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アレルギー反応：アナフィラキシー
アナフィラキシーは、免疫グロブリンE、略してIgEによって媒介される、重篤で生命を脅かす過敏反応です。IgEがアレルゲンに結合すると、肥満細胞および好塩基球からメディエーター（ヒスタミン、ロイコトリエン、プロスタグランジンなど）が放出されます。これらのメディエーターは血管拡張、浮腫、炎症を引き起こし…
アナフィラキシーは、IgE抗体によって媒介される即時の過敏反応です。これらの抗体はアレルゲンに結合し、アレルゲン-IgE抗体複合体を形成します。一般的なアレルゲンには花粉、ダニ、薬物、特定の食品が含まれます。
これらの複合体は肥満細胞や好塩基球の受容体に結合し、急速な脱顆粒化とヒスタミン、ロウコトリエン、プロスタグランジンの放出を引き起こします。
これらのメディエーターは血管拡張、気管支収縮、浮腫、好中球活性化を引き起こし、炎症反応を引き起こします。
これらの反応は血管系、消化管、皮膚、呼吸器系に深刻な影響を及ぼす可能性があります。また、食物アレルギー、蕁麻疹、鼻炎、喘息などの症状として現れることもあります。
ペニシリン、アスパラギナーゼ、モノクローナル抗体、コルチコトロピン、ヘパリン、ワクチン、局所麻酔薬、クロルヘキシジンなどの防腐剤など、さまざまな薬剤がアナフィラキシーを引き起こすことがあります。
アナフィラキシーの診断方法は症状に基づく臨床的です。ペニシロイルポリリシンの皮内注射などの皮膚検査は、後にペニシリンアレルギーを特定することができます。
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Q1: What is anaphylaxis and how does it develop?
Anaphylaxis is a severe, immediate hypersensitivity reaction mediated by IgE antibodies. When IgE binds to allergens, it forms complexes that attach to mast cells and basophils, triggering rapid degranulation. This releases mediators like histamine, leukotrienes, and prostaglandins, causing vasodilation, bronchoconstriction, edema, and inflammation throughout the body.
Q2: Which drugs commonly trigger anaphylactic reactions?
Penicillin is responsible for approximately 75% of anaphylactic deaths due to widespread use. Other drugs causing anaphylaxis include asparaginase, monoclonal antibodies, corticotropin, heparin, vaccines, local anesthetics, and antiseptics like chlorhexidine. These reactions occur through IgE-mediated mechanisms similar to food and environmental allergens.
Q3: What body systems are affected during anaphylaxis?
Anaphylaxis primarily affects the cardiovascular, respiratory, gastrointestinal, and integumentary systems. Symptoms include urticarial rash, hives, angioedema, bronchoconstriction, wheezing, shortness of breath, and hypotension. Severe cases progress to anaphylactic shock, characterized by sudden blood pressure drops, respiratory distress, and potential cardiovascular collapse.
Q4: How is anaphylaxis diagnosed in clinical practice?
Anaphylaxis diagnosis is primarily clinical, based on symptom presentation. Skin tests, such as intradermal injection of penicilloylpolylysine, can later identify penicillin allergy. Detecting particular IgE in plasma confirms allergic reactions, though these tests are reserved for cases where the allergen cause remains unclear.
Q5: What are common allergens that cause anaphylaxis?
Common allergens include food items like peanuts and shellfish, environmental substances such as grass pollen and dust mites, insect stings, and pharmaceutical agents. Radiological contrast agents, vaccines, and latex also trigger anaphylaxis. These allergens bind to IgE antibodies, initiating the cascade of mast cell and basophil degranulation.
Q6: What mediators are released during anaphylaxis and what effects do they produce?
Mast cells and basophils release histamine, leukotrienes, and prostaglandins upon degranulation. These mediators cause vasodilation, bronchoconstriction, edema, and neutrophil activation, generating an inflammatory response. The resulting cascade produces symptoms ranging from mild urticaria to life-threatening cardiovascular collapse and respiratory distress.
Q7: How does anaphylaxis differ from other hypersensitivity reactions?
Anaphylaxis is an immediate, IgE-mediated hypersensitivity reaction occurring within minutes of allergen exposure. Unlike delayed hypersensitivity reactions, which develop over hours or days, anaphylaxis causes rapid degranulation of mast cells and basophils. This distinguishes it from other hypersensitivity types in onset speed and severity.