The role of basophils and mast cells in acute and late reactions in the skin

Mast cells and basophils in cutaneous immune responses

Mast cells and basophils share some functions in common and are generally associated with T helper 2 (Th2) immune responses, but taking basophils as surrogate cells for mast cell research or vice versa for several decades is problematic. Thus far, their in vitro functions have been well studied, but their in vivo functions remained poorly understood. New research tools for their functional analysis in vivo have revealed previously unrecognized roles for mast cells and basophils in several skin disorders. Newly developed mast cell-deficient mice provided evidence that mast cells initiate contact hypersensitivity via activating dendritic cells. In addition, studies using basophil-deficient mice have revealed that basophils were responsible for cutaneous Th2 skewing to haptens and peptide antigens but not to protein antigens. Moreover, human basophils infiltrate different skin lesions and have been implicated in the pathogenesis of skin diseases ranging from atopic dermatitis to autoimmune diseases. In this review, we will discuss the recent advances related to mast cells and basophils in human and murine cutaneous immune responses.

Amelioration of skewed Th1/Th2 balance in tumor-bearing and asthma-induced mice by oral administration of Agaricus blazei extracts

We showed in a previous study that hot-water extracts of Agaricus blazei (Agaricus extracts) had anti-tumor activity to Meth A fibrosarcoma, but it remains unclear whether the Agaricus extracts ameliorate the skewed balance of type-1 T helper (Th1) and type-2 T helper (Th2) cells. We examined whether Agaricus extracts effect the skewed Th1/Th2 balance in tumor-bearing and asthma-induced mice. When Meth A-bearing mice were given orally either Agaricus extracts or water once a day starting 5 days after tumor implantation, spleen T cells, prepared from tumor-bearing mice treated with Agaricus extracts, in response to anti-CD3 monoclonal antibody produced significantly higher levels of interferon gamma (IFN-gamma) than that of controls. The mRNA expression of IFN-gamma-inducing protein 10 and the frequency of CD69(+) or CD49d(+) cells, among activated T cells infiltrated into tumors, significantly increased in Agaricus-treated mice, compared with those of tumor-controls. In asthma-induced mice, treatment with the Agaricus extracts caused significant downregulation of OVA-specific antibody responses of IgG1 and IgE but not of IgG2a, and significantly decreased total cell numbers, levels of interleukin 5, and eosinophil numbers in bronchial alveolar lavage fluids. IFN-gamma production by anti-CD3-stimulated spleen cells, obtained from Agaricus-treated mice, significantly increased. Our results strongly suggest that oral administration of Agaricus extracts ameliorates the Th1/Th2 balance from the Th2-skewed conditions.

Mast cells: novel clinical perspectives from recent insights

Mast cells are still generally viewed as mediators of type I allergic or pseudoallergic reactions. Research over the past 10 years revealed that our view was too small and that mast cells are of key importance in innate immunity and also types II, III and IV adaptive immune reactions. Understanding their role in modulating and amplifying of inflammatory responses provides important insights into the pathogenesis of skin diseases such as psoriasis, atopic dermatitis, bullous pemphigoid or the control of infections. This helps us to understand the course of these diseases, their trigger mechanisms, and, the new role of agents, which can modulate the function of mast cells. These insights will help to develop new therapeutic approaches.

Histamine N-methyltransferase 939A>G polymorphism affects mRNA stability in patients with acetylsalicylic acid-intolerant chronic urticaria

BACKGROUND

Histamine plays an important role in allergic inflammation. Histamine levels are regulated by histamine N-methyltransferase (HNMT).

OBJECTIVE

To investigate the functional variability of HNMT gene in relation to genetic polymorphisms in patients with aspirin intolerant chronic urticaria (AICU).

METHODS

Two single-nucleotide polymorphisms of the HNMT gene (314C>T, 939A>G) were genotyped in chronic urticaria patients. The functional variability of 3'-untranslated region polymorphism (3'-UTR) was assessed using the pEGFP-HNMT 3'-UTR reporter construct to examine mRNA stability and fluorescence-tagged protein expression. The HNMT enzymatic activities related to the 939A>G polymorphism were examined both in the human mast cells (HMC-1) transfected with the pHNMT CDS-3'-UTR construct and in the patients' red blood cells (RBCs). Histamine release from the basophils of AICU patients was examined.

