The human basophil: a new appreciation of its role in immune responses

Human basophils and eosinophils are the direct target leukocytes of the novel IL-1 family member IL-33

In mice, interleukin-18 (IL-18) regulates Th1- or Th2-type immune responses depending on the cytokine environment and effector cells involved, and the ST2-ligand, IL-33, primarily promotes an allergic phenotype. Human basophils, major players in allergic inflammation, constitutively express IL-18 receptors, while ST2 surface expression is inducible by IL-3. Unexpectedly, freshly isolated basophils are strongly activated by IL-33, but, in contrast to mouse basophils, do not respond to IL-18. IL-33 promotes IL-4, IL-13 and IL-8 secretion in synergy with IL-3 and/or FcepsilonRI-activation, and enhances FcepsilonRI-induced mediator release. These effects are similar to that of IL-3, but the signaling pathways engaged are distinct because IL-33 strongly activates NF-kappaB and shows a preference for p38 MAP-kinase, while IL-3 acts through Jak/Stat and preferentially activates ERK. Eosinophils are the only other leukocyte-type directly activated by IL-33, as evidenced by screening of p38-activation in peripheral blood cells. Only upon CD3/CD28-ligation, IL-33 weakly enhances Th2 cytokine expression by in vivo polarized Th2 cells. This study on primary human cells demonstrates that basophils and eosinophils are the only direct target leukocytes for IL-33, suggesting that IL-33 promotes allergic inflammation and Th2 polarization mainly by the selective activation of these specialized cells of the innate immune system.

Effects of a new nutraceutical ingredient on allergen-induced sulphidoleukotrienes production and CD63 expression in allergic subjects

Allergic diseases represent conditions affecting millions of individuals across the world. The objective of this study was to investigate the potential anti-allergic effects of a new nutraceutical ingredient, Pantescal (Bionap, Italy), contained in different food supplements. Pantescal is a mixture of plant extracts, such as Capparis spinosa, Olea europaea, Panax Ginseng and Ribes nigrum. The study was a randomized, double-blind, placebo controlled design. 60 patients allergic to common aeroallergens were chosen. Allergic patients were divided into two groups: one group was supplemented by Pantescal and the other, using a placebo formulation. Two in vitro tests were performed on blood samples taken from patients before and at 2 h, 2, 3 and 10 days after supplementation: cellular antigen stimulation test (CAST) was used to analyze the amount of sulphidoleukotrienes (SLT) production and flow-cytometric antigen stimulation test (FAST) to measure expression of basophil degranulation marker (CD63) was also performed. CAST showed that after 2 and 3 days, a slight decrease of SLT production was evident but only after 10 days did it become significant with a percentage of inhibition (P.I)=43.3%. FAST revealed that there were no statistical differences for the first 2 days after supplementation although there was an inhibitory trend in the supplemented patients. CD63 expression was significantly reduced after 10 days (P.I.=64.8%). This study suggests that Pantescal is effective in reducing allergic biomarkers such as CD63 protein and SLT in atopic subjects. The higher inhibitory effect on CD63 expression compared to SLT production allows us to hypothesize cell membrane stabilization as the main potential mechanism to explain the observed Pantescal protective effects.

IL-33 amplifies both Th1- and Th2-type responses through its activity on human basophils, allergen-reactive Th2 cells, iNKT and NK cells

IL-33 is an IL-1 family member recently identified as the ligand for T1/ST2 (ST2), a member of the IL-1 receptor family. ST2 is stably expressed on mast cells and T(h)2 effector T cells and its function has been studied in the context of T(h)2-associated inflammation. Indeed, IL-33 induces T(h)2 cytokines from mast cells and polarized mouse T cells and leads to pulmonary and mucosal T(h)2 inflammation when administered in vivo. To better understand how this pathway modulates inflammatory responses, we examined the activity of IL-33 on a variety of human immune cells. Human blood-derived basophils expressed high levels of ST2 receptor and responded to IL-33 by producing several pro-inflammatory cytokines including IL-1 beta, IL-4, IL-5, IL-6, IL-8, IL-13 and granulocyte macrophage colony-stimulating factor. Next, utilizing a human T(h)2-polarized T cell culture system derived from allergic donor blood cells, we found that IL-33 was able to enhance antigen-dependent and -independent T cell responses, including IL-5, IL-13 and IFN-gamma production. IL-33 activity was also tested on V alpha 24-positive human invariant NKT (iNKT) cells. In the presence of alpha-galactosylceramide antigen presentation, IL-33 dose dependently enhanced iNKT production of several cytokines, including both IL-4 and IFN-gamma. IL-33 also directly induced IFN-gamma production from both iNKT and human NK cells via cooperation with IL-12. Taken together, these results indicate that in addition to its activity on human mast cells, IL-33 is capable of activating human basophils, polarized T cells, iNKT and NK cells. Moreover, the nature of the responses elicited by IL-33 suggests that this axis may amplify both T(h)1- and T(h)2-oriented immune responses.

The effects of dasatinib on IgE receptor-dependent activation and histamine release in human basophils

Dasatinib is a multitargeted drug that blocks several tyrosine kinases. Apart from its well-known antileukemic activity, the drug has attracted attention because of potential immunosuppressive and anti-inflammatory effects. We report that dasatinib at 1 microM completely blocks anti-IgE-induced histamine release in blood basophils in healthy donors, and allergen-induced release of histamine in sensitized individuals. In addition, dasatinib inhibited FcepsilonRI-mediated release of IL-4 and IgE-mediated up-regulation of CD13, CD63, CD164, and CD203c in basophils. The effects of dasatinib were dose-dependent (IC(50): 50-500 nM) and specific for FcepsilonRI activation in that the drug failed to inhibit C5a-induced or Ca-ionophore-induced histamine release. Interestingly, at lower concentrations, dasatinib even promoted FcepsilonRI-dependent histamine release in basophils in allergic subjects. In consecutive studies, dasatinib was found to interact with and block several FcepsilonRI downstream targets in basophils, including Btk. Correspondingly, FcepsilonRI-mediated histamine secretion in basophils was markedly reduced in Btk knockout mice and in a patient with Btk deficiency. However, the remaining "low-level" mediator secretion in Btk-deficient cells was fully blocked down again by 1 muM dasatinib. Together, these data suggest that dasatinib inhibits FcepsilonRI-mediated activation of basophils through multiple signaling molecules including Btk. Dasatinib may be an interesting agent for immunologic disorders involving Btk-dependent responses or/and FcepsilonRI activation of basophils.

