Martin Metz

Mast cells in the promotion and limitation of chronic inflammation

Summary:  Observations of increased numbers of mast cells at sites of chronic inflammation have been reported for over a hundred years. Light and electron microscopic evidence of mast cell activation at such sites, taken together with the known functions of the diverse mediators, cytokines, and growth factors that can be secreted by appropriately activated mast cells, have suggested a wide range of possible functions for mast cells in promoting (or suppressing) many features of chronic inflammation. Similarly, these and other lines of evidence have implicated mast cells in a variety of adaptive or pathological responses that are associated with persistent inflammation at the affected sites. Definitively characterizing the importance of mast cells in chronic inflammation in humans is difficult. However, mice that genetically lack mast cells, especially those which can undergo engraftment with wildtype or genetically altered mast cells, provide a means to investigate the importance of mast cells and specific mast cell functions or products in diverse models of chronic inflammation. Such work has confirmed that mast cells can significantly influence multiple features of chronic inflammatory responses, through diverse effects that can either promote or, perhaps more surprisingly, suppress aspects of these responses.

Mast cells promote homeostasis by limiting endothelin-1-induced toxicity

Endothelin-1 (ET-1) is a 21-amino-acid peptide, derived from vascular endothelial cells, with potent vasoconstrictor activity. ET-1 has been implicated in diverse physiological or pathological processes, including the vascular changes associated with sepsis. However, the factors that regulate ET-1-associated toxicity during bacterial infections, or in other settings, are not fully understood. Both the pathology associated with certain allergic and autoimmune disorders, and optimal host defence against bacterial and parasitic infections are mediated by mast cells. In vitro, mast cells can produce ET-1 (ref. 11), undergo ET-1-dependent and endothelin-A receptor (ETA)-dependent activation, and release proteases that degrade ET-1 (ref. 14). Although the potential relationships between mast cells and the ET-1 system thus may be complex, the importance of interactions between ET-1 and mast cells in vivo is obscure. Here we show that ETA-dependent mast-cell activation can diminish both ET-1 levels and ET-1-induced pathology in vivo, and also can contribute to optimal survival during acute bacterial peritonitis. These findings identify a new biological function for mast cells: promotion of homeostasis by limiting the toxicity associated with an endogenous mediator.

Control of murine hair follicle regression (catagen) by TGF-β1 in vivo

The regression phase of the hair cycle (catagen) is an apoptosis‐driven process accompanied by terminal differentiation, proteolysis, and matrix remodeling. As an inhibitor of keratinocyte proliferation and inductor of keratinocyte apoptosis, transforming growth factor β1 (TGF‐β1) has been proposed to play an important role in catagen regulation. This is suggested, for example, by maximal expression of TGF‐β1 and its receptors during late anagen and the onset of catagen of the hair cycle. We examined the potential involvement of TGF‐β1 in catagen control. We compared the first spontaneous entry of hair follicles into catagen between TGF‐β1 null mice and age‐matched wild‐type littermates, and assessed the effects of TGF‐β1 injection on murine anagen hair follicles in vivo. At day 18 p.p., hair follicles in TGF‐β1 —/— mice were still in early catagen, whereas hair follicles of +/+ littermates had already entered the subsequent resting phase (telogen). TGF‐β1 — /— mice displayed more Ki‐67‐positive cells and fewer apoptotic cells than comparable catagen follicles from +/+ mice. In contrast, injection of TGF‐β1 into the back skin of mice induced premature catagen development. In addition, the number of proliferating follicle keratino‐cytes was reduced and the number of TUNEL + cells was increased in the TGF‐β1‐treated mice compared to controls. Double visualization of TGF‐β type II receptor (TGFRII) and TUNEL reactivity revealed colocalization of apoptotic nuclei and TGFRII in catagen follicles. These data strongly support that TGF‐β1 ranks among the elusive endogenous regulators of catagen induction in vivo, possibly via the inhibition of keratinocyte proliferation and induction of apoptosis. Thus, TGF‐βRII agonists and antagonists may provide useful therapeutic tools for human hair growth disorders based on premature or retarded catagen development (effluvium, alopecia, hirsutism).—Foitzik, K., Lindner, G., Mueller‐Roever, S., Maurer, M., Botchkareva, N., Botchkarev, V., Handjiski, B., Metz, M., Hibino, T., Soma, T., Dotto, G. P., Paus, R. Control of murine hair follicle regression (catagen) by TGF‐β1 in vivo. FASEB J. 14, 752–760 (2000)

