Mechanisms of nonimmunological histamine and tryptase release from human cutaneous mast cells

Oral vancomycin induced flushing syndrome in a multiple myeloma patient: A case report and review of the literature

BACKGROUND

Patients with hematological malignancies are at high-risk of Clostridium difficile infection (CDI). Oral vancomycin is a first-line treatment for CDI. Vancomycin has been widely reported to induce flushing syndrome (also known as Red man syndrome), a well-known hypersensitivity reaction mostly occurs after intravenous administration. However, a few cases of flushing syndrome due to oral vancomycin have been reported.

METHODS

We reported a case of the 68-year-old male with Multiple Myeloma contracted suspected CDI during chemotherapy, oral vancomycin (125 mg po q6h) was initiated for CDI. Approximately 24 hours after receiving oral vancomycin, the patient developed vancomycin flushing syndrome with facial flushing and an erythematous rash on the abdomen and back, despite normal vancomycin duration and renal function (no obvious risk factors).

RESULTS

The patient was diagnosed with Oral vancomycin induced flushing syndrome. The symptoms resolved after withdrawal of vancomycin and 4 days of treatment with loratadine.

CONCLUSION

Oral vancomycin-induced flushing syndrome is a rare complication that can occur in patients with CDI despite the absence of obvious risk factors. The underlying mechanism of oral vacomycin-induced flushing syndrome may be direct activation of mast cells following mast cell degranulation and histamine release via the MRGPRX2 receptor. However, this is just speculation and there are insufficient data, particularly in vivo data, to draw any conclusions. For patients with risk factors such as gastrointestinal pathology and renal insufficiency, monitoring of vancomycin serum concentration, mast cell degranulation, histamine release, and MRGPRX2 levels is recommended to avoid vancomycin flushing Syndrome, and vancomycin can still be used under supervision.

Functional human skin explants as tools for assessing mast cell activation and inhibition

Mast cells are activated through a variety of different receptors to release preformed granules and mediators synthesized de novo. However, the physiology and function of mast cells are not fully understood. Traditional studies of mast cell activation in humans have utilized cultures of tissue-derived mast cells including CD34+ progenitor cells or well-characterized commercially available cell lines. One limitation of these methods is that mast cells are no longer in a natural state. Therefore, their applicability to human skin disorders may be limited. Human skin explant models have been utilized to investigate the short-term effects of cell mediators, drugs, and irritants on skin while avoiding the ethical concerns surrounding in vivo stimulation studies with non-approved agents. Nonetheless, few studies have utilized intact human tissue to study mast cell degranulation. This "Methods" paper describes the development and application of an intact skin explant model to study human mast cell activation. In this manuscript, we share our protocol for setting up ex vivo human skin explants and describe the results of stimulation experiments and techniques to minimize trauma-induced histamine release. Skin explants were generated using de-identified, full-thickness, non-diseased skin specimens from plastic and reconstructive surgeries. Results were reproducible and demonstrated FcɛRI- and MRGPRX2-induced mediator release which was inhibited with the use of a BTK inhibitor and QWF, respectively. Thus, this explant model provides a quick and accessible method of assessing human skin mast cell activation and inhibition.

Case Report: Isosulfan Blue-Related Anaphylaxis

Anaphylaxis is an acute multisystem syndrome typically resulting from the sudden release of mast cell and basophil-derived mediators into the circulatory system. Isosulfan blue dye is a rare, but known, mediator of anaphylaxis with an incidence between 0.16% and 2% of cases. We report two cases of anaphylaxis attributed to the use of isosulfan blue dye in the intraoperative setting. Both of the patients we report had grade 3 anaphylactic reactions requiring vasopressors to correct significant hypotension. Both patients required overnight monitoring in the intensive care unit with the second patient also requiring continued vasopressor support.

Pseudo-Allergies in the Emergency Department: A Common Misdiagnosis of Hypersensitivity Type 1 Allergic Reaction

Type-1 hypersensitivity reaction represents an acute IgE-mediated reaction that can cause life-threatening conditions, such as anaphylactic shock, angioedema, and airway obstruction. Other reactions that can mimic type-1 hypersensitivity reactions include IgE-independent mast cell degranulation, bradykinin-mediated reactions, leukotrienes-mediated reactions, and pseudo-allergies. We use the term pseudo-allergy in this article for histamine-mediated reactions that are mast cell-independent. We did not discuss pseudo-allergic reactions that are not acute or life-threatening, such as celiac disease, Heiner's syndrome, eosinophilic esophagitis, and food protein-induced enterocolitis in our article because the emergency department is not the primary location to diagnose or treat these reactions. Herein, we present some allergic-like reactions that can be life-threatening, such as scombroid food poisoning (SFP), bradykinin-induced angioedema, IgE-independent angioedema, opioid-induced angioedema, and non-steroidal anti-inflammatory drug (NSAID)-induced hypersensitivity and angioedema. These reactions may have different treatments based on their mechanism of reaction. Histamine-mediated reactions, such as SFP, histamine-mediated angioedema, and mast cell degranulation induced by NSAIDs, and opioids can be treated with antihistamines, epinephrine, and corticosteroids. Bradykinin-induced angioedema, including hereditary angioedema and acquired angioedema, can be treated with fresh frozen plasma. Hereditary angioedema can be treated with many FDA-approved targeted medications, such as plasma-derived C1-INH, plasma kallikrein inhibitor (Ecallantide), and selective bradykinin-2 receptor antagonist (Icatibant). However, these targeted agents are not well-studied enough to be used for acquired angioedema. It is crucial for emergency medicine physicians to be familiar with and predict these reactions to prevent misdiagnosis, be prepared to treat these life-threatening conditions appropriately without delay and eliminate patients' exposure to any unnecessary investigations or treatments.