Recombinant Allergens Promote Expression of Aminopeptidase-N (CD13) on Basophils in Allergic Patients

IgE-dependent activation of basophils is associated with upregulation of several surface molecules. We recently identified the surface enzyme aminopeptidase N (CD13) as a novel activation antigen on human basophils. In the present study, we asked whether CD13 can be employed as a novel marker of allergen-induced activation of basophils in allergic individuals. Patients allergic to major allergens from grass pollen (Phl p 1, Phl p 5), birch pollen (Bet v 1), or house dust mites (Der p 2), were examined. Blood basophils were exposed to various concentrations of recombinant allergens for 15 minutes, and examined for expression of CD13 by multicolor flow cytometry. The allergen-induced upregulation of CD13 was compared with allergen-dependent increases in expression of CD63 and CD203c. Exposure to recombinant allergens resulted in an increase in expression of CD13 on basophils in all sensitized individuals, whereas no increase in CD13 was seen in healthy controls. The effects of the recombinant allergens on CD13-expression were dose- and time-dependent, were not observed in the absence of extracellular calcium, and were counteracted by preincubation of basophils with the PI3-kinase-targeting drugs staurosporin and LY294002. There was a good correlation between allergen-induced upregulation of CD13, CD63, and CD203c on basophils. In aggregate, our data show that recombinant allergens promote expression of CD13 on basophils in sensitized individuals. The functional significance and diagnostic implications of this observation remain to be determined.

Mast cells and basophils are selectively activated in vitro and in vivo through CD200R3 in an IgE-independent manner

Mast cells and basophils have been implicated in the host defense system against pathogens and in the development of allergic disorders. Although IgE-dependent responses via FcepsilonRI on these cells have been extensively studied, little is known about cell surface molecules that are selectively expressed by these cells and engaged in their activation via an IgE-independent mechanism. We have recently established two mAbs that reacted specifically with murine mast cells and basophils, and one of them selectively depleted basophils when administered in vivo. Biochemical and flow cytometric analyses revealed that both mAbs specifically recognized a CD200R-like protein, CD200R3, but not other CD200R family members. CD200R3 existed as a disulfide-linked dimer, unlike other CD200Rs, and was expressed on mast cells and basophils primarily in association with an ITAM-bearing adaptor DAP12. Cross-linking of CD200R3 with the mAbs induced degranulation in mast cells and production of the cytokine IL-4 in basophils in vitro. Administration of the nondepleting mAb in vivo elicited systemic and local anaphylaxis in a CD200R3-dependent manner. These results suggest that CD200R3 functions as an activating receptor on mast cells and basophils to regulate IgE-independent immune responses in cooperation with an inhibitory receptor CD200R, similar to the paired receptors expressed on NK cells.

Influence of intestinal cestodes on the blood picture of the brown rats (Rattus norvegicus) of Hyderabad Sindh, Pakistan

Present study was performed to determined the changes in the blood picture of the brown rats Rattus norvegicus naturally infected with intestinal cestodes. The results are based on the examination of 82 brown rats captured at random from Hyderabad city and its adjacent areas. Blood profiling of cestode (Hymenolepis diminuta and Hymenolepis nana) infected male and female rats showed significantly lower values of Total Erythrocyte Count (TEC), Haemoglobin (Hb) concentration, Haematocrit (Hct), Mean Corpuscular Haemoglobin (MCH) and Mean Corpuscular Haemoglobin Concentration (MCHC) as compared to their control (non-infected) rats of both sexes. The Mean Corpuscular Volume (MCV) value for infected male and female rats was found significantly higher than those of their control rats. A significantly higher Total Leukocyte Count (TLC) in male and female infected rats was noted as against the non-infected (control) rats of both sexes. The Differential Leukocyte Count (DLC) revealed significant increase in absolute number of each type of cell in cestode infected male and female rats. However, lymphocyte and basophil counts recorded from male infected rats were similar to the counts of their control rats. Conspicuous changes in the blood picture of cestode infected male and female rats indicate host-parasite interaction as well as the triggering of defense mechanism in the host against infection.

A comparison of inflammatory mediators released by basophils of asthmatic and control subjects in response to high-affinity IgE receptor aggregation

BACKGROUND

In human blood basophils, cross-linking the high-affinity IgE receptor Fc epsilonRI with multivalent antigen activates a signaling pathway leading to secretion of inflammatory mediators and cytokine production. Basophils are known to play an important role in the pathogenesis of asthma but there has been no comprehensive examination of the effectors these cells produce. Here a study of the transcription and release of a selection of chemokines and cytokines from basophils was undertaken.

METHODS

A Cartesian antibody array provided an effective method of assaying for multiple cytokines and chemokines simultaneously. Results were verified by RT-PCR and ELISA assays. This allowed the comparison of freshly prepared peripheral blood basophil responses to cross-linking of the high-affinity IgE receptor, with and without preincubation with IL-3.

RESULTS

Evidence that human blood basophils produce the chemokines MIP-5, eotaxin and GM-CSF was provided by antibody array and RT-PCR analyses. Preincubation with IL-3 enhanced the expression and release of IL-13, IL-8 and mRNA transcripts encoding MIP-5 and GATA2 in basophils from both asthmatic and control subjects. Leptin mRNA transcription, storage and release in basophils are described for the first time.