RESULTS

The 939A>G polymorphism was significantly associated with the AICU phenotype, while no association was found with the 314C>T polymorphism. An in vitro functional study using HMC-1 cells demonstrated that the 939A allele gave lower levels of HNMT mRNA stability, HNMT protein expression, and HNMT enzymatic activity and higher histamine release than the 939G allele. The in vivo functional study demonstrated that the AICU patients with the 939A allele had lower HNMT activity in RBC lysates and higher histamine release from their basophils.

CONCLUSION

The HNMT 939A>G polymorphism lowers HNMT enzymatic activity by decreasing HNMT mRNA stability, which leads to an increase in the histamine level and contributes to the development of AICU.

Super-oxidized solution inhibits IgE-antigen-induced degranulation and cytokine release in mast cells

Activation of the high affinity IgE receptor (Fc epsilonRI) through IgE-antigen complexes induces mast cell degranulation, synthesis of lipid mediators and cytokine production. These effects are involved in Type I hypersensitivity reactions and controlling them has been the main objective of many anti-allergic therapies. Here we report that pretreatment of murine bone marrow derived mast cells (BMMC) with super-oxidized solution (SOS) inhibits Fc epsilonRI dependent-beta hexosaminidase and cytokine release. This effect is exerted without altering total protein tyrosine phosphorylation, MAPK activation, cytokine mRNA accumulation or calcium mobilization after Fc epsilonRI triggering. Our data suggest that this neutral pH-SOS acts like a mast cell-membrane stabilizer inhibiting the cell machinery for granule secretion without altering the signal transduction pathways induced by IgE-antigen receptor crosslinking.

Targeted mast cell silencing protects against joint destruction and angiogenesis in experimental arthritis in mice

OBJECTIVE

Induction of arthritis with autoantibodies against glucose-6-phosphate isomerase (GPI) is entirely independent of T cells and B cells but is strictly dependent on the presence of mast cells. Here, we used this disease model to analyze whether exclusive intraarticular mast cell reconstitution is sufficient for disease induction and whether targeted mast cell silencing can prevent neoangiogenesis and joint destruction, 2 hallmarks of rheumatoid arthritis.

METHODS

Ankle swelling and clinical index scores were determined after injection of either K/BxN mouse-derived serum or control serum in wild-type Kit(+)/Kit(+) mice, congenic mast cell-deficient Kit(W)/Kit(W-v) mice, or mast cell-deficient Kit(W)/Kit(W-v) mice reconstituted with mast cells, either by intraperitoneal or selective intraarticular injection. Angiogenesis was quantified in vivo by measuring activated alphavbeta3 integrin using (18)F-galacto-RGD and positron emission tomography. In addition, staining of joint tissue with hematoxylin and eosin, Giemsa, beta3, and alpha-actin was performed. The effect of mast cell stabilization by treatment with cromolyn or salbutamol was investigated in C57BL/6 or BALB/c mice.

RESULTS

Comparing wild-type mice, mast cell-deficient Kit(W)/Kit(W-v) mice, and mast cell-reconstituted Kit(W)/Kit(W-v) mice, we first showed that intraarticular and intraperitoneal mast cell engraftment fully restores susceptibility to antibody-induced arthritis, angiogenesis, and alphavbeta3 integrin activation. Importantly, selective mast cell silencing with either salbutamol or cromolyn prevented alphavbeta3 integrin activation, angiogenesis, and joint destruction.

CONCLUSION

Mast cell engraftment fully restores susceptibility to alphavbeta3 integrin activation, angiogenesis, and joint destruction in GPI antibody-induced arthritis. Importantly, selective mast cell stabilization prevents alphavbeta3 integrin activation, angiogenesis, and joint destruction.

Cercarial Dermatitis Caused by Bird Schistosomes Comprises Both Immediate and Late Phase Cutaneous Hypersensitivity Reactions