Allergenic and Mas-Related G Protein-Coupled Receptor X2-Activating Properties of Drugs: Resolving the Two

Since the seminal description implicating occupation of the Mas-related G protein-coupled receptor X2 (MRGPRX2) in mast cell (MC) degranulation by drugs, many investigations have been undertaken into this potential new endotype of immediate drug hypersensitivity reaction. However, current evidence for this mechanism predominantly comes from (mutant) animal models or in vitro studies, and irrefutable clinical evidence in humans is still missing. Moreover, translation of these preclinical findings into clinical relevance in humans is difficult and should be critically interpreted. Starting from our clinical priorities and experience with flow-assisted functional analyses of basophils and cultured human MCs, the objectives of this rostrum are to identify some of these difficulties, emphasize the obstacles that might hamper translation from preclinical observations into the clinics, and highlight differences between IgE- and MRPGRX2-mediated reactions. Inevitably, as with any subject still beset by many questions, alternative interpretations, hypotheses, or explanations expressed here may not find universal acceptance. Nevertheless, we believe that for the time being, many questions remain unanswered. Finally, a theoretical mechanistic algorithm is proposed that might advance discrimination between MC degranulation from MRGPRX2 activation and cross-linking of membrane-bound drug-reactive IgE antibodies.

Hypersensitivity reactions to small molecule drugs

Drug hypersensitivity reactions induced by small molecule drugs encompass a broad spectrum of adverse drug reactions with heterogeneous clinical presentations and mechanisms. These reactions are classified into allergic drug hypersensitivity reactions and non-allergic drug hypersensitivity reactions. At present, the hapten theory, pharmacological interaction with immune receptors (p-i) concept, altered peptide repertoire model, and altered T-cell receptor (TCR) repertoire model have been proposed to explain how small molecule drugs or their metabolites induce allergic drug hypersensitivity reactions. Meanwhile, direct activation of mast cells, provoking the complement system, stimulating or inhibiting inflammatory reaction-related enzymes, accumulating bradykinin, and/or triggering vascular hyperpermeability are considered as the main factors causing non-allergic drug hypersensitivity reactions. To date, many investigations have been performed to explore the underlying mechanisms involved in drug hypersensitivity reactions and to search for predictive and preventive methods in both clinical and non-clinical trials. However, validated methods for predicting and diagnosing hypersensitivity reactions to small molecule drugs and deeper insight into the relevant underlying mechanisms are still limited.

Mas-Related G Protein–Coupled Receptor-X2 and Its Role in Non-immunoglobulin E–Mediated Drug Hypersensitivity

A diverse group of Food and Drug Administration-approved cationic drugs including antibiotics, neuromuscular blocking drugs, opioids, antidepressants, and radiocontrast media activate mast cells and cause hypersensitivity reactions by both an immunoglobulin E IgE-dependent and independent manner. The recent discovery that these drugs activate mast cells via the G protein-coupled receptor known as Mas-related GPCR-X2 (MRGPRX2) has represented a paradigm shift of how drug hypersensitivity reactions are viewed. This article provides an overview of the current status of the role of MRGPRX2 on non-IgE-mediated drug hypersensitivity. Potential risk factors and evaluation for suspected MRGPRX2-mediated drug reactions are also discussed.

Antibody or Anybody? Considering the Role of MRGPRX2 in Acute Drug-Induced Anaphylaxis and as a Therapeutic Target

Acute anaphylaxis to small molecule drugs is largely considered to be antibody-mediated with immunogloblin E (IgE) and mast cell activation being key. More recently, a role for drug-reactive immunoglobulin G (IgG) with neutrophil activation has also been suggested, at least in reactions to neuromuscular blocking agents (NMBAs). However, the mast cell receptor MRGPRX2 has also been highlighted as a possible triggering mechanism in acute anaphylaxis to many clinically used drugs. Significantly, MRGPRX2 activation is not dependent upon the presence of drug-recognising antibody. Given the reasonable assumption that MRGPRX2 is expressed in all individuals, the corollary of this is that in theory, anybody could respond detrimentally to triggering drugs (recently suggested to be around 20% of a drug-like compound library). But this clearly is not the case, as the incidence of acute drug-induced anaphylaxis is very low. In this mini-review we consider antibody-dependent and -independent mechanisms of mast cell activation by small molecule drugs with a focus on the MRGPRX2 pathway. Moreover, as a juxtaposition to these adverse drug actions, we consider how increased understanding of the role of MRGPRX2 in anaphylaxis is important for future drug development and can complement exploration of this receptor as a drug target in broader clinical settings.

Revisiting the role of MRGPRX2 on hypersensitivity reactions to neuromuscular blocking drugs

Anaphylaxis is caused by a variety of triggers including Food and Drug Administration (FDA)-approved antibiotics, contrast media and neuromuscular blocking drugs (NMBDs). Traditionally, drug-induced anaphylaxis was thought to result mainly from IgE-mediated histamine release from mast cells. Recently, a G protein-coupled receptor known as MRGPRX2 has been identified and shown to be highly expressed on human skin but not lung mast cells. The demonstration that many NMBDs induce degranulation in human mast cells via MRGPRX2 led to the idea that this receptor contributes to NMBD-induced hypersensitivity reactions. However, other studies have raised doubts regarding its role in drug-induced hypersensitivity. This review discusses the current status and controversy on MRGPRX2's role on NMBD-induced hypersensitivity.

Histamine 2 receptors in cardiovascular biology: A friend for the heart

Undermining new mediators involved in the development and progression of cardiovascular diseases (CVDs) is vital for better disease management. Existing studies implicate a crucial role for inflammation and inflammatory cells, particularly mast cells, in cardiac diseases. Interestingly, the mast cell mediator, histamine, and its receptors profoundly impact the pathophysiology of the heart, resulting in hypertension-induced cardiac hypertrophy and other cardiac anomalies. In this review, we provide a detailed description of mast cell activation, mediators, and histamine receptors, with a particular focus on histamine 2 receptors (H2Rs). Preclinical and clinical studies using histamine receptor antagonists report improvement in cardiac function. Insights into the precise function of histamine receptors will aid in developing novel therapies and pave the way for repurposing antihistamines for cardiovascular diseases.