CONCLUSIONS

Surveying cytokine and chemokines stored and released by peripheral blood basophils shows that asthmatic and control subjects share similar profiles even when their degranulation responses are distinct. Evidence is provided for the production of leptin, GM-CSF, eotaxin and MIP-5 by peripheral blood basophils. IL-3 preincubation enhances the production and release of IL-8 upon IgE receptor cross-linking.

Interleukin-3 promotes the expression of E-NPP3/CD203C on human blood basophils in healthy subjects and in patients with birch pollen allergy

We recently identified the ectoenzyme CD203c as a novel basophil activation antigen that is upregulated in response to FcepsilonRI cross-linkage. We investigated the effects of various interleukins (ILs) on expression of CD203c on blood basophils using an antibody against CD203c and flow cytometry. Of all cytokines tested, only IL-3 was found to upregulate expression of CD203c on basophils above baseline levels. The effects of IL-3 were dose- and time-dependent (EC(50): 0.1-1 ng/ml) without differences observed between healthy and allergic donors. Whereas anti-IgE induced maximum upregulation of CD203c within 15 minutes, the IL-3-induced upregulation showed a maximum after 180 minutes. IgE-receptor cross-linking resulted in enhanced expression of both CD63 and CD203c, whereas IL-3 enhanced the levels of CD203c without promoting expression of CD63. The IL-3-induced upregulation of CD203c was also observed in highly enriched basophils and was counteracted by a blocking antibody against the alpha chain of the IL-3 receptor (CD123). The IL-3-induced upregulation of CD203c was also found to depend on the presence of calcium. To analyze signaling pathways involved in IL-3-induced upregulation of CD203c, pharmacologic inhibitors were applied. The PI3-kinase inhibitors, wortmannin and LY294002 counteracted the IL-3-induced expression of CD203c, whereas MEK- and PKC inhibitors showed no effects. In conclusion, IL-3 upregulates expression of CD203c on basophils through a specific receptor and via a PI3-kinase-dependent signaling-pathway. Compared to FcepsilonRI-mediated cell activation, IL-3-induced upregulation of CD203c is a late(r) event and is not accompanied by upregulation of CD63.

Flavonoids and related compounds as anti-allergic substances

The prevalence of allergic diseases has increased all over the world during the last two decades. Dietary change is considered to be one of the environmental factors that cause this increase and worsen allergic symptoms. If this is the case, an appropriate intake of foods or beverages with anti-allergic activities is expected to prevent the onset of allergic diseases and ameliorate allergic symptoms. Flavonoids, ubiquitously present in vegetables, fruits or teas possess anti-allergic activities. Flavonoids inhibit histamine release, synthesis of IL-4 and IL-13 and CD40 ligand expression by basophils. Analyses of structure-activity relationships of 45 flavones, flavonols and their related compounds showed that luteolin, ayanin, apigenin and fisetin were the strongest inhibitors of IL-4 production with an IC(50) value of 2-5 microM and determined a fundamental structure for the inhibitory activity. The inhibitory activity of flavonoids on IL-4 and CD40 ligand expression was possibly mediated through their inhibitory action on activation of nuclear factors of activated T cells and AP-1. Administration of flavonoids into atopic dermatitis-prone mice showed a preventative and ameliorative effect. Recent epidemiological studies reported that a low incidence of asthma was significantly observed in a population with a high intake of flavonoids. Thus, this evidence will be helpful for the development of low molecular compounds for allergic diseases and it is expected that a dietary menu including an appropriate intake of flavonoids may provide a form of complementary and alternative medicine and a preventative strategy for allergic diseases. Clinical studies to verify these points are now in progress.

Polyspecific organic cation transporters: structure, function, physiological roles, and biopharmaceutical implications

The body is equipped with broad-specificity transporters for the excretion and distribution of endogeneous organic cations and for the uptake, elimination and distribution of cationic drugs, toxins and environmental waste products. This group of transporters consists of the electrogenic cation transporters OCT1-3 (SLC22A1-3), the cation and carnitine transporters OCTN1 (SLC22A4), OCTN2 (SLC22A5) and OCT6 (SLC22A16), and the proton/cation antiporters MATE1, MATE2-K and MATE2-B. The transporters show broadly overlapping sites of expression in many tissues such as small intestine, liver, kidney, heart, skeletal muscle, placenta, lung, brain, cells of the immune system, and tumors. In epithelial cells they may be located in the basolateral or luminal membranes. Transcellular cation movement in small intestine, kidney and liver is mediated by the combined action of electrogenic OCT-type uptake systems and MATE-type efflux transporters that operate as cation/proton antiporters. Recent data showed that OCT-type transporters participate in the regulation of extracellular concentrations of neurotransmitters in brain, mediate the release of acetylcholine in non-neuronal cholinergic reactions, and are critically involved in the regulation of histamine release from basophils. The recent identification of polymorphisms in human OCTs and OCTNs allows the identification of patients with an increased risk for adverse drug reactions. Transport studies with expressed OCTs will help to optimize pharmacokinetics during development of new drugs.

Basophils are essential initiators of a novel type of chronic allergic inflammation

Basophils represent less than 1% of peripheral blood leukocytes and have often been considered as minor and possibly redundant circulating mast cells. The recent finding that basophils readily generate large quantities of T helper 2 (Th2) cytokines such as IL-4 provided new insights into the possible role of basophils in allergic disorders and immunity to pathogens. However, in-depth studies on basophils, particularly their functions in vivo, have been hampered by the lack of appropriate animal models, such as mutant animals deficient only in basophils. Here, we established a mAb that reacted with mouse basophils and depleted them when administered in vivo. The mAb treatment of mice did not show any significant effect on classical allergic reactions such as passive cutaneous anaphylaxis and contact hypersensitivity. In contrast, it completely abolished the development of IgE-mediated chronic allergic dermatitis that is characterized by massive eosinophil infiltration, even though basophils accounted for only approximately 2% of the infiltrates. The treatment during the progression of the dermatitis resulted in drastic reduction in numbers of infiltrating eosinophils and neutrophils, concomitantly with elimination of basophils from the skin lesions. Thus, basophils play a pivotal role in the development of IgE-mediated chronic allergic inflammation, as an initiator rather than as an effector.

