Mouse connective tissue mast cell proteases tryptase and carboxypeptidase A3 play protective roles in itch induced by endothelin-1

Background

Itch is an unpleasant sensation that can be debilitating, especially if it is chronic and of non-histaminergic origin, as treatment options are limited. Endothelin-1 (ET-1) is a potent endogenous vasoconstrictor that also has the ability to induce a burning, non-histaminergic pruritus when exogenously administered, by activating the endothelin A receptor (ET_AR) on primary afferents. ET-1 is released endogenously by several cell-types found in the skin, including macrophages and keratinocytes. Mast cells express ET_ARs and can thereby be degranulated by ET-1, and mast cell proteases chymase and carboxypeptidase A3 (CPA3) are known to either generate or degrade ET-1, respectively, suggesting a role for mast cell proteases in the regulation of ET-1-induced itch. The mouse mast cell proteases (mMCPs) mMCP4 (chymase), mMCP6 (tryptase), and CPA3 are found in connective tissue type mast cells and are the closest functional homologs to human mast cell proteases, but little is known about their role in endothelin-induced itch.

Methods

In this study, we evaluated the effects of mast cell protease deficiency on scratching behavior induced by ET-1. To investigate this, mMCP knock-out and transgenic mice were injected intradermally with ET-1 and their scratching behavior was recorded and analyzed.

Results

CPA3-deficient mice and mice lacking all three proteases demonstrated highly elevated levels of scratching behavior compared with wild-type controls. A modest increase in the number of scratching bouts was also seen in mMCP6-deficient mice, while mMCP4-deficiency did not have any effect.

Conclusion

Altogether, these findings identify a prominent role for the mast cell proteases, in particular CPA3, in the protection against itch induced by ET-1.

Elevated Serum Tryptase in Non-Anaphylaxis Cases: A Concise Review

One of the most important blood tests in the field of allergy, mast cell tryptase has numerous diagnostic uses, particularly for anaphylactic reactions and for the diagnosis of mastocytosis. However, there are numerous other non-anaphylactic conditions where clinicians may see elevated serum tryptase (hypertryptasemia) and the practicing clinician ought to be aware of these important differential diagnoses. Such conditions include systemic mastocytosis, hematological malignancies, and chronic kidney disease. This article provides a comprehensive, updated summary on the variety of non-anaphylactic conditions where hypertryptasemia may be seen.

Bone lesions in systemic mastocytosis: Bone histomorphometry and histopathological mechanisms

Osteoporosis is considered the most frequent skeletal manifestation of systemic mastocytosis (SM). We performed a retrospective analysis of sixty patients (37 males and 23 females) who underwent a bone biopsy in the assessment of SM or in the assessment of unexplained bone fragility. Thirty-three had simultaneously a bone marrow biopsy with a Jamshidi's needle; this sample was used for immunohistochemical analysis (tryptase, c-KIT. CD20, VCAM-1). Bone biopsy was realized in 42 cases in the assessment of SM to provide histologic proof of the disease and in 18 cases in the assessment of unexplained bone fragility and surprisingly revealed a SM. An increased bone turnover was observed in patients with SM with elevated eroded surfaces, osteoclast number and bone formation rate. In addition to nodules of mast cells (MC), a high number of MC was directly apposed on the trabeculae, affixed on the osteoblasts or the lining cells. The VCAM-1 adhesion protein recognizing α4β7 and α4β1 integrins may be a candidate to explain this particular adherence. One third of the bone marrow biopsies did not exhibit MC nodules or MC infiltration and led to a false negative diagnosis for SM. SM can be discovered in the assessment of fracture or osteoporosis. Transiliac bone biopsy allows for the diagnosis of the disease more accurately than bone marrow biopsy; it also provides a histomorphometric analysis of bone remodeling.

[Mast cell activation syndrome. About a clinical case]

BACKGROUND

Monoclonal mast cell activation syndrome is included in mast cell activation disorders in which, after a diagnostic process, it is not possible to meet the required criteria for a diagnosis of systemic mastocytosis.