Non-IgE-mediated anaphylaxis

Anaphylaxis is a rapidly evolving, acute, life-threatening reaction that occurs rapidly on contact with a trigger. Anaphylaxis is classically defined as an allergen-driven process that induces specific IgE and the activation of mast cells and basophils through the cross-linking of IgE receptors. However, it is clear that non-IgE-mediated pathways can induce symptoms indistinguishable from those of classic anaphylaxis, and their activation could explain the severity of IgE-mediated anaphylaxis. Indeed, mast cells and basophils can be activated by antibodies against IgE or their receptors, by molecules such as anaphylatoxins, or through G-coupled receptors. Some other allergens can induce antibodies of class IgG that can activate neutrophils to produce a molecule similar to histamine to induce anaphylaxis. Finally, some inflammatory mediators such as bradykinin or prostaglandin can also modulate mast cell and basophil activation as well as directly cause vasodilation and bronchoconstriction, resulting in anaphylaxis-like reactions.

Vancomycin concentrations during cardiopulmonary bypass in pediatric cardiac surgery: a prospective study

INTRODUCTION

Few data are available regarding intraoperative plasma concentrations of vancomycin administered as prophylaxis in pediatric cardiac surgery. The aims of this study were to investigate during pediatric cardiac surgery with cardiopulmonary bypass(CPB) the attainment of the area-under-the-curve of the vancomycin serum concentrations versus time over surgery to minimum inhibitory concentration ratio(AUC_intra/MIC) of 400 (mg × h)/l and/or a target concentration of 15-20 mg/l.

METHODS

In a prospective study, 40 patients divided into four subgroups (neonates, infants, children <10 years-old, ⩾10 years-old) undergoing cardiac surgery with cardiopulmonary bypass (CPB) were enrolled. A slow vancomycin bolus of 20 mg/kg, up to a maximum dose of 1000 mg was administered before skin incision and a further dose of 10 mg/kg (up to 500 mg) at CPB start. Vancomycin samples were collected intraoperatively at four time points.

RESULTS

The median (interquartile range) age was 241.5 days (47-3898) and the median weight was 7.1 kg (3.1-37). The median AUC_intra/MIC was 254.73 (165.89-508.06). In 11 patients the AUC_intra/MIC target was not reached. Neonates displayed the lowest AUC_intra/MIC values, and these were significantly lower than those of children ⩾10 years old (p = 0.02). Vancomycin concentrations were above the maximal target of 20 mg/l in 82.5% and 80% of patients at surgery and CPB start, respectively. At CPB and surgery end, 42.5% of patients showed vancomycin concentrations above 20 mg/l and 42.5% below 15 mg/l. Patients⩾10 years old showed the highest peak values whereas neonates were those with the lowest troughs. AUC_intra/MIC correlated with age(r:0.36, p = 0.02), weight(r:0.35, p = 0.03), intraoperative protein value(r:0.40, p = 0.01), CPB priming volume/kg(r:-0.33, p = 0.04), CPB duration(r:0.36, p = 0.02) and vancomycin troughs(r:0.35, p = 0.04).

CONCLUSIONS

An AUC_intra/MIC ⩾400 target was not reached in one-quarter of children undergoing heart surgery. Vancomycin peaked before the start of surgery and neonates were those with the lowest troughs. Vancomycin concentrations are affected by CPB hemodilution and by patients' age and weight.

Minireview: Mas-related G protein-coupled receptor X2 activation by therapeutic drugs

Symptoms that resemble allergic reactions, such as pruritus, flushing, and hypotension, are common side effects of therapeutic drugs. In a true allergic reaction, Immunoglobulin E (IgE) antibodies recognize the drug and trigger mediator release from mast cells through cross-linking of IgE receptors. However, many drugs can bypass this pathway and can activate mast cells directly through MRGPRX2, a G protein-coupled receptor that responds to a wide range of small molecules, peptides, and proteins that have little in common except for a net positive charge. This review will provide an overview of MRGPRX2, including its expression pattern, studies of its pharmacology, and its orthologs. It also will review evidence for MRGPRX2 activation by many drugs closely associated with these reactions.

A 2-year-old girl with periprocedural anaphylaxis

Periprocedural or perioperative anaphylaxis is rare, with an estimated incidence of 1 in 10,000 to 40,000 sedation cases. During such procedures, patients are often exposed to numerous medications, such as antimicrobials, neuromuscular blocking agents, sedative and/or hypnotics, and opioids. The most commonly implicated agents include antibiotics (in the United States) and neuromuscular blocking agents (in Europe). In this article, we explore the differential diagnosis and laboratory investigation of a case of periprocedural anaphylaxis.

Circulatory collapse during wound closure in spine surgery with an unknown cause: a possible adverse effect of topical application of vancomycin?

BACKGROUND

Vancomycin (VCM) is effective in fighting Gram-positive bacteria related severe infections, and topical application of VCM powder is widely used in orthopedic surgery to prevent wound infection. However, VCM could lead to infusion rate-dependent antibody-and complement-independent anaphylaxis reaction by inducing direct release of histamine.

CASE PRESENTATION

We retrospectively analyzed seven cases of severe hypotension and shock during wound closure or immediately after orthopedic surgery with unidentifiable reasons. We found that these cases were all associated with local application of VCM powder during wound closure process. Two patients experienced sudden cardiac arrest. Most of the cases (6/7) with circulatory collapse were discharged without severe sequelae. While one case with application of 3 g VCM developed cardiac arrest and remained in a coma due to hypoxic-hypoxic encephalopathy. The clinical presentations and the time of the shock onset were considered to be related with a VCM induced anaphylaxis reaction. However, as this was a retrospective study, and there was no laboratory examination performed, the conclusion was made upon differential diagnosis based on clinical manifestations and the timing of the shock.

CONCLUSIONS

Local application of VCM may not be as safe as was once believed and may lead to a related anaphylaxis. As VCM induced infusion-rate dependent, non-IgE mediated anaphylaxis is characterized by delayed occurrence, severe hypotension and even circulatory collapse, surgeons and anesthesiologists should be extra vigilant during and after VCM application.

Adverse reactions to vancomycin and cross-reactivity with other antibiotics

PURPOSE OF REVIEW

Glycopeptide antibiotics such as vancomycin are frequently utilized to treat resistant Gram-positive infections such as methicillin-resistant Staphylococcus aureus. The current literature on glycopeptide and lipoglycopeptide structure, hypersensitivity and potential cross-reactivity was reviewed, highlighting implications for safe prescribing.