Successful treatment of solar urticaria with anti- immunoglobulin E therapy

anaesthesiologists and oncologists), practising doctors treated anaphylactic patients regularly. The average number of treated patients per practice was low, but considering the high number of practising doctors, they deliver a broad number of anaphylactic cases. The reported triggers of anaphylaxis are in line with data from the literature. However, the most common trigger factor of anaphylaxis reported by these doctors, who perform SCIT on a regular basis, was SCIT. This observation points to the necessity of gaining more information on severe reactions during SCIT, which are probably underreported. There is a possibility that the reported anaphylactic reactions were not diagnosed properly, as only 19% of the practitioners were specialized in allergy. A recall-bias also needs consideration. Still, our data clearly show that SCIT seems to be an important cause of anaphylaxis in private practice and are in line with a previous survey from Bernstein et al. (4). In conclusion, anaphylaxis is relevant in private practices and more epidemiological data are urgently needed.

Quality of life in patients with chronic urticaria is differentially impaired and determined by psychiatric comorbidity

Background  Chronic urticaria (CU), one of the most common skin disorders, is characterized by spontaneous recurrent bouts of weals and pruritus and associated with severely impaired quality of life (QoL).

Omalizumab is an effective and rapidly acting therapy in difficult-to-treat chronic urticaria: A retrospective clinical analysis

BACKGROUND Omalizumab (anti-IgE) therapy is effective and safe in chronic urticaria (CU) in placebo-controlled clinical trials but real life clinical data are scarce. OBJECTIVE To better understand the effects of omalizumab in CU patients treated outside of clinical trials. METHODS In this retrospective clinical analysis, we assessed responder rates, optimal dosage, response to up-/downdosing, time to relief of symptoms, rates of return and time of relapse after omalizumab administration, and safety in 51 CU patients, 20 with chronic spontaneous urticaria (CSU) alone, 21 with different forms of chronic inducible urticaria (CindU) and 10 with both. RESULTS Omalizumab treatment led to complete remission in 83% of CSU and 70% of CindU patients. When starting with 150mg omalizumab 4 weekly, only 2/15 CSU and 7/17 CindU patients required updosing to achieve complete remission. In CSU, 57% of complete responses occurred within week one, all on the first day. Relapses were 2-8 weeks in all but six patients, where they were <4 months. Omalizumab was safe. Efficacy was not correlated to baseline IgE levels. CONCLUSION Clinical experience from more than 1250 injections in 51 patients over four years indicates that omalizumab is a rapidly acting, highly effective and safe drug in CSU and CindU patients. Our observations in a real life clinical setting support the recommendation of current EAACI/GA(2)LEN/EDF/WAO guideline for the management of urticaria to use omalizumab to treat urticaria patients.

The definition and diagnostic testing of physical and cholinergic urticarias--EAACI/GA2LEN/EDF/UNEV consensus panel recommendations.

The recommendations for the definition and diagnosis presented in this position paper are the result of a panel consensus meeting held in December 2008 in Berlin. This consensus meeting was a joint initiative of EAACI (European Academy of Allergology and Clinical Immunology) Dermatology Section, the EU‐funded network of excellence, GA2LEN (Global Allergy and Asthma European Network), the EDF (European Dermatology Forum) and UNEV (urticaria network e.V.). The aim of these recommendations is to improve the diagnosis and management of patients with physical urticaria or cholinergic urticaria and to promote research and a better understanding of these diseases. Our recommendations used the paper produced by a 1996 expert meeting ( 1 ) and they acknowledge the latest changes in our understanding of physical urticarias and cholinergic urticaria as well as the recent development of novel diagnostic tools. In addition, this consensus paper highlights areas of need for further research.