CLINICAL CASE

A 73-year-old woman who presented two events of anaphylaxis 15 minutes after the intake of yucca; with a positive skin test, elevated tryptase, and mast cells with abnormal phenotype in the bone marrow biopsy, and without criteria for systemic mastocytosis.

CONCLUSION

The diagnosis of monoclonal mast cell activation syndrome requires high clinical suspicion for patients with recurrent anaphylaxis and elevated tryptase, for whom joint management with hematology is essential.

Mast Cells in the Tumor Microenvironment

Mast cells are tissue-resident, innate immune cells that play a key role in the inflammatory response and tissue homeostasis. Mast cells accumulate in the tumor stroma of different human cancer types, and increased mast cell density has been associated to either good or poor prognosis, depending on the tumor type and stage. Mast cells play a multifaceted role in the tumor microenvironment by modulating various events of tumor biology, such as cell proliferation and survival, angiogenesis, invasiveness, and metastasis. Moreover, tumor-associated mast cells have the potential to shape the tumor microenvironment by establishing crosstalk with other tumor-infiltrating cells. This chapter reviews the current understanding of the role of mast cells in the tumor microenvironment. These cells have received much less attention than other tumor-associated immune cells but are now recognized as critical components of the tumor microenvironment and could hold promise as a potential target to improve cancer immunotherapy.

[Anaphylaxis caused by dermal exposure with cow's milk in an adult with food allergy. A case report]

BACKGROUND

Allergy to cow's milk proteins is the most frequent food allergy and its prevalence has increased in the last decade. Although most patients have symptoms after the intake of dairy milk, other routes of sensitization through skin and mucous membranes have been described.

CASE REPORT

A 31-year-old male patient who is a professional chef and started with oropharyngeal symptoms after the intake of milk. Since he tolerated other dairy products, he did not suppress them from his diet. However, the clinical picture progressed and cutaneous symptoms were added; finally, anaphylaxis occurred by contact with bread dough that contained butter and milk. The patient was treated in the emergency department, where an increase in serum tryptase was verified. Skin prick tests and serological tests were positive for milk and its fractions.

CONCLUSION

Reports of anaphylaxis caused by dermal contact with cow's milk are very scarce and they have been reported only in children. We believe that repeated food handling could favor cutaneous sensitization in adults with a personal history of atopy.

Detection of Mast Cells and Basophils by Immunohistochemistry

Staining cells or tissues with basic dyes was the mainstay of mast cell and basophil detection methods for more than a century following the first identification of these cell types using such methods. These techniques have now been largely supplanted by immunohistochemical procedures with monoclonal antibodies directed against unique constituents of these cell types. Immunohistochemistry with antibodies specific for the granule protease tryptase provides a more sensitive and discriminating means for detecting mast cells than using the classical histochemical procedures, and using antibodies specific for products of basophils (2D7 antigen and basogranulin) has allowed detection of basophils that infiltrate into tissues. The application of immunohistochemistry to detect more than one marker in the same cell has underpinned concepts of mast cell heterogeneity based on differential expression of chymase and other proteases. The double labeling procedures employed have also provided a means for investigating the expression of cytokines and a range of other products. Protocols are here set out that have been used for immunohistochemical detection of mast cells and basophils and their subpopulations in human tissues. Consideration is given to pitfalls to avoid and to a range of alternative approaches.

Mast Cell Activation: When the Whole Is Greater than the Sum of Its Parts

Mast cell activation syndrome (MCAS) is a heterogeneous and rare disorder with episodic and severe activation of mast cells. Because symptoms of mast cell activation are nonspecific, it is important to base the diagnosis on best available clinical and scientific evidence, and not make it one of exclusion. MCAS, much like the mast cell itself, as a whole is greater than the sum of its proposed diagnostic criteria. When each component is considered in isolation, criteria can seem nonspecific, and thus, a broad constellation of symptoms can be attributed to MCAS when they may be due to other disease processes.