RECENT FINDINGS

Structurally similar, glycopeptides could theoretically cross-react. Immediate reactions to vancomycin include non-IgE-mediated reactions (e.g. red man syndrome) and IgE-mediated hypersensitivity (e.g. anaphylaxis), sharing clinical features. Vancomycin can activate mast cells via MAS-related G-protein-coupled receptor X2, an IgE-independent receptor implicated in non-IgE reactions. In-vivo and in-vitro testing for suspected IgE-mediated reactions to glycopeptides remain ill-defined. Vancomycin is increasingly recognized to cause severe cutaneous adverse reactions (SCAR), with drug reaction with eosinophilia and systemic symptoms (DRESS) predominantly reported. Vancomycin DRESS has been associated with HLA-A32:-01, with a number needed to prevent of 1 in 74. Data demonstrating cross-reactivity amongst glycopeptides and lipoglycopeptides is limited to case reports/series.

SUMMARY

Further studies and in-vivo/in-vitro diagnostics are required for better differentiation between IgE and non-IgE glycopeptide reactions. Despite its association with vanomycin DRESS, utility of pharmacogenomic screening for HLA-A32: 01 is ill-defined. Although HLA-A32:01 has been associated with vancomycin DRESS, its utility for pharmacogenomic screening is ill defined. Further clinical and immunological cross-reactivity data for glycopeptide/lipoglycopeptide antibiotics is required.

An Updated Review of the Molecular Mechanisms in Drug Hypersensitivity

Drug hypersensitivity may manifest ranging from milder skin reactions (e.g., maculopapular exanthema and urticaria) to severe systemic reactions, such as anaphylaxis, drug reactions with eosinophilia and systemic symptoms (DRESS)/drug-induced hypersensitivity syndrome (DIHS), or Stevens–Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN). Current pharmacogenomic studies have made important strides in the prevention of some drug hypersensitivity through the identification of relevant genetic variants, particularly for genes encoding drug-metabolizing enzymes and human leukocyte antigens (HLAs). The associations identified by these studies are usually drug, phenotype, and ethnic specific. The drug presentation models that explain how small drug antigens might interact with HLA and T cell receptor (TCR) molecules in drug hypersensitivity include the hapten theory, the p-i concept, the altered peptide repertoire model, and the altered TCR repertoire model. The broad spectrum of clinical manifestations of drug hypersensitivity involving different drugs, as well as the various pathomechanisms involved, makes the diagnosis and management of it more challenging. This review highlights recent advances in our understanding of the predisposing factors, immune mechanisms, pathogenesis, diagnostic tools, and therapeutic approaches for drug hypersensitivity.

Effects of opioid and nonopioid analgesics on canine wheal formation and cultured human mast cell degranulation

Mast cell (MC) degranulation has been implicated in the side effect profile of a variety of clinically useful agents. Thus, after intrathecal delivery, formation of space-occupying, meningeally-derived masses may be related to local MC degranulation. We systematically characterized degranulating effects of opioid and nonopioid analgesics on cutaneous flares in the dog and in primary human MC (hMC) cultures.

METHODS

Dogs were anesthetized with IV propofol and received intradermal (ID) injections (50μL). Flare diameters were measured at 30min. Drugs showing flare responses were tested after intramuscular (IM) cromolyn (10mg/kg), a MC stabilizer. Human primary MCs (human cord blood CD34⁺/CD45⁺ cells) were employed and β-hexosaminidase in cell-free supernatants were measured to assess degranulation.

RESULTS

A significant skin flare for several classes of agents was observed including opioids, ziconotide, ketamine, ST-91, neostigmine, adenosine, bupivacaine, lidocaine, MK-801 and 48/80. Tizanidine, fentanyl, alfentanil, gabapentin and baclofen produced no flare. Flare produced by all ID agents, except adenosine, bupivacaine and lidocaine, was reduced by cromolyn. Naloxone had no effect upon opiate or 48/80 evoked flares. In hMC studies, 48/80 resulted in a concentration-dependent release of β-hexosaminidase. The rank order of drug-induced hMC β-hexosaminidase release was similar to that for flares.

CONCLUSIONS

A variety of therapeutically useful drugs degranulate MCs. This action may account for side effects such as the intrathecal granuloma resulting from spinally-delivered opioids. This degranulating effect may be useful in predicting potential intrathecal toxicity in the development of novel agents.

Management around invasive procedures in mastocytosis: An update

OBJECTIVE

Mastocytosis is a chronic hematologic disorder that is characterized by the accumulation of aberrant mast cells and typically involves the skin and/or bone marrow. Patients with mastocytosis are at increased risk of anaphylaxis. Based on theoretical assumptions, medical procedures requiring general anesthesia or radiocontrast media are deemed hazardous for patients with mastocytosis. The objective of this article is to provide a comprehensive overview of the actual risk of iatrogenic anaphylaxis and provide recommendations for daily practice.

DATA SOURCES

Various scientific search engines were used (eg, PubMed and Medline).

STUDY SELECTIONS

Because of the paucity of high-level studies on this topic, all available evidence was considered, including case reports.

RESULTS

Reliable data on the incidence of iatrogenic anaphylaxis in mastocytosis are lacking. However, although the incidence as reported in (retrospective) cohort studies is higher than in the general population, it is still lower than commonly anticipated, with an incidence of 5.4% in 1 study. Adequate premedication and avoidance of certain physical stimuli can further decrease this risk by 10-fold. The role of drugs as elicitors of anaphylaxis is perhaps overestimated, and physical stimuli are at least as important in inducing release of mast cell mediators.

CONCLUSION

This article provides practical recommendations for the management of invasive procedures in patients with mastocytosis based on current knowledge of this topic.

