Possible circadian variation of serum mast cell tryptase concentration

Short-term biological variation of serum tryptase

OBJECTIVES

Serum tryptase is a biomarker of mast cell activation. Among others, it is used in the diagnosis of anaphylaxis where a significant increase during the acute phase supports the diagnosis. When evaluating changes in biomarker levels, it is of utmost importance to consider the biological variation of the marker. Therefore, the aim of this study was to evaluate the short-term biological variation of serum tryptase.

METHODS

Blood samples were drawn at 9 AM three days in a row from apparently healthy subjects. On day two, additional blood samples were drawn every third hour for 12 h. The tryptase concentration was measured in serum using a fluoroenzyme immunoassay (ImmunoCAP™, Thermo Fisher Scientific). Linear mixed-effects models were used to calculate components of biological variation.

RESULTS

In 32 subjects, the overall mean concentration of tryptase was 4.0 ng/mL (range, 1.3-8.0 ng/mL). The within-subject variation was 3.7 % (95 % confidence interval (CI) 3.0-4.4 %), the between-subject variation was 31.5 % (95 % CI 23.1-39.8 %), and the analytical variation was 3.4 % (95 % CI 2.9-4.1 %). The reference change value was 13.3 % for an increase in tryptase at a 95 % level of significance. No significant day-to-day variation was observed (p=0.77), while a minute decrease in the serum concentration was observed during the day (p<0.0001).

CONCLUSIONS

Serum tryptase is a tightly regulated biomarker with very low within-subject variation, no significant day-to-day variation, and only minor semidiurnal variation. In contrast, a considerable between-subject variation exists. This establishes serum tryptase as a well-suited biomarker for monitoring.

Unravelling the pathophysiology of chronic kidney disease-associated pruritus

For decades, itch related to chronic kidney disease (CKDaP) has been a clinical problem, but the aetiology and pathophysiology of CKDaP are still not yet fully understood—currently the underlying pathophysiological mechanisms are thought to be multifactorial. As new therapeutic targets have recently been identified and clinical trials have shown promising results, our current understanding of the interrelationships has expanded significantly. Here we review the pathophysiology and recent findings on modulation and sensitization of itch contributing to the development of CKDaP, covering hypothesis regarding immune system dysfunction, metabolic changes, uremic toxin deposition, peripheral neuropathy and imbalances in the endogenous opioid system.

Diurnal Variations in Skin Prick Testing

Background: Prior research suggests that skin prick testing (SPT) might be larger in the afternoon, with unclear clinical significance. Methods: This retrospective chart review analyzed SPT results from patients between June 2008 and June 2017, organized into 4 time groups for analysis (Group 1: 7:00 AM -10:29 AM, Group 2: 10:30 AM -11:59 AM, Group 3: 12:00 PM -2:29 PM, and Group 4: 2:30 PM -8:15 PM). Results: In total, 12,982 (n) patient test results had positive histamine and were included in final analysis. Histamine wheal size was not significantly increased in the PM compared with AM (P = 0.89). Food allergen and aeroallergen wheal sizes were not significantly increased in PM. Histamine erythema size was increased in the PM compared with AM (P ≤ 0.01). Food allergen and aeroallergen erythema sizes trended toward an increase in the PM. Conclusions: There were not significant differences in SPT wheal size based on time of day for histamine, food allergens, or aeroallergens. SPT can be reliably performed at any time of day.

Correlation of Nasal Fluid Biomarkers and Symptoms in Patients with Persistent Allergic Rhinitis

OBJECTIVES

This study investigated whether the biomarkers present in nasal fluid reflect the severity of symptoms in patients with persistent allergic rhinitis (PAR).

METHODS

We enrolled 29 PAR patients complaining of nasal symptoms and testing positive to skin prick test. Patients' total nasal symptom score (TNSS) was measured and their nasal lavage fluid (NALF) was collected. The levels of biomarkers including Clara cell protein 16 (CC16), tryptase, and interleukin 5 (IL-5) in NALF were determined via enzyme-linked immunosorbent assay (ELISA).