Peptides of major basic protein and eosinophil cationic protein activate human mast cells

The eosinophil granule proteins, major basic protein (MBP) and eosinophil cationic protein (ECP), activate mast cells during inflammation; however the mechanism responsible for this activity is poorly understood. We found that some theoretical tryptase-digested fragments of MBP and ECP induced degranulation of human cord blood-derived mast cells (HCMCs). The spectrum of activities of these peptides in HCMCs coincided with intracellular Ca²⁺ mobilization activities in Mas-related G-protein coupled receptor family member X2 (MRGPRX2)-expressing HEK293 cells. Two peptides corresponding to MBP residues 99–110 (MBP (99–110)) and ECP residues 29–45 (ECP (29–45)), respectively, induced degranulation of HCMCs and intracellular Ca²⁺ mobilization in MRGPRX2-expressing HEK293 cells in a concentration-dependent manner. Stimulation with MBP (99–110) or ECP (29–45) induced the production of prostaglandin D2 by HCMCs. The activities of MBP (99–110) and ECP (29–45) in both HCMCs and MRGPRX2-expressing HEK293 cells were inhibited by MRGPRX2-specific antagonists. In conclusion, these results indicated that MBP and ECP fragments activate HCMCs, and it may occur via MRGPRX2. Our findings suggest that tryptase-digested fragments of eosinophil cationic proteins acting via the MRGPRX2 pathway may further our understanding of mast cell/eosinophil communication.

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Mast cell activators were found in tryptase-fragments from MBP and ECP.

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These fragments activated MRGPRX2-expressing cells.

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MRGPRX2 antagonists inhibited mast cell activation caused by active fragments.

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Active fragments may work as mediators in mast cell/eosinophil communication.

Survey of Mast Cell Mediator Levels from Patients Presenting with Symptoms of Mast Cell Activation

INTRODUCTION

Although 4 mast cell mediators can be routinely measured, the results of initial testing to evaluate symptoms of mast cell activation have not been widely reported.

OBJECTIVE

We examined the results of mast cell mediator tests used to assess patients with mast cell activation symptoms during a 5-year time span.

METHODS

After excluding patients with alternative diagnoses, records of 108 patients were reviewed for initial mediator test results. Mediators included serum tryptase plus urinary N-methyl histamine (N-MH), leukotriene (LT)E4, and 11β-prostaglandin (PG) F2α or 2,3-dinor-11β-PGF2α (BPG).

RESULTS

Most commonly, either a single measured elevation of 1 mediator (48.1%) or elevations of 2 (33.3%) mediators was found at baseline, during symptoms or at both time points. Elevated levels of a single mediator in order of frequency were: BPG > tryptase > LTE4 > N-MH, and for two mediators: BPG + tryptase (n = 16 cases) > BPG + LTE4 (n = 9) > BPG + N-MH (n = 6). Elevations in 3 mediators (n = 8) or 4 mediators (n = 2) were much less frequent. Monoclonal mast cell activation syndrome (n = 6), and systemic and cutaneous mastocytosis (n = 4) were also infrequent. Baseline plus symptom-associated tryptase values were obtained in only 7 patients.

CONCLUSIONS

This survey suggests that elevations of 1 or 2 mediators are the most common (total 81.4% of cases) findings from initial tests for mast cell activation. Elevated levels of BPG were most commonly found both singly and in combination with other mediators, followed by the finding of elevated levels of tryptase. Baseline plus symptom-associated tryptase levels were measured in only a minority of patients.

The release of tryptase from mast cells promote tumor cell metastasis via exosomes

Background

Cancer cells release exosomes and can be taken up by mast cells (MCs), but the potential functional effects of MCs on tumor metastasis remain unknown.

Method

Exosomes were isolated from the lung adenocarcinoma cell line A549, and the uptake of PKH26-labeled exosomes by bone marrow MCs was examined via flow cytometry and fluorescence microscopy. Cytokines and tryptase in MC supernatant were analyzed using an ELISA kit, and the presence of tryptase was evaluated by Western blotting. Cell proliferation and migration were determined through CCK-8 and transwell assays. Proteins in the tryptase-JAK-STAT signaling pathway were detected by Western blotting.