Emerging Roles for MAS-Related G Protein-Coupled Receptor-X2 in Host Defense Peptide, Opioid, and Neuropeptide-Mediated Inflammatory Reactions

Mast cells (MCs) are tissue-resident immune cells that contribute to host defense but are best known for their roles in allergic and inflammatory diseases. In humans, MCs are divided into two subtypes based on the protease content of their secretory granules. Thus, human lung MCs contain only tryptase and are known as MC_T, whereas skin MCs contain both tryptase and chymase and are known as MC_TC. Patients with severe asthma display elevated MCs in the lung, which undergo phenotypic change from MC_T to MC_TC. Although the human genome contains four Mas related G protein coupled receptor X (MRGPRX) genes, an important feature of MC_TC is that they selectively express MRGPRX2. It is activated by antimicrobial host defense peptides such as human β-defensins and the cathelicidin LL-37 and likely contributes to host defense. MRGPRX2 is also a receptor for the neuropeptide substance P, major basic protein, eosinophil peroxidase, opioids, and many FDA-approved cationic drugs. Increased expression of MRGPRX2 or enhanced downstream signaling likely contributes to chronic inflammatory diseases such as rosacea, atopic dermatitis, chronic urticaria, and severe asthma. In this chapter, I will discuss the expression profile and function of MRGPRX1-4 and review the emerging roles of MRGPRX2 on host defense, chronic inflammatory diseases, and drug-induced pseudoallergic reactions. I will also examine the novel aspects of MRGPRX2 signaling in MCs as it related to degranulation and review the mechanisms of its regulation.

Precision medicine in allergic disease-food allergy, drug allergy, and anaphylaxis-PRACTALL document of the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma and Immunology

This consensus document summarizes the current knowledge on the potential for precision medicine in food allergy, drug allergy, and anaphylaxis under the auspices of the PRACTALL collaboration platform. PRACTALL is a joint effort of the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma and Immunology, which aims to synchronize the European and American approaches to allergy care. Precision medicine is an emerging approach for disease treatment based on disease endotypes, which are phenotypic subclasses associated with specific mechanisms underlying the disease. Although significant progress has been made in defining endotypes for asthma, definitions of endotypes for food and drug allergy or for anaphylaxis lag behind. Progress has been made in discovery of biomarkers to guide a precision medicine approach to treatment of food and drug allergy, but further validation and quantification of these biomarkers are needed to allow their translation into practice in the clinical management of allergic disease.

Reclassifying Anaphylaxis to Neuromuscular Blocking Agents Based on the Presumed Patho-Mechanism: IgE-Mediated, Pharmacological Adverse Reaction or "Innate Hypersensitivity"?

Approximately 60% of perioperative anaphylactic reactions are thought to be immunoglobulin IgE mediated, whereas 40% are thought to be non-IgE mediated hypersensitivity reactions (both considered non-dose-related type B adverse drug reactions). In both cases, symptoms are elicited by mast cell degranulation. Also, pharmacological reactions to drugs (type A, dose-related) may sometimes mimic symptoms triggered by mast cell degranulation. In case of hypotension, bronchospasm, or urticarial rash due to mast cell degranulation, identification of the responsible mechanism is complicated. However, determination of the type of the underlying adverse drug reaction is of paramount interest for the decision of whether the culprit drug may be re-administered. Neuromuscular blocking agents (NMBA) are among the most frequent cause of perioperative anaphylaxis. Recently, it has been shown that NMBA may activate mast cells independently from IgE antibodies via the human Mas-related G-protein-coupled receptor member X2 (MRGPRX2). In light of this new insight into the patho-mechanism of pseudo-allergic adverse drug reactions, in which as drug-receptor interaction results in anaphylaxis like symptoms, we critically reviewed the literature on NMBA-induced perioperative anaphylaxis. We challenge the dogma that NMBA mainly cause IgE-mediated anaphylaxis via an IgE-mediated mechanism, which is based on studies that consider positive skin test to be specific for IgE-mediated hypersensitivity. Finally, we discuss the question whether MRGPRX2 mediated pseudo-allergic reactions should be re-classified as type A adverse reactions.

In Vivo Cysteinyl Leukotriene Release in Allergic and Nonallergic Immediate Hypersensitivity Reactions during Anesthesia

BACKGROUND

Immediate hypersensitivity reactions occurring during anesthesia are classified as allergic when skin tests and mast cell tryptase are positive and as nonallergic when negative results are obtained. Cysteinyl leukotrienes (cysLTs) are potent mediators synthesized by mast cell and eosinophil that induce bronchial constriction. They could play a role in hypersensitivity reactions.

METHODS

cysLT C4, D4, and E4 concentrations were measured by a competition immunoassay in serial plasma samples obtained prospectively from 21 anesthetized controls and retrospectively from 34 patients who reacted at induction of anesthesia (24 with allergic and 10 with nonallergic reactions).

RESULTS

In controls, the median (interquartile range) cysLT concentration was 0.83 (0.69 to 1.02) μg/l before anesthesia and was unchanged 30 min, 6 h, and 24 h afterward. In the patients with allergic reactions, the values were highly increased 30 to 60 min after the reaction (17.9 [7.8 to 36.0] μg/l), while the patients with nonallergic reactions had less increased values (7.3 [3.0 to 11.5] μg/l). The difference between the three groups was significant (P < 0.0001). Increased values persisted during the 24 h of observation. Concentrations were significantly higher in patients with bronchospasm (P = 0.016).

CONCLUSIONS

cysLTs appear to be an important mediator of allergic and nonallergic immediate hypersensitivity reactions. These findings might open a new field for management of patients with hypersensitivity reactions, especially nonallergic ones.

Current Knowledge and Management of Hypersensitivity to Perioperative Drugs and Radiocontrast Media

Perioperative anaphylaxis is an iatrogenic clinical condition, most often after anesthetic induction. Several mechanisms are implicated, including IgE- and non-IgE-mediated mechanisms. Perioperative anaphylaxis tends to be severe and has a higher mortality rate than anaphylaxis in other settings. This is partly due to factors that impair early recognition of anaphylaxis. Neuromuscular blocking agents, latex containing products, and antibiotics are the most common etiology. Chlorhexidine and dyes are increasingly culprits. The newest emerging cause is sugammadex, which is used for reversal of the effects of steroidal neuromusclar agents, such as rocuronium. Latex-induced allergy is becoming less common than in the 1980s due to primary and secondary prevention measures. Serum tryptase levels during the time of anaphylaxis and skin testing to suspected agents as an outpatient are necessary to confirm the diagnosis. Management includes epinephrine and aggressive fluid therapy. With radiocontrast media allergy, patients with a history of immediate hypersensitivity reactions to radiocontrast media should receive steroid and antihistamine premedication before re-exposure. Because IgE-mediated anaphylaxis to radiocontrast media is rare, there is a universal consensus that routinely skin testing all patients with a past reaction is not effective.