Avian schistosomes are the primary causative agent of cercarial dermatitis in humans, but despite its worldwide occurrence, little is known of the immune mechanism of this disease. Using a murine model, hosts were exposed to primary (1x) and multiple (4x) infections of Trichobilharzia regenti via the pinna. Penetration of larvae into the skin evoked immediate edema, thickening of the exposure site, and an influx of leukocytes, including neutrophils, macrophages, CD4+ lymphocytes, and mast cells. A large proportion of the latter were in the process of degranulating. After 1x infection, inflammation was accompanied by the release of IL-1beta, IL-6, and IL-12p40. In contrast, in 4x reinfected animals the production of histamine, IL-4, and IL-10 was dramatically elevated within 1 h of infection. Analysis of Ag-stimulated lymphocytes from the skin-draining lymph nodes revealed that cells from 1x infected mice produced a mixed Th1/Th2 cytokine response, including abundant IFN-gamma, whereas cells from 4x reinfected mice were Th2 polarized, dominated by IL-4 and IL-5. Serum Abs confirmed this polarization, with elevated levels of IgG1 and IgE after multiple infections. Infection with radiolabeled cercariae revealed that almost 90% of larvae remained in the skin, and the majority died within 8 days after infection, although parasites were cleared more rapidly in 4x reinfected mice. Our results are the first demonstration that cercarial dermatitis, caused by bird schistosomes, is characterized by an early type I hypersensitivity reaction and a late phase of cutaneous inflammation, both associated with a polarized Th2-type acquired immune response.

Critical role of mast cells in inflammatory diseases and the effect of acute stress

Mast cells are not only necessary for allergic reactions, but recent findings indicate that they are also involved in a variety of neuroinflammatory diseases, especially those worsened by stress. In these cases, mast cells appear to be activated through their Fc receptors by immunoglobulins other than IgE, as well as by anaphylatoxins, neuropeptides and cytokines to secrete mediators selectively without overt degranulation. These facts can help us better understand a variety of sterile inflammatory conditions, such as multiple sclerosis (MS), migraines, inflammatory arthritis, atopic dermatitis, coronary inflammation, interstitial cystitis and irritable bowel syndrome, in which mast cells are activated without allergic degranulation.

Serum Tryptase in Allergic Rhinitis: Effect of Cetirizine Treatment

Activated mast cells release a large range of potent mediators of allergic inflammation, including proteases. The tryptase serum levels were evaluated in 13 subjects suffering from allergic perennial rhinitis. Moreover, the effects of cetirizine treatment on serum tryptase were studied using the UniCap™ tryptase fluoroenzymeimmunoassay.

In allergic patients the serum tryptase values (M±SD: 6.1 ± 2.4 μg/L) were significantly (p < 0.02) higher than the values detected in controls (3.0 ± 1.2 μg/L). In allergic rhinitis, after antihistamine treatment, tryptase values (4.4 ± 1.8 μg/L) decreased significantly (p < 0.001). After two weeks from the cetirizine stop, the tryptase levels increased again (5.5 ± 2.6 μg/l).

The results demonstrate that mast cells are constantly activated in perennial allergic rhinitis. The antihistamine treatment is effective in reducing the tryptase release from mast cells, but the mechanism of action of cetirizine is still to understand.

Clinical and histological evaluation of an analogue of palmitoylethanolamide, PLR 120 (comicronized Palmidrol INN) in cats with eosinophilic granuloma and eosinophilic plaque: a pilot study

Fifteen cats with eosinophilic granuloma or eosinophilic plaque were given PLR 120 at the dosage of 10 mg kg-1 twice daily for one month. PLR-120 down-modulates mast cell degranulation via a receptor-mediated mechanism. No other drugs were permitted and cats were kept free of parasites throughout the study. A clinical evaluation and skin biopsies were performed before and after the treatment. Clinical improvement was assessed at 15 and 30 days. Mast cell numbers were counted and their granular content was assessed by densitometric analysis on toluidine blue-stained sections before and after the treatment. Ten of 15 (67%) cats showed clinical improvement of signs and lesions. There was no significant difference between mast cell numbers in skin biopsies taken before and after the trial, whereas the number of granules was significantly increased (P < 0.009). This pilot study suggests that PLR-120 might be a useful drug for the treatment of eosinophilic granuloma and eosinophilic plaque.

Characterization of the inflammatory infiltrate during IgE-mediated late phase reactions in the skin of normal and atopic dogs