Results

In this study, we show that exosomes from A549 cells can be taken up by MCs. Moreover, A549 exosomes contain stem cell factor (SCF) to MCs and subsequently induce the activation of MCs through SCF-KIT signal transduction, which leads to MC degranulation and the release of tryptase. Tryptase accelerates the proliferation and migration of human umbilical vein endothelial cells (HUVECs) through the JAK-STAT signaling pathway.

Conclusions

Our results reveal a mechanism for metastasis in which exosomes can transfer SCF to and activate MCs, which can affect the release of tryptase and the angiogenesis of HUVECs.

Giardia excretory-secretory proteins modulate the enzymatic activities of mast cell chymase and tryptase

BACKGROUND

Mast cells are involved in the host immune response controlling infection with the non-invasive intestinal protozoan parasite Giardia intestinalis. Experimental infections in rodents with G. intestinalis showed increased intestinal expression of mucosal and connective mast cell specific proteases suggesting that both mucosal and connective tissue mast cells are recruited and activated during infection. During infection Giardia excretory-secretory proteins (ESPs) with immunomodulatory capacity are released. However, studies investigating potential interactions between Giardia ESPs and the connective tissue mast cell specific serine proteases, i.e. human chymase and mouse mast cell protease (mMCP)-4 and, human and mouse tryptase (mMCP-6) remain scarce.

RESULTS

We first investigated if soluble Giardia proteins (sGPs), which over-lap extensively in protein content with ESP fractions, from the isolates GS, WB and H3, could induce mast cell activation. sGPs induced a minor activation of bone marrow derived mucosal-like mast cells, as indicated by increased IL-6 secretion and no degranulation. Furthermore, sGPs were highly resistant to degradation by human tryptase while human chymase degraded a 65 kDa sGP and, wild-type mouse ear tissue extracts degraded several protein bands in the 10 to 75 kDa range. In striking contrast, sGPs and ESPs were found to increase the enzymatic activity of human and mouse tryptase and to reduce the activity of human and mouse chymase.

CONCLUSION

Our finding suggests that Giardia ssp. via enhancement or reduction of mast cell protease activity may modulate mast cell-driven intestinal immune responses. ESP-mediated modulation of the mast cell specific proteases may also increase degradation of tight junctions, which may be beneficial for Giardia ssp. during infection.

Serum Baseline Tryptase Level as a Marker for the Severity of Anaphylaxis

BACKGROUND

Anaphylaxis is a severe and potentially fatal allergic disease or hypersensitivity reaction with variable clinical presentation. Biomarkers in anaphylaxis could be useful to improve diagnosis, to allow endotyping of patients, and to predict risk.

OBJECTIVE

To investigate the role of serum basal tryptase (sBT) levels in the management of patients with anaphylaxis.

METHODS

Patients with at least 1 episode of anaphylaxis were selected among those who attended the Allergy Clinics of the Clinical Hospital of the Ribeirão Preto Medical School, University of São Paulo, Brazil, upon evaluation by allergy/immunology specialists of our medical staff. Demographic and clinical data were obtained using a structured questionnaire. sBT levels were determined using the ImmunoCAP Tryptase immunoassay.

RESULTS

57 patients (56.1% female) with a median age of 35 years (range 7-87 years) participated in the study. sBT levels ranged from 2.57 to 21.19 ng/mL (mean 5.17 ng/mL), with no significant differences in patients with anaphylaxis due to different triggers. Mean levels were 4.93; 5.2; 5.41, and 5.24 ng/mL for patients who had anaphylaxis due to Hymenoptera venom (n = 17), foods (n = 13), drugs (n = 13), and idiopathic disease (n = 14), respectively. Significantly higher sBT levels were observed in patients with severe anaphylaxis (grade IV) than in patients with mild-moderate disease (grades II/III) (mean levels 6.61 vs. 4.71 ng/mL, respectively).

