IgE

Japanese: IgE

(1) IgE
The most important molecule involved in allergic reactions, especially immediate allergies, is IgE. In 1921, Prausnitz and Küstner discovered that when serum from an allergic patient was injected into the skin of a healthy person, an immediate allergen-induced reaction could be induced locally. This reaction came to be called the Prausnitz-Küstner reaction (PK reaction), and the transferred reactant was called reagin. The nature of reagin remained unknown for a long time, but in 1966, Ishizaka Kiminari and Teruko proved that it was a new antibody that exists in very low concentrations, and named IgE after the initials of erythema. Meanwhile, the receptor (FcεRI) that binds IgE with high affinity was cloned at the end of the 1980s, and it was found to be a tetrameric structure (αβγ ₂ ) consisting of three types of subunits, α, β, and γ. IgE is important not only for causing allergic reactions, but also as a therapeutic target molecule. The biologic anti-IgE antibody omalizumab (a humanized antibody that recognizes the Cε3 binding site with FcεRI in the IgE molecule and binds only to free IgE, so as not to cross-link IgE on mast cells (Figure 10-22-3)) has been found to be effective against asthma and allergic rhinitis, and is used clinically in Japan, Europe, and the United States for severe allergic asthma. [Yamaguchi Masao]
■ References
Barnes PJ: New therapies for asthma: is there any progress? Trends Pharmacol Sci, 31: 335-343, 2010.
Hsu FI, Boyce JA: Biology of mast cells and their mediators. In: Allergy: Principles and Practice, 7th ed (Adkinson NF Jr, Bochner BS, et al eds), pp311-328, Mosby, Philadelphia, 2009.
Luo, Zhijing: Mast cells: from the front line of defense against infection to allergies. Allergy (edited by Yamamoto, Kazuhiko), p55-63, Asakura Publishing, 2002.

Figure 10-22-3
Binding of omalizumab to free IgE

Figure 10-22-3

Source : Internal Medicine, 10th Edition About Internal Medicine, 10th Edition Information

Japanese:

（1）IgE
　アレルギー反応，特に即時型アレルギーに関与する最も重要な分子はIgEである．1921年にPrausnitzとKüstnerはアレルギー患者の血清を健常人の皮膚に注入すると，その局所においてアレルゲンによる即時型反応が誘発可能になることを発見した．この反応はPrausnitz-Küstner反応（P-K反応），移入される反応物質はレアギン（reagin）とよばれるようになった．その後，レアギンの本態は長く不明であったが，1966年に石坂公成・照子夫妻により非常に低濃度で存在する新たな抗体であることが証明され，erythemaの頭文字をとってIgEと命名された．一方，IgEを高親和性に結合する受容体（FcεRI）は1980年代の終わりにクローニングされ，α，β，γの3種類のサブユニットからなる四量体構造（αβγ₂）であることが明らかとなった．IgEはアレルギー反応を引き起こすだけでなく，治療標的分子としても重要である．生物製剤である抗IgE抗体オマリズマブ（マスト細胞上のIgEを架橋刺激しないよう，IgE分子のうちでFcεRIとの結合部位Cε3を認識し遊離IgEにのみ結合するヒト化抗体を用いている（図10-22-3））療法が喘息やアレルギー性鼻炎に有効であることが判明し，わが国や欧米ではアレルギー性重症喘息を対象に臨床で用いられている．［山口正雄］
■文献
Barnes PJ: New therapies for asthma: is there any progress? Trends Pharmacol Sci, 31: 335-343, 2010.
Hsu FI, Boyce JA: Biology of mast cells and their mediators. In: Allergy: Principles and Practice, 7th ed (Adkinson NF Jr, Bochner BS, et al eds), pp311-328, Mosby, Philadelphia, 2009.
羅　智靖：マスト細胞：感染防御の最前線からアレルギーまで．アレルギー病学（山本一彦編），p55-63，朝倉書店，2002.

図10-22-3
遊離IgE に対するオマリズマブの結合">

図10-22-3

出典　内科学第10版内科学第10版について　情報

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