De novo CD5+ diffuse large B cell lymphoma with basophilia in the peripheral blood: successful treatment with autologous peripheral blood stem cell transplantation

Basophils play an important role in allergic inflammation and are pathologically related to hematological disturbances, such as iron deficiency anemia and myeloproliferative disorders; however, they are only rarely encountered in lymphoid malignancies. Here, we report the case of a 33-year-old man with a bulky mass of the small intestine, multiple paraaortic lymphoadenopathy, pleural effusion, and ascites, who was diagnosed as a case of de novo CD5+ diffuse large B cell lymphoma (DLBCL). This patient showed a marked elevation of the basophil count in the peripheral blood, which appeared to run in parallel with the tumor burden. High dose chemotherapy followed by autologous peripheral blood cell transplantation yielded complete remission, and the patient has remained disease free for 5 years. To the best of our knowledge, this is the first report of a case of de novo CD5+ DLBCL showing marked elevation of the PB basophil count.

The 21st century renaissance of the basophil? Current insights into its role in allergic responses and innate immunity

Basophils and mast cells express all the three subchains of the high-affinity immunoglobulin E (IgE) receptor Fc epsilon RI and contain preformed histamine in the cytoplasmic granules. However, it is increasingly clear that these cells play distinct roles in allergic inflammatory disease. Despite their presence throughout much of the animal kingdom, the physiological function of basophils remains obscure. As rodent mast cells are more numerous than basophils, and generate an assortment of inflammatory cytokines, basophils have often been regarded as minor players in allergic inflammation. In humans, however, basophils are the prime early producers of interleukin (IL)-4 and IL-13, T helper (Th)2-type cytokines crucial for initiating and maintaining allergic responses. Basophils also express CD40 ligand which, in combination with IL-4 and IL-13, facilitates IgE class switching in B cells. They are the main cellular source for early IL-4 production, which is vital for the development of Th2 responses. The localization of basophils in various tissues affected by allergic inflammation has now been clearly demonstrated by using specific staining techniques and the new research is shedding light on their selective recruitment to the tissues. Finally, recent studies have shown that basophil activation is not restricted to antigen-specific IgE crosslinking, but can be caused in non-sensitized individuals by a growing list of parasitic antigens, lectins and viral superantigens, binding to non-specific IgE antibodies. This, together with novel IgE-independent routes of activation, imparts important new insights into the potential role of basophils in both adaptive and innate immunity.

Granzyme B, a novel mediator of allergic inflammation: its induction and release in blood basophils and human asthma

Histamine, leukotriene C4, IL-4, and IL-13 are major mediators of allergy and asthma. They are all formed by basophils and are released in particularly large quantities after stimulation with IL-3. Here we show that supernatants of activated mast cells or IL-3 qualitatively change the makeup of granules of human basophils by inducing de novo synthesis of granzyme B (GzmB), without induction of other granule proteins expressed by cytotoxic lymphocytes (granzyme A, perforin). This bioactivity of IL-3 is not shared by other cytokines known to regulate the function of basophils or lymphocytes. The IL-3 effect is restricted to basophil granulocytes as no constitutive or inducible expression of GzmB is detected in eosinophils or neutrophils. GzmB is induced within 6 to 24 hours, sorted into the granule compartment, and released by exocytosis upon IgE-dependent and -independent activation. In vitro, there is a close parallelism between GzmB, IL-13, and leukotriene C4 production. In vivo, granzyme B, but not the lymphoid granule marker granzyme A, is released 18 hours after allergen challenge of asthmatic patients in strong correlation with interleukin-13. Our study demonstrates an unexpected plasticity of the granule composition of mature basophils and suggests a role of granzyme B as a novel mediator of allergic diseases.

When is a mouse basophil not a basophil?

The identification and characterization of mouse basophils have historically been hampered by the extreme rarity of this cell type. Virtually no photomicrographs of hematologically stained (eg, Wright-Giemsa) examples of mouse basophils exist in the literature. However, 4 recent studies in the past 2 years have used flow cytometry and a defined set of cell-surface markers to identify and subsequently isolate mouse "basophils," including the publication of stained cytospin preparations of these cells. Surprisingly, a reevaluation of the data from all 4 of the studies revealed several issues of concern that suggest that the cells under study are not necessarily basophils. Nonetheless, we propose that these studies do provide the foundation for a reevaluation of the defining characteristics of a basophil and/or provide support for the provocative conclusion that a new previously overlooked leukocyte subtype has been identified. The purpose of this commentary is to revisit these previously published studies, highlight the relevant issues, and provide a different perspective in the hope of developing a consensus within the research community as to the true identity of the "basophils" described in these studies.

Isolation of transcriptionally active umbilical cord blood-derived basophils expressing Fc epsilon RI, HLA-DR and CD203c

BACKGROUND

Basophils are inflammatory cells associated with allergy and parasite infections. Investigation of their true biological function has long been hampered by the difficulty in obtaining sufficient amounts of pure basophils and by the lack of phenotypic markers. Moreover, it has been very difficult to clone and identify basophil-specific granule proteins, partially because of an almost complete lack of mRNA in mature circulating basophils.

METHODS

To obtain transcriptionally active immature basophils, umbilical cord blood cells were cultured in the presence of interleukin (IL)-3. The cells were analysed by flow cytometry and by histological staining.

RESULTS

The continuous presence of IL-3 in cord blood cultures resulted in the expansion of basophil precursors co-expressing FcepsilonRI and the recently described mast cell/basophil marker, 97A6 (CD203c). Several nonbasophil markers (i.e. CD3, CD14, CD15, CD16, CD19 and CD21) were absent on the cultured basophils. However, we show that in early cultures, almost 60% of the CD203c+ cells co-express human leukocyte antigen (HLA)-DR, a marker that is absent on mature circulating basophils. The presence of HLA-DR on basophil precursors may explain the low recovery (24+/-5.2%) obtained after isolation of cultured basophils, when using a conventional basophil isolation kit that removes HLA-DR+ cells. A novel purification method was developed, including a two-step cocktail of antibodies against selected markers, which resulted in both high purity (95+/-0.5%) and recovery (59+/-1.5%) of cultured basophils.