CONCLUSION

High sBT levels may help to identify patients at increased risk of more severe anaphylaxis, prompting physicians to initiate immediate therapy to avoid further acute episodes.

Skewed Lymphocyte Subpopulations and Associated Phenotypes in Patients with Mastocytosis

BACKGROUND

Mastocytosis is a clonal mast cell disorder associated with elevated mast cell mediators, which themselves have been reported to affect lymphocyte function. However, the impact of an expanded mast cell compartment on lymphocyte subpopulations, and their correlation with clinical phenotypes in patients with indolent systemic mastocytosis (ISM), has not been explored.

OBJECTIVE

To examine the immunophenotype of circulating lymphocytes in patients with ISM compared with healthy adult controls and examine relationships with aspects of clinical disease.

METHODS

We examined lymphocyte subsets in 20 adult patients with ISM and 40 healthy adult volunteers by multiparameter flow cytometry. Results were correlated with clinical characteristics.

RESULTS

Patients with ISM exhibited a significantly lower median frequency and absolute cell count of both circulating CD8⁺ T cells and natural killer cells accompanying a significantly increased ratio of CD4⁺/CD8⁺ T cells when compared with healthy volunteers. Stratification of our ISM patient cohort according to clinical manifestations revealed that CD19⁺CD21^lowCD38^low B cells were significantly higher in patients with a history of autoimmune disease and counts of terminally differentiated CD4⁺ T cells were significantly higher in patients with osteoporosis or osteopenia.

CONCLUSIONS

Several circulating lymphocyte subpopulations in patients with ISM were significantly different when compared with healthy controls; in specific lymphocyte subsets, this lymphocyte skewing correlated with clinical observations including osteoporosis and autoimmune disease. These data suggest the need for further studies on abnormalities in lymphocyte subsets and the attendant clinical consequences in both mast cell proliferative and activation disorders.

Why the 20% + 2 Tryptase Formula Is a Diagnostic Gold Standard for Severe Systemic Mast Cell Activation and Mast Cell Activation Syndrome

Mast cell activation syndrome (MCAS) is a condition characterized by recurrent episodes of clinically relevant, systemic, severe reactions to mast cell (MC)-derived mediators released in the context of anaphylaxis or another acute MC-related event. It is important to document MC involvement in these reactions in order to establish the diagnosis MCAS. The most specific and reliable marker of systemic MC activation is an acute and substantial event-related (transient) increase in the serum tryptase level over the individual's baseline value. However, the baseline level of tryptase varies depending on the underlying disease and the genetic background. For example, an estimated 3-5% of healthy individuals exhibit duplications or multiple copies of the TPSAB1 gene encoding for alpha-tryptase, and over 30% of all patients with myeloid neoplasms, including mastocytosis, have elevated basal tryptase levels. Therefore, it is of utmost importance to adjust the event-related diagnostic (MCAS-confirming) increase in tryptase over the individual baseline in a robust approach. To address this challenge, the 20% + 2 formula was proposed by the consensus group in 2012. Since then, this approach has been validated in clinical practice by independent groups and found to be sound. In the current article, we discuss the emerging importance and value of the 20% + 2 formula in clinical practice and its role as a criterion of severe systemic MC activation and MCAS.

Exclusive Bee Venom Allergy: Risk Factors and Outcome of Immunotherapy

INTRODUCTION

Venom immunotherapy (VIT) is considered to be the gold-standard treatment for patients with Hymenoptera venom allergy. Data regarding VIT in bee venom (BV) allergic patients are scarce.

AIM

The aim of this study was to evaluate the outcome of VIT in patients with exclusive BV allergy and to try to define risk factors for VIT-induced systemic reactions (VIT-ISR) and VIT failure.

METHODS

This is a retrospective study including data from all BV allergic patients that were treated by VIT in the Allergy Unit at the Meir Medical Center in the years 1995-2018.

