Nancy Wood

IL-33 synergizes with IgE-dependent and IgE-independent agents to promote mast cell and basophil activation

ObjectiveMast cell and basophil activation contributes to inflammation, bronchoconstriction, and airway hyperresponsiveness in asthma. Because IL-33 expression is inflammation inducible, we investigated IL-33-mediated effects in concert with both IgE-mediated and IgE-independent stimulation.MethodsBecause the HMC-1 mast cell line can be activated by GPCR and RTK signaling, we studied the effects of IL-33 on these pathways. The IL-33- and SCF-stimulated HMC-1 cells were co-cultured with human lung fibroblasts and airway smooth muscle cells in a collagen gel contraction assay. IL-33 effects on IgE-mediated activation were studied in primary mast cells and basophils.ResultIL-33 synergized with adenosine, C5a, SCF, and NGF receptor activation. IL-33-stimulated and SCF-stimulated HMC-1 cells demonstrated enhanced collagen gel contraction when cultured with fibroblasts or smooth muscle cells. IL-33 also synergized with IgE receptor activation of primary human mast cells and basophils.ConclusionIL-33 amplifies inflammation in both IgE-independent and IgE-dependent responses.

Interleukin-13 Neutralization by Two Distinct Receptor Blocking Mechanisms Reduces Immunoglobulin E Responses and Lung Inflammation in Cynomolgus Monkeys

Interleukin (IL)-13 is a key cytokine driving allergic and asthmatic responses and contributes to airway inflammation in cynomolgus monkeys after segmental challenge with Ascaris suum antigen. IL-13 bioactivity is mediated by a heterodimeric receptor (IL-13Rα1/IL-4Rα) and can be inhibited in vitro by targeting IL-13 interaction with either chain. However, in cytokine systems, in vitro neutralization activity may not always predict inhibitory function in vivo. To address the efficacy of two different IL-13 neutralization mechanisms in a primate model of atopic disease, two humanized monoclonal antibodies to IL-13 were generated, with highly homologous properties, differing in epitope recognition. Ab01 blocks IL-13 interaction with IL-4Rα, and Ab02 blocks IL-13 interaction with IL-13Rα1. In a cynomolgus monkey model of IgE responses to A. suum antigen, both Ab01 and Ab02 effectively reduced serum titers of Ascaris-specific IgE and diminished ex vivo Ascaris-triggered basophil histamine release, assayed 8 weeks after a single administration of antibody. The two antibodies also produced comparable reductions in pulmonary inflammation after lung segmental challenge with Ascaris antigen. Increased serum levels of IL-13, lacking demonstrable biological activity, were seen postchallenge in animals given either anti-IL-13 antibody but not in control animals given human IgG of irrelevant specificity. These findings demonstrate a potent effect of IL-13 neutralization on IgE-mediated atopic responses in a primate system and show that IL-13 can be efficiently neutralized by targeting either the IL-4Rα-binding epitope or the IL-13Rα1-binding epitope.

MMP dependence of fibroblast contraction and collagen production induced by human mast cell activation in a three-dimensional collagen lattice

Mast cell-fibroblast interactions may contribute to fibrosis in asthma and other disease states. Fibroblast contraction is known to be stimulated by coculture with the human mast cell line, HMC-1, or by mast cell-derived agents. Matrix metalloproteinases (MMPs) can also mediate contraction, but the MMP-dependence of mast cell-induced fibroblast contractility is not established, and the consequences of mast cell activation within the coculture system have not been fully explored. We demonstrate that activation of primary human mast cells (pHMC) with IgE receptor cross-linking, or activation of HMC-1 with C5a, enhanced contractility of human lung fibroblasts in a three-dimensional collagen lattice system. This enhanced contractility was inhibited by the pan-MMP antagonist, batimastat, and was transferrable in the conditioned medium of activated mast cells. Exogenously added MMPs promoted gel contraction by mediating the proteolytic activation of latent transforming growth factor-beta (TGF-beta). Consistent with this, fibroblast contraction induced by mast cell activation was enhanced by addition of excess latent TGF-beta to the cultures. Batimastat inhibited this response, suggesting that MMPs capable of activating latent TGF-beta were released following mast cell activation in coculture with fibroblasts. Collagen production was also stimulated by activated mast cells in an MMP-dependent manner. MMP-2 and MMP-3 content of the gels increased in the presence of activated mast cells, and inhibition of these enzymes blocked the contractile response. These findings demonstrate the MMP dependence of mast cell-induced fibroblast contraction and collagen production.