in anti-tumor host defense by down-regulating immune suppressive cell infiltration in tumor tissues.nnCitation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1562. doi:10.1158/1538-7445.AM2011-1562