Emerging concepts: mast cell involvement in allergic diseases

In a process known as overt degranulation, mast cells can release all at once a diverse array of products that are preformed and present within cytoplasmic granules. This occurs typically within seconds of stimulation by environmental factors and allergens. These potent, preformed mediators (ie, histamine, heparin, serotonin, and serine proteases) are responsible for the acute symptoms experienced in allergic conditions such as allergic conjunctivitis, allergic rhinitis, allergy-induced asthma, urticaria, and anaphylaxis. Yet, there is reason to believe that the actions of mast cells are important when they are not degranulating. Mast cells release preformed mediators and inflammatory cytokines for periods after degranulation and even without degranulating at all. Mast cells are consistently seen at sites of chronic inflammation, including nonallergic inflammation, where they have the ability to temper inflammatory processes and shape tissue morphology. Mast cells can trigger actions and chemotaxis in other important immune cells (eg, eosinophils and the newly discovered type 2 innate lymphocytes) that then make their own contributions to inflammation and disease. In this review, we will discuss the many known and theorized contributions of mast cells to allergic diseases, focusing on several prototypical allergic respiratory and skin conditions: asthma, chronic rhinosinusitis, aspirin-exacerbated respiratory disease, allergic conjunctivitis, atopic dermatitis, and some of the more common medication hypersensitivity reactions. We discuss traditionally accepted roles that mast cells play in the pathogenesis of each of these conditions, but we also delve into new areas of discovery and research that challenge traditionally accepted paradigms.

Human IgE-independent systemic anaphylaxis

Anaphylaxis is a rapidly developing, life-threatening, generalized or systemic allergic reaction that is classically elicited by antigen crosslinking of antigen-specific IgE bound to the high-affinity IgE receptor FcεRI on mast cells and basophils. This initiates signals that induce cellular degranulation with release and secretion of vasoactive mediators, enzymes, and cytokines. However, IgE-independent mechanisms of anaphylaxis have been clearly demonstrated in experimental animals. These include IgG-dependent anaphylaxis, which involves the triggering of mediator release by IgG/antigen complex crosslinking of FcγRs on macrophages, basophils, and neutrophils; anaphylaxis mediated by binding of the complement-derived peptides C3a and C5a to their receptors on mast cells, basophils, and other myeloid cells; and direct activation of mast cells by drugs that interact with receptors on these cells. Here we review the mechanisms involved in these IgE-independent forms of anaphylaxis and the clinical evidence for their human relevance. We conclude that this evidence supports the existence of all 3 IgE-independent mechanisms as important causes of human disease, although practical and ethical considerations preclude their demonstration to the degree of certainty possible with animal models. Furthermore, we cite evidence that different clinical situations can suggest different mechanisms as having a primal role in anaphylaxis and that IgE-dependent and distinct IgE-independent mechanisms can act together to increase anaphylaxis severity. As specific agents become available that can interfere with mechanisms involved in the different types of anaphylaxis, recognition of specific types of anaphylaxis is likely to become important for optimal prophylaxis and therapy.

Report from the National Institute of Allergy and Infectious Diseases workshop on drug allergy

Allergic reactions to drugs are a serious public health concern. In 2013, the Division of Allergy, Immunology, and Transplantation of the National Institute of Allergy and Infectious Diseases sponsored a workshop on drug allergy. International experts in the field of drug allergy with backgrounds in allergy, immunology, infectious diseases, dermatology, clinical pharmacology, and pharmacogenomics discussed the current state of drug allergy research. These experts were joined by representatives from several National Institutes of Health institutes and the US Food and Drug Administration. The participants identified important advances that make new research directions feasible and made suggestions for research priorities and for development of infrastructure to advance our knowledge of the mechanisms, diagnosis, management, and prevention of drug allergy. The workshop summary and recommendations are presented herein.

Morphine stimulates cancer progression and mast cell activation and impairs survival in transgenic mice with breast cancer

BACKGROUND

Morphine stimulates angiogenesis and cancer progression in mice. We investigated whether morphine influences tumour onset, development, and animal model survival, and whether µ-opioid receptor (MOR), lymphangiogenesis, mast cell activation, and substance P (SP) are associated with the tumour-promoting effects of morphine.

METHODS

Transgenic mice with a rat C3(1) simian virus 40 large tumour antigen fusion gene which demonstrate the developmental spectrum of human infiltrating ductal breast carcinoma were used. Mice were treated at different ages with clinically relevant doses of morphine or phosphate-buffered saline to determine the effect on tumour development and progression, and on mouse survival. Tumours were analysed for MOR, angiogenesis, lymphangiogenesis, SP, and mast cell activation by immunofluorescent- or laser scanning confocal-microscopy. Cytokine and SP levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Morphine did not influence tumour development when given before the onset of tumour appearance, but significantly promoted progression of established tumours, and reduced survival. MOR-immunoreactivity (ir) was observed in larger but not in smaller tumours. Morphine treatment resulted in increased tumour angiogenesis, peri-tumoural lymphangiogenesis, mast cell activation, and higher levels of cytokines and SP in tumours. SP-ir co-localized with mast cells and elsewhere in the tumours.

CONCLUSIONS

Morphine does not affect the onset of tumour development, but it promotes growth of existing tumours, and reduces overall survival in mice. MOR may be associated with morphine-induced cancer progression, resulting in shorter survival. Mast cell activation by morphine may contribute to increased cytokine and SP levels, leading to cancer progression and refractory pain.

