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Peanut Glycolipid Antigens Activate Natural Killer T Cells Causing Severe Allergy


The long-term goal of this project is to better define peanut allergens, and to identify the properties of peanuts that result in the high prevalence of peanut sensitization, the failure of peanut allergy to resolve over time, and explain the disproportionate number of severe episodes of peanut induced anaphylaxis. <P>We hypothesize that peanuts contain lipid and lipid-carbohydrate complexes that activate innate immune mechanisms, providing adjuvant effects, which greatly enhance peanut specific adaptive immune responses. We will examine lipid complexes from peanuts, and their capacity to activate natural killer T (NKT) cells, which are known to respond to glycolipids and to contribute significantly to adaptive immunity and to inflammatory diseases such as infectious diseases, autoimmunity, cancer and asthma. <P>We have previously shown that NKT cells at mucosal sites play a critical role in the development of airway inflammation and asthma. In addition, we have shown that glycolipids from the bacterial species Sphingomonas can directly activate pulmonary NKT cells and induce airway inflammation and airway hyper-reactivity, a cardinal feature of asthma. <P>These results suggest that NKT cells in mucosal tissues may respond to agents such as microbes and plant products containing glycolipids, and that NKT cells could play a previously unsuspected but critical role in regulating many immune responses in mucosal tissues to environmental glycolipids. Although only a few glycolipids are currently known to activate NKT cells, we believe that some foods, such as peanuts, may contain glycolipids that can stimulate NKT cells, resulting in the activation of innate and adaptive mucosal immune responses. We therefore propose to purify and identify glycolipids from peanuts that can directly activate NKT cells. <P>We believe that peanut glycolipids can activate NKT cells, thereby activating innate immune mechanisms that then greatly enhance adaptive immunity to peanuts. We will study murine systems, as well as human cells from normal and peanut allergic individuals, examining both in vitro and in vivo responses. <P>We are working with an outstanding lipid biochemist, and have extensive experience working with human and murine NKT cells. Moreover, we already have exciting preliminary data demonstrating that purified peanut glycolipids can indeed activate NKT cells, suggesting that our hypothesis is correct, and that our studies are feasible and likely to generate important new information. <P>We believe that our studies are likely to greatly expand the fundamental understanding of the types of immune responses that occur at mucosal sites, and how foods, such as peanuts, can induce immune responses that result in food allergy.

Umetsu, Dale
Children's Hospital - Boston
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