RESULTS

PAR patients were classified into persistent mild and persistent moderate-to-severe groups according to the Allergic Rhinitis and its Impact on Asthma (ARIA) guidelines. The CC16 alone was significantly negatively correlated with TNSS (P < .05). Further, the CC16 level was significantly lower in persistent moderate-to-severe group than persistent mild group of patients (P < .05).

CONCLUSIONS

The levels of CC16 alone among several NALF biomarkers showed an inverse correlation with symptoms of PAR patients.

The Circadian Clock Drives Mast Cell Functions in Allergic Reactions

Allergic diseases are known to vary in the severity of their symptoms throughout the day/night cycle. This rhythmicity is also observed in mast cell function and responsiveness. Mast cells are key effector cells of allergic reactions and release cytokines, chemokines, and important inflammatory mediators such as histamine, which have been shown to display diurnal variation. Recent research clarified that mast cells are controlled by their internal clock-which is regulated by a specific set of clock genes-as well as external factors such as light sensed by the suprachiasmatic nuclei, hormonal status, or diet. Here, we give an overview of the connections between circadian clock, mast cells, and allergic disease. Further work aimed at studying the role of chronotherapy/chronomedicine should take into account this rhythmic nature of not only mast cells but also the immune responses generated by mast cell signaling.

Allergen-specific basophil reactivity exhibits daily variations in seasonal allergic rhinitis

It remains poorly understood how symptoms in allergic rhinitis are most severe during overnight or early in the morning. The circadian clock consisting of a network of several ‘clock genes’ including Clock drives daily rhythms in physiology. This study showed that allergen-induced surface CD203c expression on basophils in seasonal allergic rhinitis caused by Japanese cedar pollen exhibited a time-of-day-dependent variation associated with temporal variations in canonical circadian clock gene expression. We also found that bone-marrow-derived basophils (BM basophils) generated from wild-type mice exhibited a time-of-day-dependent variation in IgE-mediated IL-4 and histamine production, which was not observed in BM basophils generated from Clock-mutated mice. Therefore, allergen-specific basophil reactivity shows daily variations depending on the circadian clock activity in basophils, which could partly explain temporal symptomatic variations in allergic rhinitis. Additionally, circadian variations in CD203c expression should be considered for interpretation of this biomarker in clinical research.

IgE-dependent activation of human mast cells and fMLP-mediated activation of human eosinophils is controlled by the circadian clock

Symptoms of allergic attacks frequently exhibit diurnal variations. Accordingly, we could recently demonstrate that mast cells and eosinophils - known as major effector cells of allergic diseases - showed an intact circadian clock. Here, we analyzed the role of the circadian clock in the functionality of mast cells and eosinophils. Human intestinal mast cells (hiMC) were isolated from intestinal mucosa; human eosinophils were isolated from peripheral blood. HiMC and eosinophils were synchronized by dexamethasone before stimulation every 4h around the circadian cycle by FcɛRI crosslinking or fMLP, respectively. Signaling molecule activation was examined using Western blot, mRNA expression by real-time RT-PCR, and mediator release by multiplex analysis. CXCL8 and CCL2 were expressed and released in a circadian manner by both hiMC and eosinophils in response to activation. Moreover, phosphorylation of ERK1/2, known to be involved in activation of hiMC and eosinophils, showed circadian rhythms in both cell types. Interestingly, all clock genes hPer1, hPer2, hCry1, hBmal1, and hClock were expressed in a similar circadian pattern in activated and unstimulated cells indicating that the local clock controls hiMC and eosinophils and subsequently allergic reactions but not vice versa.