In canine and human atopic patients, the intracutaneous injection of offending allergens is followed by the development of both immediate and late-phase reactions. The present study was performed to expand on the characterization and dynamics of inflammatory cell subsets during IgE-mediated late-phase reactions in canine skin. Three normal dogs and three Dermatophagoides farinae-allergic dogs were selected for this experiment. All dogs were challenged intradermally with mite allergen, purified anticanine IgE antibodies (positive control) or phosphate-buffered saline (negative control). Skin biopsies were obtained before and 6, 12 and 24 h post-injection. Sections were stained with metachromatic and eosinophil-specific histological stains. Additionally, we used an immunohistochemical method with antibodies specific for canine leukocyte antigens. This study confirmed the occurrence of a late-phase reaction in atopic skin following allergen challenge, and in normal and atopic canine skin after intradermal injection of IgE-specific antibodies. Whereas early emigrating dermal cells were composed chiefly of neutrophil and activated eosinophil granulocytes, there was an influx of alpha beta T-lymphocytes and dermal dendritic cells in later stages of the late-phase reactions. Because IgE-mediated late-phase reactions resemble spontaneous atopic canine skin lesions, both at macroscopic and microscopic levels, we propose the use of similar challenges to study the anti-inflammatory effects of anti-allergic drugs in a pre-clinical setting.

Basophil responses to chemokines are regulated by both sequential and cooperative receptor signaling

To investigate human basophil responses to chemokines, we have developed a sensitive assay that uses flow cytometry to measure leukocyte shape change as a marker of cell responsiveness. PBMC were isolated from the blood of volunteers. Basophils were identified as a single population of cells that stained positive for IL-3Ralpha (CDw123) and negative for HLA-DR, and their increase in forward scatter (as a result of cell shape change) in response to chemokines was measured. Shape change responses of basophils to chemokines were highly reproducible, with a rank order of potency: monocyte chemoattractant protein (MCP) 4 (peak at <1 nM) >/= eotaxin-2 = eotaxin-3 >/= eotaxin > MCP-1 = MCP-3 > macrophage-inflammatory protein-1alpha > RANTES = MCP-2 = IL-8. The CCR4-selective ligand macrophage-derived chemokine did not elicit a response at concentrations up to 10 nM. Blocking mAbs to CCR2 and CCR3 demonstrated that responses to higher concentrations (>10 nM) of MCP-1 were mediated by CCR3 rather than CCR2, whereas MCP-4 exhibited a biphasic response consistent with sequential activation of CCR3 at lower concentrations and CCR2 at 10 nM MCP-4 and above. In contrast, responses to MCP-3 were blocked only in the presence of both mAbs, but not after pretreatment with either anti-CCR2 or anti-CCR3 mAb alone. These patterns of receptor usage were different from those seen for eosinophils and monocytes. We suggest that cooperation between CCRs might be a mechanism for preferential recruitment of basophils, as occurs in tissue hypersensitivity responses in vivo.

Phagocytic and tumor necrosis factor alpha response of human mast cells following exposure to gram-negative and gram-positive bacteria

Recent studies have implicated rodent mast cells in the innate immune response to infectious bacteria. We report that cord blood-derived human mast cells (CBHMC) obtained from culture of cord blood progenitors phagocytozed and killed various gram-negative and gram-positive bacteria and simultaneously released considerable amounts of tumor necrosis factor alpha. Overall, the extent of the endocytic and exocytic response of CBHMC correlated with the number of adherent bacteria. Thus, human mast cells are intrinsically capable of mediating microbial recognition and of actively contributing to the host defense against bacteria.

Immunopharmacology of human mast cells and basophils

Human mast cells and basophils play a key role in the pathogenesis of several immunological and inflammatory disorders, not only by producing inflammatory and fibrogenic mediators, but also by directly (CD40 ligand) and indirectly secreting various cytokines and chemokines. Studies carried out to evaluate the effects of drugs that modulate the release of mediators and cytokines from these cells have contributed to clarifying the biochemical mechanism by which immunological and non-immunological stimuli activate these cells. Significant differences have been documented between human mast cells and basophils as regard the pharmacological agents that modulate the release of mediators, between mast cells isolated from different anatomical sites, and between compounds of the same class of drugs. Efforts to gain insight into the biochemical events occurring during immunological activation of mast cells and basophils could lead to the identification of new biochemical targets for therapeutic interventions in several immunological disorders.

Milestones in the biology and pharmacology of H1-receptor antagonists

Daniele Bovet's pioneering discovery that a series of compounds possessing anti-histamine activity reduced the symptoms of anaphylaxis provided the proof that histamine plays a pivotal role as a mediator of allergic reactions. Basophils and mast cells are the major sources of histamine in man and they are thus one of the primary effector cells of allergic inflammation. Some H1-receptor antagonists possess a variety of antiinflammatory activity to H1 antagonism in vitro and in vivo. This promising area should be explored further and much remains to be done in the evaluation of the immunomodulatory effects of anti-histamines.