Anaes · Applied cardiovascular & respiratory physiology
Immunology basics
Also known as Immune system · Innate and adaptive immunity · Hypersensitivity · Anaphylaxis mechanism · Complement system · IgE-mediated allergy
The immune system defends against pathogens and tumours, and its disorders underlie the most dramatic anaesthetic emergency — anaphylaxis. The framework rests on five exam-critical ideas: the innate immune system (physical barriers, complement, phagocytes, natural killer cells) provides immediate, non-specific defence; the adaptive immune system (T lymphocytes for cell-mediated immunity, B lymphocytes for antibody-mediated humoral immunity) provides specific, memory-based defence; the complement system (classical, alternative and lectin pathways) opsonises pathogens, recruits inflammatory cells, and forms the membrane attack complex; hypersensitivity reactions are classified by the Gell and Coombs system into four types (Type I IgE-mediated immediate, Type II antibody-mediated cytotoxic, Type III immune-complex, Type IV delayed cell-mediated); and anaesthesia-induced anaphylaxis is a Type I IgE-mediated reaction in which a drug (most commonly a neuromuscular blocker) cross-links IgE on mast cells, triggering degranulation and the release of histamine, tryptase and leukotrienes that cause vasodilation, bronchospasm and cardiovascular collapse. Built on the NKT-cell study (Trujillo-Ocampo 2026), the vitamin D immuno-modulator study (Shende 2026), the perioperative anaphylaxis epidemiology review (Takazawa 2026), the remimazolam-anaphylaxis report (Jo 2026), the sugammadex-airway-oedema report (Habib 2026), and the IgE amplification loop review (Tanei 2026).
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- Anaesthesia-induced anaphylaxis is a Type I (IgE-mediated) hypersensitivity reaction; neuromuscular blocking agents, antibiotics and sugammadex are among the major culprits (JESPA nationwide prospective surveillance; sugammadex frequency higher in Japan reflecting extensive use).
- Mast-cell tryptase is the key diagnostic test; integrate clinical findings with tryptase using the EAACI consensus formula (1.2 x baseline + 2 ng/mL) plus skin testing, basophil activation tests or drug provocation tests. A remimazolam case met the WAO criterion with acute 11.6 falling to baseline 3.4 micrograms per L.
- The four hypersensitivity types differ in mechanism and timing: Type I (minutes, IgE), Type II (minutes to hours, cytotoxic IgG/IgM), Type III (hours to days, immune complex), Type IV (48 to 72 hours, cell-mediated T cells).
- The complement system's anaphylatoxins (C3a and C5a) directly trigger mast cell degranulation and vasodilation — the basis of complement-mediated transfusion reactions.
- The perioperative patient's immune system is suppressed by the stress response (cortisol, catecholamines) and by immunosuppressive drugs (steroids, transplant regimens) — this is one reason why postoperative infection rates rise.
Meet the patient
A 45-year-old woman is induced for a laparoscopic cholecystectomy. Three minutes after rocuronium her airway pressure doubles, her saturation falls, and her blood pressure collapses to 60 systolic. There is no rash — the drapes hide everything below the neck.[3]
The clock is already running. This is perioperative anaphylaxis until proven otherwise, and the first drug is adrenaline. Everything else — antihistamines, steroids, classification, tryptase — comes after the patient is alive.[3]
References6ShowHide
- [1]Trujillo-Ocampo A, et al. Human NKT10 cells are enriched in cord-derived invariant natural killer T cells and mediate immune-regulation in a xenogeneic graft-versus-host disease model Front Immunol, 2026.PMID 42358969
- [2]Shende S, Rathored J. Vitamin D as an Immuno-Endocrine Modulator: Discovering Its Role in Autoimmune Disorders and Host Defense Mechanisms J Clin Med, 2026.PMID 42355910
- [3]Takazawa T. Perioperative anaphylaxis in Japan: Epidemiology, diagnosis, and challenges Allergol Int, 2026.PMID 41455630
- [4]Jo Y, et al. Remimazolam-Induced Anaphylaxis After Spinal Anesthesia: A Case Report and Literature Review J Clin Med, 2026.PMID 42278971
- [5]Habib R, et al. Sugammadex-Associated Delayed Laryngeal and Upper Airway Edema: A Novel Adverse Effect J Investig Med High Impact Case Rep, 2026.PMID 42113672
- [6]Tanei R, Hasegawa Y. Revisiting Atopy: The IgE-Dependent Amplification Loop as a Forgotten Driver of Atopic Dermatitis Pathophysiology, 2026.PMID 42347026