The circadian clock is functional in eosinophils and mast cells

Allergic diseases are frequently exacerbated between midnight and early morning, suggesting a role for the biological clock. Mast cells (MC) and eosinophils are the main effector cells of allergic diseases and some MC-specific or eosinophil-specific markers, such as tryptase or eosinophil cationic protein, exhibit circadian variation. Here, we analysed whether the circadian clock is functional in mouse and human eosinophils and MC. Mouse jejunal MC and polymorphonuclear cells from peripheral blood (PMNC) were isolated around the circadian cycle. Human eosinophils were purified from peripheral blood of non-allergic and allergic subjects. Human MC were purified from intestinal tissue. We found a rhythmic expression of the clock genes mPer1, mPer2, mClock and mBmal1 and eosinophil-specific genes mEcp, mEpo and mMbp in murine PMNC. We also found circadian variations for hPer1, hPer2, hBmal1, hClock, hEdn and hEcp mRNA and eosinophil cationic protein (ECP) in human eosinophils of both healthy and allergic people. Clock genes mPer1, mPer2, mClock and mBmal1 and MC-specific genes mMcpt-5, mMcpt-7, mc-kit and mFcεRI α-chain and protein levels of mMCPT5 and mc-Kit showed robust oscillation in mouse jejunum. Human intestinal MC expressed hPer1, hPer2 and hBmal1 as well as hTryptase and hFcεRI α-chain, in a circadian manner. We found that pre-stored histamine and de novo synthesized cysteinyl leukotrienes, were released in a circadian manner by MC following IgE-mediated activation. In summary, the biological clock controls MC and eosinophils leading to circadian expression and release of their mediators and, hence it might be involved in the pathophysiology of allergy.

An increase in serum tryptase even below 11.4 ng/mL may indicate a mast cell-mediated hypersensitivity reaction: a prospective study in Hymenoptera venom allergic patients

BACKGROUND

During a systemic hypersensitivity reaction (SR), an increase in serum tryptase compared to the baseline value is an indicator of mast cell activation, most often due to an IgE-mediated mechanism.

OBJECTIVE

To study the relevance of an increase in serum tryptase below the upper normal value of 11.4 ng/mL.

METHODS

Serum tryptase levels were measured in 35 patients with Hymenoptera venom hypersensitivity before and during venom exposure. Of these, 20 developed SR to stings or following venom injections during immunotherapy (reactors), while 15 tolerated reexposure to stings or venom injections during immunotherapy without SR (non-reactors). Serum tryptase was estimated at 2, 5 and 24 h after exposure and was compared to a baseline value obtained before or at least 72 h after exposure.

RESULTS

Considering circadian variation of serum tryptase, a relative increase to ≥135% of the baseline value (relative delta bound) was defined to indicate mast cell activation. Such an increase was observed in 17 of 20 reactors (85%), but none of 15 non-reactors. A serum tryptase of ≥11.4 ng/mL following venom exposure was observed in eight of the 20 reactors (40%) and 2 (13.3%) of the 15 non-reactors. Both these non-reactors also had an elevated baseline serum tryptase.

CONCLUSIONS AND CLINICAL RELEVANCE

Serum tryptase values obtained during a suspected hypersensitivity reaction must always be compared to a baseline value. A relative tryptase increase to ≥135% of the baseline value during a suspected hypersensitivity reaction indicates mast cell activation even below 11.4 ng/mL.

Basal serum tryptase as risk assessment for severe Hymenoptera sting reactions in elderly

BACKGROUND

Epidemiologic studies suggest that elderly people are more prone to develop severe anaphylactic reactions. However, the exact cause for this phenomenon remains unclear.

AIMS OF THE STUDY

To study the role of the serum tryptase as a diagnostic parameter for individual risk evaluation and its impact on the severity of allergic reactions in elderly people.

METHODS

Two hundred and seventy-four consecutive patients visiting the Department of Dermatology, Tübingen, Germany, who were diagnosed with honeybee or wasp venom allergy, were included in the study.

RESULTS

Sting reaction severity increased with increased age and tryptase levels (P = 0.001 and P = 0.0003, respectively). Furthermore, we find not only a general increment in tryptase levels in elderly people (P = 0.0001) but also a continuous increase in tryptase concentrations even below the cut-off (11.4 microg/l) with increasing age (P = 0.0026).