CONCLUSIONS

We here establish cord blood cultures as a source from which transcriptionally active basophil precursors can be isolated in reasonable quantities for thorough biochemical characterization.

Serum-induced basophil CD63 expression by means of a tricolour flow cytometric method for the in vitro diagnosis of chronic urticaria

BACKGROUND

Functional autoantibodies against the alpha-chain of the high-affinity IgE receptor (FcepsilonRIalpha) identify a subset of patients with chronic urticaria (CU) due to autoreactivity, as assessed by an in vivo positive response to autologous serum skin test (ASST). We performed a study to standardize the serum-induced basophil activation assay by flow cytometry (FCM) using a new tricolour method, assessing the diagnostic performance of this test in discriminating between ASST+ and ASST- CU patients.

METHODS

Sera of 64 CU patients (22 ASST+ CU and 42 ASST- CU) and 10 healthy subjects were tested for their ability to induce basophil CD63 expression when incubated with whole blood of both atopic (DA) and non-atopic donors (DNA). Using a triple-labelled strategy with anti-CD123, anti-HLA-DR and anti-CD63 antibodies, CD63+ basophils were identified on a selected population of CD123+ HLA-DR- cells. In 3 ASST+ CU patients who underwent cyclosporine therapy, the assay was performed before and after treatment.

RESULTS

The ASST+ CU sera resulted in a significant higher induction of basophil CD63 expression compared with ASST- CU and healthy donors sera; when whole blood from DA was used, sensitivity and specificity of the assay were 95.5% and 90.5% respectively. ASST+ CU serum activity was significantly decreased during cyclosporine A treatment, in parallel with clinical remission.

CONCLUSIONS

Chronic urticaria serum-induced CD63 expression assay performed on DA whole blood by means of our tricolour FCM method could be the most useful tool for identification of a subset of patients with autoimmune CU and may become a promising tool also for monitoring treatment efficacy.

Identification of basophils by a mAb directed against pro-major basic protein 1

BACKGROUND

Basophils possess characteristics of both mast cells and eosinophils, and all 3 cell types often are found together, particularly during allergic reactions. A mAb (J175-7D4) generated against the recombinant pro-form of human eosinophil granule major basic protein 1 (rproMBP1) appeared to stain only basophils in tissue specimens.

OBJECTIVE

We investigated J175-7D4 to characterize its specificity for basophils.

METHODS

Fluid-phase immunoprecipitation, Western blotting, and immunocytochemistry and immunohistochemistry were used to establish the specificity of J175-7D4.

RESULTS

First, J175-7D4 binds to various glycosylated and proteolytically processed forms of rproMBP1, but not to major basic protein. Second, cells transfected with the rproMBP1 gene and human placental tissue (known to express the pro-form of major basic protein 1 [proMBP1]) stain specifically with J175-7D4. In contrast, although mature eosinophils contain substantial major basic protein, they lack proMBP1 and do not stain. Neutrophils, lymphocytes, monocytes, and skin mast cells also are not stained. However, blood basophils are stained by J175-7D4, anti-IgE, Wright-Giemsa (metachromatically), and a previously characterized basophil-specific mAb, 2D7. Finally, formaldehyde-fixed, paraffin-embedded basophils are identically detected by J175-7D4 and 2D7, and J175-7D4 also recognizes putative basophils in formaldehyde-fixed, paraffin-embedded tissue specimens from inflammatory dermatoses, such as atopic dermatitis and delayed pressure urticaria.

CONCLUSION

The J175-7D4 mAb recognizes proMBP1 as a novel marker for human basophils. J175-7D4 should prove useful for characterizing basophil involvement in human health and disease.

Organic extracts of urban aerosol (< or =PM2.5) enhance rBet v 1-induced upregulation of CD63 in basophils from birch pollen-allergic individuals

Epidemiological studies have linked the high prevalence rates of IgE-mediated allergic diseases to an increase in exposure to traffic-related air pollutants such as diesel exhaust particles (DEPs). There is growing experimental evidence that organic compounds of DEPs, predominantly polycyclic aromatic hydrocarbons (PAHs), participate in the development and maintenance of allergic airway diseases. In this study we investigated the impact of organic extracts of urban aerosol (AERex) containing various PAH concentrations on the activation of human basophils. Whole blood samples from six birch pollen-allergic and five control subjects were repeatedly incubated in the presence of AERex with or without recombinant Bet v 1 (rBet v 1). Basophils were analyzed for CD63 expression as a measure of basophil activation by using multiparameter flow cytometry. Basophils, when exposed in vitro to AERex and rBet v 1, expressed CD63 significantly more than with antigen activation alone. AERex synergized with rBet v 1 in a dose-dependent manner, but did not activate basophils from nonallergic donors. AERex effect on CD63 upregulation was found in blood samples of all patients and did not occur in the absence of rBet v 1. Strongest basophil activation was monitored upon stimulation with AERex comprising the highest PAH content. The capability of AERex to increase activation of basophils from birch pollen-allergic subjects at ambient concentrations suggests an important role of organic compounds of airborne particles in the aggravation of IgE-mediated allergic diseases. This could be a new aspect of regulation of unspecific promoting stimuli in clinical manifestation of allergic inflammation.