Mast cells orchestrate type 2 immunity to helminths through regulation of tissue-derived cytokines

Mast cells (MCs) are potent inflammatory cells that are distributed throughout mucosal barrier tissues and respond rapidly to pathogenic stimuli. During helminth infections, MCs play an important role as late-stage effectors. However, it is currently unknown whether MCs contribute to the early innate events that determine the priming of adaptive immunity. MC-deficient mouse strains and mice treated with the MC stabilizing agent cromolyn sodium had dramatically reduced Th2 priming and type 2 cytokine production and harbored increased parasite burdens following infection with gastrointestinal helminths (Heligmosomoides polygyrus bakeri and Trichuris muris). In addition, early production of the tissue-derived cytokines IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) was significantly diminished in MC-deficient mice and resulted in decreased numbers of infection-elicited IL-25–dependent (Lin−CD45−)CD34+Sca-1+ progenitors, which produced type 2 cytokines and could be differentiated into mast cells ex vivo. Finally, repair of MC deficiency increased production of IL-25, IL-33, and TSLP, restored progenitor cell numbers and Th2 priming, and reduced parasite burden. Our data reveal an innate IgE-independent role for MCs in orchestrating type 2 immune responses via the regulation of IL-25, IL-33, and TSLP.

Skin mast cells control T cell-dependent host defense in Leishmania major infections

Mast cells (MCs) initiate protective im‐ munity against bacteria. Here we demonstrate that MCs also contribute to the control of parasitic skin infections by Leishmania major. L. major‐infected MC‐defi‐cient KitW/KitW‐v mice developed markedly larger skin lesions than did normal Kit+/+ mice (>2‐fold), and cutaneous reconstitution with MCs resulted in normalization of lesion development. KitW/KitW‐v lesions contained significantly more parasites, and infections resulted in enhanced spreading of parasites to the spleens as compared to controls. In addition, recruitment of proinflammatory neutrophils, macrophages, and dendritic cells (DCs) in infected mice was MC dependent. In the absence of MCs, reduced numbers of lesional DCs were associated with decreased production of Th1‐promoting interleukin (IL)‐12. Antigen‐specific T cell priming was delayed in KitW/KitW‐v mice and cytokine responses were skewed towards Th2. Notably, local skin MC reconstitution at sites of infection was sufficient for the induction of systemic protection. Thus, MC‐mediated control of L. major infections is not limited to the induction of local inflammation. Instead, MCs contribute significantly to local DC recruitment, which mediates protective immunity. These findings extend the view of MCs as salient sentinels of innate immunity to complex host defense reactions against intracellular pathogens.—Maurer, M., Lopez Kostka, S., Siebenhaar, F., Moelle, K., Metz, M., Knop, J., von Stebut, E. Skin mast cells control T cell‐dependent host defense in Leishmania major infections. FASEB J. 20, 2460–2467 (2006)

Anti-Immunoglobulin E Treatment of Patients with Recalcitrant Physical Urticaria

In physical urticaria, exogenous physical factors such as thermal triggers, solar radiation and mechanic triggers including friction or pressure are responsible for the elicitation of symptoms in the skin of patients. Avoidance of the respective stimulus is usually difficult or impossible, and many patients are not sufficiently treated with standard antihistamines. We report that treatment with omalizumab (Xolair®) of 7 patients with physical urticarias [solar urticaria (n = 2), urticaria factitia/symptomatic dermographism (n = 2), cold urticaria, delayed pressure urticaria and localized heat urticaria] resulted in complete symptom control within days after the first injection in 5 patients. In 1 patient, symptoms improved after increasing the dose of omalizumab, and 1 patient with localized heat urticaria did not respond significantly to treatment. Before anti-immunoglobulin E treatment, all patients had suffered from their physical urticaria for years and had had numerous unsuccessful therapies. The overall excellent responses to omalizumab treatment reported here indicate that anti-immunoglobulin E is a safe and effective treatment for recalcitrant physical urticarias.