Risk of anaphylaxis in opioid dependent persons: effects of heroin versus substitution substance

Background

Across Europe, illicit drug-related mortality has not declined despite ever increasing prevention measures. The cause of these deaths has traditionally been associated with overdose. Previous findings have revealed the appearance of non-lethal opioid concentrations, leading us to investigate a further cause of death. The symptoms of heroin intoxication with asphyxia and/or cardiovascular involvement resemble anaphylaxis, and therefore it has been speculated that such deaths might be caused by an allergic reaction. The study´s aims were to investigate levels of allergic mediators in long-term injecting drug users (IDU) compared to healthy controls and to determine if oral opioid substitution therapy (OST) resulted in similar allergic symptoms to those reported by IDU after intravenous (IV) heroin use.

Methods

We quantified the concentrations of histamine, diamine oxidase (DAO), tryptase and lipoprotein-associated phospholipase A₂ (LpPLA₂) at baseline and 1 h after administration of Substitol®retard (482 ± 220 mg) in 56 patients at a withdrawal centre (Austria) and compared them with healthy controls (n = 103). Questionnaires and face-to-face interviews were used to assess allergic symptoms and side effects in IDU. Descriptive statistical analyses of quantitative data were performed by using SPSS.

Results

Baseline histamine, tryptase and LpPLA₂ were significantly elevated in IDU compared to the healthy control group, while DAO decreased. Blood levels showed no significant change after oral substitution uptake. Self-reported allergic symptoms and side effects after IV heroin use were reported in 55 cases (98.2%), minimal symptoms were documented after OST (12.5%, 7/56).

Conclusions

This study revealed that baseline histamine concentrations were elevated in chronic IDU, although only relatively small changes in tryptase plasma levels occurred. After IV heroin application the reported allergic symptoms were mostly mild and did not lead to clinically relevant side effects. The substitution substance was clearly better tolerated than IV administered heroin. Elevated levels of allergic mediators such as histamine in IDUs may place them at greater risk of severe or fatal anaphylaxis when exposed to heroin; however, this requires further investigation.

The safety of codeine in patients with non-steroidal anti-inflammatory drug hypersensitivity: a preliminary study

BACKGROUND

Drug provocation testing should be performed before safely prescribing an analgesic for patients that are hypersensitive to non-steroidal anti-inflammatory drugs (NSAIDs). Whether or not the direct histamine releasing effect of codeine renders it useful in NSAID-hypersensitive patients is unknown. This study aimed to determine if codeine could be recommended as a safe treatment option for NSAID-hypersensitive patients without the need for oral drug provocation testing.

METHODS

The study included NSAID-hypersensitive patients with and without concurrent asthma, rhinitis, and chronic urticaria that presented to the allergy clinic between 1 January 1991 and 31 December 2010. Patient data were collected from the allergy clinic computer database. Patients challenged with codeine were included in the codeine group. The non-codeine group included those patients that were tested with analgesics other than codeine.

RESULTS

In total, data for 1071 patients, of whom 301 were in the codeine group, were analysed. The reaction rate to codeine was 7.3% and when compared in pairs, the rate was significantly lower than to meloxicam and nimesulide (odds ratios=0.26-0.31, respectively). The reaction rate to codeine did not differ from that to benzydamine, rofecoxib, and paracetamol. Symptomatic dermographism was associated (p=0.009) with test positivity to any drug.

CONCLUSIONS

Although, codeine was among the safest alternative drugs and none of the patients had an anaphylactic reaction to it, thus a challenge with codeine may be considered especially in patients with dermographism. The results of this preliminary study should be confirmed in a prospective study including a control group.

Anaphylaxis on reperfusion during liver transplantation with coagulopathy

We present a case in which anaphylaxis on hepatic reperfusion during liver transplantation presented only with hypotension and coagulopathy. There were no cutaneous manifestations or clinical features distinguishing anaphylaxis from postreperfusion syndrome. The recipient regularly consumed seafood, and the organ donor died of anaphylaxis to shellfish. The trigger for anaphylaxis was postulated to be passive transfer of immunoglobulin to the recipient. Anesthesiologists should be notified of donor factors to anticipate anaphylaxis. In this report, we discuss coagulopathy of anaphylaxis and contrast it with disseminated intravascular coagulation.

Histamine-releasing and allergenic properties of opioid analgesic drugs: resolving the two

Opioid analgesics are amongst the most commonly administered drugs in hospitals. Whether natural or synthetic, they show some common structural features, morphine-like pharmacological action and binding specificity for complementary opioid receptors. Tramadol differs from the other opioid analgesics in possessing monoaminergic activity in addition to its affinity for the µ opioid receptor. Many opioids are potent histamine releasers producing a variety of haemodynamic changes and anaphylactoid reactions, but the relationship of the appearance of these effects to the histamine plasma concentration is complex and there is no direct and invariable relationship between the two. Studies of the histamine-releasing effects, chiefly centred on morphine, reveal variable findings and conclusions often due to a range of factors including differences in technical measurements, dose, mode of administration, site of injection, the anatomical distribution of histamine receptors and heterogeneity of patient responses. Morphine itself has multiple direct effects on the vasculature and other haemodynamically-active mediators released along with histamine contribute to the variable responses to opioid drug administration. Despite their heavy use and occasional apparent anaphylactic-like side-effects, immunoglobulin E antibody-mediated immediate hypersensitivity reactions to the drugs are not often encountered. Uncertainties associated with skin testing with these known histamine-releasers, and the general unavailability of opioid drug-specific immunoglobulin E antibody tests contribute to the frequent failure to adequately investigate and establish underlying mechanisms of reactions by distinguishing anaphylactoid from true anaphylactic reactions. Clinical implications for diagnosis of reactions and some speculations on the rarity of true Type 1 allergies to these drugs are presented.

Determination of histamine in microdialysis samples from Guinea pig skin by high-performance liquid chromatography with fluorescence detection

AIM

To develop a sensitive and selective liquid-chromatographic method for the determination of histamine in microdialysis samples from guinea pig skin following allergenic provocation.

METHODS

The novel fluorescence derivatization method is based on an intramolecular excimer-forming reaction between 2 amino moieties of histamine and 2 molecules of 4-(1-pyrene)butanoyl chloride (PBC) yielding the corresponding dipyrene-labeled derivative.