Luteolin, a flavonoid, inhibits AP-1 activation by basophils

Flavonoids including luteolin, apigenin, and fisetin are inhibitors of IL-4 synthesis and CD40 ligand expression by basophils. This study was done to search for compounds with greater inhibitory activity of IL-4 expression and to clarify the molecular mechanisms through which flavonoids inhibit their expression. Of the 37 flavonoids and related compounds examined, ayanin, luteolin, and apigenin were the strongest inhibitors of IL-4 production by purified basophils in response to anti-IgE antibody plus IL-3. Luteolin did not suppress Syk or Lyn phosphorylation in basophils, nor did suppress p54/46 SAPK/JNK, p38 MAPK, and p44/42 MAPK activation by a basophilic cell line, KU812 cells, stimulated with A23187 and PMA. However, luteolin did inhibit phosphorylation of c-Jun and DNA binding activity of AP-1 in nuclear lysates from stimulated KU812 cells. These results provide a fundamental structure of flavonoids for IL-4 inhibition and demonstrate a novel action of flavonoids that suppresses the activation of AP-1.

Developmental checkpoints of the basophil/mast cell lineages in adult murine hematopoiesis

Basophils and mast cells, which are selectively endowed with the high-affinity IgE receptor and mediate a range of adaptive and innate immune responses, have an unknown developmental relationship. Here, by evaluating the expression of the beta7 integrin, a molecule that is required for selective homing of mast cell progenitors (MCPs) to the periphery, we identified bipotent progenitors that are capable of differentiating into either cell type in the mouse spleen. These basophil/mast cell progenitors (BMCPs) gave rise to basophils and mast cells at the single-cell level and reconstituted both mucosal and connective tissue mast cells. We also identified the basophil progenitor (BaP) and the MCP in the bone marrow and the gastrointestinal mucosa, respectively. We further show that the granulocyte-related transcription factor CCAAT/enhancer-binding protein alpha (C/EBPalpha) plays a primary role in the fate decision of BMCPs, being expressed in BaPs but not in MCPs. Thus, circulating basophils and tissue mast cells share a common developmental stage at which their fate decision might be controlled principally by C/EBPalpha.

Cytotoxic T lymphocyte exocytosis: bring on the SNAREs!

Despite our general understanding of membrane traffic, the molecular machinery at the immunological synapse (IS) that regulates exocytosis of lytic granules from cytotoxic T lymphocytes (CTLs) remains elusive. The identification of disease-causing mutations in the small GTPase Rab27a, priming factor Munc13-4 and fusion protein syntaxin11 has defined an important role for these proteins in CTL exocytosis. In addition, the demonstration of a direct interaction in vitro between Rab27a and Munc13-4 suggests the possibility that the Rab27a-Munc13-4 cascade might regulate CTL exocytosis by engaging SNAREs such as syntaxin11. We propose that these SNAREs are likely to mediate the fusion of lytic granules with the plasma membrane of the IS.

Flowcytometric analysis of basophil counts in human blood and inaccuracy of hematology analyzers

BACKGROUND

Differential leukocyte counts are of proven clinical value, but information about basophil counts in normal and disease conditions is scarce although basophils are regarded as key effector cells in allergy.

AIMS

To establish and validate flowcytometric methods for counting basophils in peripheral human blood, to determine reference values, and to examine the accuracy of two widely used hematology analyzers.

METHODS

Basophils were measured in whole blood by flowcytometry after staining with antibodies against the IL-3-receptor (CD123) or the eotaxin-receptor (CCR3) combined with other markers used for gating or validation purposes.

RESULTS

The basophil percentages in 95 healthy adults showed an excellent correlation between the two independent flowcytometric methods, demonstrating that both are accurate and precise. The most robust maker is CCR3, which seems to be sufficient to specifically identify basophils. Normal values of relative and absolute blood basophils counts were 0.22-1.28% and 0.014-0.087 G/L (95% reference intervals), respectively. Basophil counts measured with two hematology analyzers Coulter GEN-S and ADVIA-120 showed no correlation between these instruments. Comparing the data obtained by flowcytometry and the analyzers demonstrate that basophil counts of the GEN-S are erratic, while the ADVIA-120 gives at least an estimation of true basophil numbers.

CONCLUSIONS

We provide a solid description and validation of a novel and rapid method for the flowcytometric enumeration of basophil in whole blood. The fact that the most heavily used Hematology autoanalyzer gives completely erroneous results could explain why basophils counts have not yet received recognition as a clinically useful diagnostic marker.

Basophils play a critical role in the development of IgE-mediated chronic allergic inflammation independently of T cells and mast cells

The recruitment of basophils into the sites of allergic inflammation is often observed. However, no definitive evidence has been provided that basophils are crucially involved in the pathogenesis of chronic allergic disorders. Here, we show that basophils are responsible for the development of IgE-mediated chronic allergic inflammation independently of T cells and mast cells. A single subcutaneous injection of multivalent antigens elicited not only immediate- and late-phase ear swelling but also delayed-onset ear swelling with massive eosinophil infiltration in mice sensitized with antigen-specific IgE. Mast cells were essential for the immediate- and late-phase ear swelling but dispensable for the delayed one. T cells were also dispensable for the latter. Transfer of FcRI-expressing basophils into FcRI-deficient mice restored the development of the delayed-onset allergic inflammation. These findings indicate a novel mechanism of development of chronic allergic inflammation that is induced by basophils through the interaction of antigen, IgE, and FcRI.

Stem cell factor stimulates the chemotaxis, integrin upregulation, and survival of human basophils

BACKGROUND

Little is known about the mechanisms that regulate the selective recruitment of basophils to sites of allergic inflammation.

OBJECTIVE

Here we examine the role of stem cell factor (SCF) in the regulation of basophil function.

METHODS

Human basophils were isolated from peripheral blood, and their migration was investigated in chemotaxis assays. Apoptosis was detected by means of annexin V and propidium iodide staining. The expression of cell-surface molecules was measured by means of flow cytometry.