RESULTS

Two hundred and forty-seven patients with exclusive BV allergy were included; 206 (83.4%) preferred to undergo rush buildup. Sixty-nine patients (27.9%) had at least 1 reaction during buildup, with the c-kit mutation being the only significant risk factor (100 vs. 28.9%, p = 0.02). Female gender (25.4 vs. 13.3%, p = 0.04), conventional buildup schedule (26.8 vs. 14.1%, p = 0.04), and c-kit mutation (100 vs. 16.8%, p < 0.01) but not tryptase level were found to be significantly more frequent in recurrent reactors. Females (20.3 vs. 9%, p = 0.03), patients with severe systemic reaction to the index sting (24.3 vs. 9.5%, p = 0.004), and c-kit mutation (66 vs. 12%, p = 0.05) but not tryptase level were found to be risk factors for severe systemic reactions.

CONCLUSION

Despite the considerably high rate of VIT-ISR in patients with exclusive BV allergy, VIT can be performed safely and efficiently. C-kit mutation, and not basal serum tryptase level, seems to be a preferable biomarker for VIT-ISR in these patients.

Physiological Roles of Mast Cells: Collegium Internationale Allergologicum Update 2019

Mast cells are immune cells which have a widespread distribution in nearly all tissues. These cells and their mediators are canonically viewed as primary effector cells in allergic disorders. However, in the last years, mast cells have gained recognition for their involvement in several physiological and pathological conditions. They are highly heterogeneous immune cells displaying a constellation of surface receptors and producing a wide spectrum of inflammatory and immunomodulatory mediators. These features enable the cells to act as sentinels in harmful situations as well as respond to metabolic and immune changes in their microenvironment. Moreover, they communicate with many immune and nonimmune cells implicated in several immunological responses. Although mast cells contribute to host responses in experimental infections, there is no satisfactory model to study how they contribute to infection outcome in humans. Mast cells modulate physiological and pathological angiogenesis and lymphangiogenesis, but their role in tumor initiation and development is still controversial. Cardiac mast cells store and release several mediators that can exert multiple effects in the homeostatic control of different cardiometabolic functions. Although mast cells and their mediators have been simplistically associated with detrimental roles in allergic disorders, there is increasing evidence that they can also have homeostatic or protective roles in several pathophysiological processes. These findings may reflect the functional heterogeneity of different subsets of mast cells.

Relationship between mast cells and E-cadherin in odontogenic keratocysts and radicular cysts

OBJECTIVE

This study aimed to evaluate tryptase and E-cadherin protein expression in odontogenic keratocysts (OKCs) and radicular cysts (RCs) and their relationship with lesion size.

MATERIALS AND METHODS

Thirty OKC and 30 RC cases were analyzed by immunohistochemistry. Tryptase expression was quantitatively assessed using the quantification of mast cells, and expression of E-cadherin was semi-quantitatively analyzed estimating the proportion of positive cells: 1 = less than 25% of immunopositive cells; 2 = 26 to 50% of immunopositive cells; 3 = 51 to 75% of immunopositive cells; 4 = more than 75% of immunopositive cells. Data on cystic lesion sizes were obtained from patients' clinical files, based on previous radiographic exams, and the lesions were categorized into three groups: group 1 (< 2 to 2 cm); group 2 (> 2 to 4 cm), and group 3 (> 4 cm).

RESULTS

Higher mast cell means were found for RCs, with the predominance of degranulated mast cells in both OKCs and RCs (p = 0.082). Concerning the epithelial component, a higher concentration of degranulated mast cells was detected in RCs (p = 0.000). Regarding connective tissue, degranulated mast cells were more evident in OKCs (p = 0.762). A negative correlation was observed between E-cadherin expression and total number of mast cells (p = 0.011), degranulated mast cells (p = 0.040), and degranulated mast cells in both superficial (p = 0.035) and deep connective tissues (p = 0.009). Concerning lesion size, a negative correlation with total number of mast cells (p = 0.016) and number of degranulated mast cells (p = 0.049) was observed, both in the epithelial components. Herein, the larger the lesion size, the lower the number of degranulated mast cells in the epithelium (r = - 0.271; p = 0.49), suggesting that these cells play a role in the initial cystic expansion phase.