RESULTS

The PBC derivative of histamine was separated within 20 min, and the detection limit (signal-to-noise ratio = 3) of histamine was 0.6 fmol/20 μl volume injected. The basal extracellular levels of histamine in guinea pig skin microdialysates were 20.6 ± 1.7 fmol/10 μl. Subcutaneous administration of histamine liberator compound 48/80 (3 mg/kg) increased the extracellular histamine levels in the skin dialysates by about 860%, whereas ovalbumin challenge (2 mg/kg i.v.) in the sensitized guinea pigs increased the extracellular histamine levels by about 3,030%.

CONCLUSION

The novel technique for histamine determination in microdialysis samples from the guinea pig skin may be utilized in preclinical research of antihistaminergic drugs and evaluation of allergenic properties of various dermal preparations such as transdermal drug delivery systems.

Degarelix, a novel GnRH antagonist, causes minimal histamine release compared with cetrorelix, abarelix and ganirelix in an ex vivo model of human skin samples

AIMS

Early studies on gonadotrophin-releasing hormone (GnRH) antagonists pointed out histamine-mediated anaphylactic reactions as a potential adverse effect of these drug candidates. In this study we have compared the histamine-releasing potential of four approved and marketed antagonists, degarelix, cetrorelix, abarelix and ganirelix in an ex vivo model of human skin samples.

METHODS

Human skin samples were obtained during cosmetic plastic surgery and kept in oxygenated saline solution. The samples were incubated either without or at different concentrations of the antagonists (3, 30 or 300 µg ml(-1) for all, except for ganirelix 1, 10 or 100 µg ml(-1) ). The drug-induced effect was expressed as the increase relative to basal release. The histamine-releasing capacity of the skin was verified by a universal histamine releaser, compound 40/80.

RESULTS

Degarelix had no significant effect on basal histamine release in the 3 to 300 µg ml(-1) concentration range. The effect of ganirelix was moderate causing a nonsignificant increase of 81 ± 27% at the 100 µg ml(-1) concentration. At 30 and 300 µg ml(-1) concentrations abarelix (143 ± 29% and 362 ± 58%, respectively, P < 0.05) and cetrorelix (228 ± 111% and 279 ± 46%, respectively, P < 0.05) caused significantly increased histamine release.

CONCLUSIONS

In this ex vivo human skin model, degarelix displayed the lowest capacity to release histamine followed by ganirelix, abarelix and cetrorelix. These findings may provide indirect hints as to the relative likelihood of systemic anaphylactic reactions in clinical settings.

Silver nanoparticle-induced degranulation observed with quantitative phase microscopy

Monitoring a degranulation process in a live mast cell is a quite important issue in immunology and pharmacology. Because the size of a granule is normally much smaller than the resolution limit of an optical microscope system, there is no direct real-time live cell imaging technique for observing degranulation processes except for fluorescence imaging techniques. In this research, we propose optical quantitative phase microscopy (QPM) as a new observation tool to study degranulation processes in a live mast cell without any fluorescence labeling. We measure the cell volumes and the cross sectional profiles (x-z plane) of an RBL-2H3 cell and a HeLa cell, before and after they are exposed to calcium ionophore A23187 and silver nanoparticles (AgNPs). We verify that the volume and the cross sectional line profile of the RBL-2H3 cell were changed significantly when it was exposed to A23187. When 50 microg/mL of AgNP is used instead of A23187, the measurements of cell volume and cross sectional profiles indicate that RBL-2H3 cells also follow degranulation processes. Degranulation processes for these cells are verified by monitoring the increase of intracellular calcium ([Ca(2+)](i)) and histamine with fluorescent methods.

The investigation of bronchospasm during induction of anaesthesia

BACKGROUND

The aim of this study was to ascertain whether anaesthetic induction-related anaphylactic bronchospasm could be distinguished from other types of bronchospasm by clinical features and response to treatment. Such features could then be used to identify a group of patients in whom skin testing is indicated.

METHODS

We retrospectively studied data from 183 patients referred to an anaesthetic allergy clinic because of bronchospasm during induction. For the analysis, the patients were divided into two groups depending on whether there was evidence suggesting immunological anaphylaxis.

RESULTS

When the patients in whom intradermal tests were positive were compared with those in whom intradermal tests were negative, the skin test-positive patients had significantly more severe reactions, and they were more commonly associated with other clinical signs. Mast cell tryptase (MCT) was an excellent discriminator between reactions likely to be allergic and those unlikely to be allergic.

CONCLUSIONS

Anaphylactic bronchospasm related to induction of anaesthesia is more likely to be severe than bronchospasm due to non-immune causes. An allergic cause is more likely if there are associated features of anaphylaxis (skin changes, hypotension, angioedema) or elevated MCT. Patients with any of these features should undergo immuno-allergolical investigation.

Cytosolic PLA2 is required for CTL-mediated immunopathology of celiac disease via NKG2D and IL-15

IL-15 and NKG2D promote autoimmunity and celiac disease by arming cytotoxic T lymphocytes (CTLs) to cause tissue destruction. However, the downstream signaling events underlying these functional properties remain unclear. Here, we identify cytosolic phospholipase A₂ (cPLA₂) as a central molecule in NKG2D-mediated cytolysis in CTLs. Furthermore, we report that NKG2D induces, upon recognition of MIC⁺ target cells, the release of arachidonic acid (AA) by CTLs to promote tissue inflammation in association with target killing. Interestingly, IL-15, which licenses NKG2D-mediated lymphokine killer activity in CTLs, cooperates with NKG2D to induce cPLA₂ activation and AA release. Finally, cPLA₂ activation in intraepithelial CTLs of celiac patients provides an in vivo pathophysiological dimension to cPLA₂ activation in CTLs. These results reveal an unrecognized link between NKG2D and tissue inflammation, which may underlie the emerging role of NKG2D in various immunopathological conditions and define new therapeutic targets.

Forensic Lung Pathology

Sudden and unexpected natural deaths and nonnatural deaths may result from various pulmonary conditions. Additionally, several nonpulmonary conditions of forensic significance may be complicated by the development of respiratory lesions. Certain situations with pulmonary pathology are particularly likely to be critically scrutinized and may form the basis of allegations of medical negligence, other personal injury liability, or wrongful death.1