RESULTS

SCF amplified the chemotactic responsiveness of human peripheral blood basophils to the chemoattractants eotaxin, monocyte chemotactic protein 2 and macrophage inflammatory protein 1alpha, and C5a, without being chemotactic or chemokinetic by itself. SCF synergized with chemoattractants in causing basophil upregulation of the integrin CD11b, and this effect was inhibited by a c-kit antibody, the tyrosine kinase inhibitor imatinib mesylate (STI-571), and a phosphatidylinositol 3 kinase inhibitor but not by inhibitors of p38 mitogen-activated protein kinase or mitogen-activated protein kinase/extracellular signal-regulated kinase kinase. Basophils bound fluorescence-labeled SCF and expressed its receptor, c-kit, which was markedly upregulated in culture for 24 to 48 hours in the presence of IL-3. Moreover, SCF prolonged basophil survival in concert with IL-3 by delaying apoptosis. These effects of SCF were selective for basophils because chemotaxis and CD11b upregulation of eosinophils or neutrophils were unchanged.

CONCLUSION

SCF might be an important selective modulator of basophil function through a phosphatidylinositol 3 kinase-dependent pathway.

Organic cation transporter 3 modulates murine basophil functions by controlling intracellular histamine levels

In this study, we identify the bidirectional organic cation transporter 3 (OCT3/Slc22a3) as the molecule responsible for histamine uptake by murine basophils. We demonstrate that OCT3 participates in the control of basophil functions because exogenous histamine can inhibit its own synthesis--and that of interleukin (IL)-4, IL-6, and IL-13--through this means of transport. Furthermore, ligands of H3/H4 histamine receptors or OCT3 inhibit histamine uptake, and outward transport of newly synthesized histamine. By doing so, they increase the histamine content of basophils, which explains why they mimic the effect of exogenous histamine. These drugs were no longer effective in histamine-free histidine decarboxylase (HDC)-deficient mice, in contrast with histamine itself. Histamine was not taken up and lost its inhibitory effect in mice deficient for OCT3, which proved its specific involvement. Intracellular histamine levels were increased strongly in IL-3-induced OCT3-/- bone marrow basophils, and explained why they generated fewer cytokines than their wild-type counterpart. Their production was enhanced when histamine synthesis was blocked by the specific HDC inhibitor alpha-fluoro-methyl histidine, and underscored the determinant role of histamine in the inhibitory effect. We postulate that pharmacologic modulation of histamine transport might become instrumental in the control of basophil functions during allergic diseases.

Negative control of basophil expansion by IRF-2 critical for the regulation of Th1/Th2 balance

Although basophils are known to produce interleukin 4 (IL-4), the roles of these cells have been documented only in mice infected with parasites or in the effector phase of allergic inflammations. Here we show that naive mice lacking the transcription factor, interferon regulatory factor 2 (IRF-2), exhibited signal transducer and activator of transcription 6 (Stat6)–independent expansion of basophils in the periphery. IRF-2 appeared to act autonomously in the cells to negatively regulate the expansion of, but not cytokine production by, basophils. Spontaneous Th2 polarization of CD4+ T cells was observed in these mice and the genetic reduction of basophil numbers by mutating the Kit gene abolished such a polarization in vivo. We also found that both basophils and IL-4 derived from them were indeed essential for Th2 development under neutral conditions in vitro. Furthermore, neutralization of IL-3 abolished IL-4 production by basophils during Th1/Th2 differentiation cultures and subsequent Th2 development. These results indicated that basophils acted as a cellular converter to turn the neutral IL-3 into the Th2-inducing IL-4 during the initiation of Th1/Th2 differentiation. Thus, the negative regulatory role of IRF-2 on the basophil population size is critically important for preventing excess Th2 polarization and the Th1/Th2 balance in naive animals.

Seafood allergy: lessons from clinical symptoms, immunological mechanisms and molecular biology

Food allergy consists of a wide range of disorders that result from adverse immune responses to dietary antigens. Manifestations of allergic response includes acute, potentially fatal anaphylactic reactions and a variety of chronic diseases that mainly affect the gastrointestinal tract, skin, and respiratory tract. Tools for clinical diagnosis and management, which have not changed much in the past two decades, include the clinical history, tests for specific IgE antibody to suspected foods, elimination diets, oral food challenges, and provision of medications such as epinephrine for emergency treatment. On the other hand, recent immunological and molecular biological research have enhanced our understanding of the mechanisms of these disorders and revealed the identities of many food allergens. Here, we will discuss seafood allergies with respect to the clinical manifestations, diagnosis, immunological mechanisms, and molecular biology of seafood allergens. Furthermore, potential applications and future directions in the clinical management of seafood allergies are discussed.

Nerve growth factor influences IgE-mediated human basophil activation: functional properties and intracellular mechanisms compared with IL-3

NGF and IL-3 play a unique role in supporting human basophil differentiation and mediator secretion. Their importance in allergic disease is underlined further by studies showing elevated levels of these factors in asthmatics. Here, we compared the abilities of IL-3 and NGF to stimulate basophil histamine, IL-4 or IL-13 release, either directly or in conjunction with IgE-dependent stimulation and assessed the intracellular signals responsible. Our results show that the ability of IL-3 and NGF to enhance IgE-dependent histamine release are similar. Both factors also potentiated IgE-dependent IL-13 secretion to a greater degree than the release of histamine or IL-4. At high concentrations (100 ng/ml), IL-3 and NGF alone were capable of releasing cytokines but little histamine. These abilities of IL-3 and NGF to modulate basophil activation were sensitive to blockade by specific inhibitors of PI 3-kinase, p38 MAPK and PLC, but not PKC, suggesting that their effects are mediated considerably by pathways comparable to IgE-dependent signalling.

The basophil activation test by flow cytometry: recent developments in clinical studies, standardization and emerging perspectives

The diagnosis of immediate allergy is mainly based upon an evocative clinical history, positive skin tests (gold standard) and, if available, detection of specific IgE. In some complicated cases, functional in vitro tests are necessary. The general concept of those tests is to mimic in vitro the contact between allergens and circulating basophils. The first approach to basophil functional responses was the histamine release test but this has remained controversial due to insufficient sensitivity and specificity. During recent years an increasing number of studies have demonstrated that flow cytometry is a reliable tool for monitoring basophil activation upon allergen challenge by detecting surface expression of degranulation/activation markers (CD63 or CD203c). This article reviews the recent improvements to the basophil activation test made possible by flow cytometry, focusing on the use of anti-CRTH2/DP2 antibodies for basophil recognition. On the basis of a new triple staining protocol, the basophil activation test has become a standardized tool for in vitro diagnosis of immediate allergy. It is also suitable for pharmacological studies on non-purified human basophils. Multicenter studies are now required for its clinical assessment in large patient populations and to define the cut-off values for clinical decision-making.