CONCLUSION

The higher expression of tryptase in degranulated mast cells was linked to a lower expression of E-cadherin, which may be related to a change in the epithelial permeability in these lesions, contributing to increased cystic content and lesion growth.

CLINICAL RELEVANCE

Evidence of the relationship between mast cells and E-cadherin in the growth of odontogenic cysts was studied.

Multiple vertebral fractures as the first manifestation of systemic mastocytosis

Systemic mastocytosis is a clonal disease of the mast cell progenitors of the bone marrow. The clinical picture varies from asymptomatic (indolent) to highly aggressive (mast cell leukemia). Up to one-third of patients with SM have osteoporosis and fractures. The following is an analysis of the case of a young patient with multiple fractures as the first manifestation of SM.

Increased mast cell number is associated with a decrease in beta-cell mass and regeneration in type 2 diabetic rats

The role of mast cells (MCs) in type 2 diabetes (T2D) is not thoroughly studied as much as in T1D. Therefore in the current study we investigated correlation between these cells and various parameters of islets of Langerhans (IOL) in rats which were equally divided (n = 40) into; control and diabetic groups. We detected a significantly increased (p < 0.05) MC count (MCC) in the diabetic IOL compared to the control, together with a noticeable intra-islet seeding of these cells which displayed a tryptase positive immunostaining. A significant positive correlation (p < 0.05) between MCC and the % of glucagon cells per islet was detected in DM, unlike mass of the islets, mass of β-cells, and % of β-cells per islet which were negatively correlated with MCC. Similarly, there was a negative correlation between MCC with β-cell proliferation and neogenesis frequency in DM. This highlights the potential association between the increased MC number and the diminished islet`s mass as well as regeneration which may fasten the progression of T2D.

Progenitor mast cells and tryptase in Q fever

Q fever is an infectious disease due to Coxiella burnetii. Following a primary-infection, C. burnetii may persist in some patients, leading to endocarditis and vascular infections. Mast cells (MCs), known for their role in allergic diseases, innate immunity and cardiac function, are produced by bone marrow, circulate as progenitors in the bloodstream and reach tissues for their maturation and activation. The latter may be estimated by measuring serum tryptase levels. We wondered if MC progenitors and tryptase were affected in Q fever. We showed a decrease in MC progenitor count in Q fever patients whereas serum tryptase levels were increased. Taken together, our results show alterations of MC numbers and activity in Q fever patients, suggesting that MC are involved in Q fever pathophysiology.

The effects of different sampling techniques on peripheral post mortem tryptase levels: a recommended sampling method

Different sampling techniques can impact on post mortem tryptase levels. A previous study demonstrated significantly lower femoral post mortem total tryptase levels in samples collected via transcutaneous aspiration compared with directly sampling during internal examination. However, an outlier with high tryptase level was noted in one transcutaneous aspiration sample. This 6-month prospective study compared total post mortem tryptase levels between 21 paired aspirated venous and arterial femoral blood samples, and 19 paired aspirated and cutdown femoral venous blood samples in non-anaphylactic deaths only. No statistical differences were demonstrated between the different sampling methods. However, four outlier cases with higher tryptase levels in aspirated arterial and femoral cutdown samples compared with aspirated venous femoral samples were noted. The reasons for the outliers may be due to the bloods collected from these two methods being contaminated by central arterial and venous blood with high tryptase levels respectively. None of the aspirated venous femoral post mortem tryptase levels were above recognized post mortem tryptase cutoff to diagnose anaphylaxis. This study recommends aspirating blood samples from a clamped femoral/external iliac vein for post mortem tryptase analysis should be defined as the gold standard. Further study using the recommended sampling method on post mortem tryptase levels in non-anaphylactic and anaphylactic cases is warranted.