CONCLUSIONS

Our data confirm serum tryptase as a risk factor for severe anaphylactic reaction to hymenoptera stings. Furthermore, we give first evidence that basal serum tryptase levels increase continuously with age and being an indicator for either increased mast cell load or reactivity this can at least partly be responsible for the observed aggravated allergic reactions in elderly people. As those patients are at increased risk for life-threatening anaphylactic reactions, it should be considered to adjust VIT especially in elderly patients with elevated tryptase levels as recommended for patients with mastocytosis by increasing venom doses during VIT and by considering its life-long continuation.

Serum concentration of baseline mast cell tryptase: evidence for a decline during long-term immunotherapy for Hymenoptera venom allergy

BACKGROUND

Baseline serum mast cell tryptase concentration (BTC) is thought to reflect the constitutive mast cell load or activity of an individual patient. Little is known about the individual stability of BTC during long-term venom immunotherapy (VIT).

OBJECTIVE

To investigate the intra-individual stability of BTC over time in patients with Hymenoptera venom allergy.

METHODS

Three hundred and two patients were studied. BTC was measured before and at least twice during VIT. At least 4 weeks lay between BTC measurements and the most recent field sting, in-hospital sting, or preceding venom injection. Multifactorial mixed linear models were used to analyse BTC changes over time.

RESULTS

Median observation time was 4.2 years (range 2-12 years). Before VIT, the median BTC was 6.8 microg/L (range 1.14-177 microg/L). The median coefficient of variation (CV) over time was 15.3% (range 1.9-63.8%). The median CV was significantly smaller in patients presenting with an elevated BTC (>11.4 microg/L) than in patients with a normal BTC (11.4%, range 2.6-39.5%; vs. 17.6%, range 1.9- 63.8%; P<0.001). During VIT and after adjusting for age and gender, we found a slight but significant decrease of BTC over time (2.5% per year, 95% confidence interval 2.0-3.0%, P<0.001).

CONCLUSION

Individual variation of BTC during VIT does not rise when BTC is increased before therapy. VIT is associated with a small, but continuous decrease of BTC over time possibly indicating a dampened mast cell function or a decline in mast cell burden.

Mastocytosis and insect venom allergy: diagnosis, safety and efficacy of venom immunotherapy

The most important causative factor for anaphylaxis in mastocytosis are insect stings. The purpose of this review is to analyse the available data concerning prevalence, diagnosis, safety and effectiveness of venom immunotherapy (VIT) in mastocytosis patients. If data were unclear, authors were contacted personally for further information. Quality of evidence (A: high, B: moderate, C: low and D: very low) and strength of recommendation (strong 1 and weak 2) concerning VIT in mastocytosis patients are assessed according to the Grading of Recommendations Assessment, Development and Evaluation and are marked in square brackets. Results of VIT were described in 117 patients to date. The mean rate of side-effects during treatment in studies published so far is 23.9% (7.6% requiring adrenaline) with an overall protection rate of 72%. Based on the review we conclude that (1) mastocytosis patients have a high risk of severe sting reactions in particular to yellow jacket, (2) VIT could be suggested [2] in mastocytosis, (3) probably should be done life long [2], (4) VIT in mastocytosis is accompanied by a higher frequency of side-effects, so (5) special precautions should be taken into account notably during the built up phase of the therapy [2], (6) VIT is able to reduce systemic reactions, but to a lesser extent compared to the general insect venom allergic population [2], so (7) patients should be warned that the efficacy of VIT might be less than optimal and they should continue carrying two adrenaline auto injectors [2].

Clinical immunology review series: an approach to the use of the immunology laboratory in the diagnosis of clinical allergy

In the last 10 years UK immunology laboratories have seen a dramatic increase in the number and range of allergy tests performed. The reasons for this have been an increase in the incidence of immunoglobulin E (IgE)-mediated allergic disease set against a background of greater public awareness and more referrals for assessment. Laboratory testing forms an integral part of a comprehensive allergy service and physicians treating patients with allergic disease need to have an up-to-date knowledge of the range of tests available, their performance parameters and interpretation as well as the accreditation status of the laboratory to which tests are being sent. The aim of this review is to describe the role of the immunology laboratory in the assessment of patients with IgE-mediated allergic disease and provide an up-to-date summary of the tests currently available, their sensitivity, specificity, interpretation and areas of future development.