Echinococcus multilocularis metacestode extract triggers human basophils to release interleukin-4

Infections with parasitic helminths are associated with a T helper 2 (Th2) immune response and IgE production. The underlying mechanism, however, is only partially understood. Recently we have isolated a protein from extracts of Schistosoma mansoni eggs that triggers human basophils from non-sensitized donors to release interleukin-4 (IL-4), the key cytokine of a Th2 response. We called this protein IPSE (for IL-4-inducing principle from Schistosoma mansoni eggs). Supposing that IPSE-like IL-4-inducing activities might be a general principle shared among different helminth species, we investigated extracts from the cestode E. multilocularis for its effect on human basophils. Our results showed that extracts from metacestodes of E. multilocularis cause basophil degranulation, as well as the secretion of histamine, IL-4 and IL-13, in a dose-dependent manner. IgE stripping and resensitization of basophils indicated that the mechanism of IL-4 induction requires the presence of IgE on the cells. Since analogous properties have been demonstrated earlier for IPSE, we think that S. mansoni and E. multilocularis may induce a Th2 response in their hosts via a related mechanism, namely, by the induction of IL-4 release from basophils.

Development of an in vitro system for the study of allergens and allergen-specific immunoglobulin E and immunoglobulin G: Fce receptor I supercross-linking is a possible new mechanism of immunoglobulin G-dependent enhancement of type I allergic reactions

BACKGROUND

IgE-dependent activation of mast cells (MCs) is a key pathomechanism of type I allergies. In contrast, allergen-specific IgG Abs are thought to attenuate immediate allergic reactions by blocking IgE binding and by cross-linking the inhibitory Fcgamma receptor IIB on MCs.

OBJECTIVES

To establish a defined in vitro system using human MCs to study the biological activity of allergens and to investigate the role of allergen-specific IgE and IgG.

METHODS

Purified human intestinal MCs sensitized with different forms of specific IgE Abs were triggered by monomeric and oligomeric forms of recombinant Bet v 1, the major birch pollen allergen, in the presence or absence of allergen-specific IgG Abs. Results MCs sensitized with an anti-Bet v 1 IgE mAb or sera obtained from birch pollen allergic patients released histamine and sulphidoleukotrienes after exposure to oligomeric Bet v 1. Monomeric Bet v 1 provoked mediator release only in MCs sensitized with patients sera but not in MCs sensitized with anti-Bet v 1 IgE mAb. Interestingly, MC activation could be induced by supercross-linking of monomeric Bet v 1 bound to monovalent IgE on MCs with a secondary allergen-specific IgG pAb. By using IgG F(ab')2 fragments we provide evidence that this effect is not a result of IgG binding to Fcgamma receptors.

CONCLUSION

This assay represents a new tool for the in vitro study of MC activation in response to natural and genetically modified allergens. Fcepsilon receptor I supercross-linking by allergen-specific IgG Abs provides a possible new mechanism of IgG-dependent enhancement of type I allergic reactions.

Identification of CD13, CD107a, and CD164 as novel basophil-activation markers and dissection of two response patterns in time kinetics of IgE-dependent upregulation

Using two-colour flow cytometry >200 antibodies submitted to the 8th International Workshop of Human Leukocyte Differentiation Antigens (HLDA8) have been analyzed for their reactivity with resting and activated CD203c+ basophils. Four antibodies either non-reactive or weakly reactive with resting basophils exhibited an increased reactivity with basophils activated by anti-IgE-mediated cross-linking of the high affinity IgE receptor (FceRI). These include antibodies against CD164 (WS-80160, clone N6B6 and WS-80162, clone 67D2), as well as two reagents with previously unknown specificities that were identified as CD13 (WS-80274, clone A8) and CD107a (WS-80280, clone E63-880). The activation patterns followed either the "CD203c-like" or "CD63-like" activation profile. The CD203c profile is characterized by a rapid and significant upregulation (of CD13, CD164, and CD203c), reaching maximum levels after 5-15 min of stimulation. The Phosphoinositide-3-kinase (PI3K)-specific inhibitor Wortmannin inhibited the upregulation of these markers whereas 12-O-tetradecanoyl-phorbol-13-acetate (TPA) induced a rapid and FceRI-independent upregulation within 1-2 min. In the CD63 profile, maximum upregulation (of CD63 and CD107a) was detected only after 20-40 min, and upregulation by TPA reached maximum levels after 60 min. In summary, our data identify CD13, CD107a, and CD164 as novel basophil-activation antigens. Based on time kinetics of upregulation, we hypothesize that molecules of the "CD203c group" and the "CD63 group" are linked to two different mechanisms of basophil activation.

Differential Role for Mitogen-Activated Protein Kinases in IgE-Dependent Signaling in Human Peripheral Blood Basophils: In Contrast to p38 MAPK, c-Jun N-Terminal Kinase Is Poorly Expressed and Does Not Appear to Control Mediator Release

BACKGROUND

Exposure of human basophils to allergens results in a rapid secretion of histamine, LTC(4), IL-4 and IL-13, which dominate both the symptomology of allergic diseases and support the underlying Th2/IgE predominance associated with these reactions. The IgE-dependent release of these mediators in basophils crucially involves PI 3-kinase and the subsequent activation of p38 MAPK and ERK1&2. Here, we investigated the role of the third major member of the mitogen activated kinase family, namely the c-Jun amino terminal kinase (JNK), which is rapidly activated following IgE receptor cross-linking in murine mast cells.

METHODS

Human basophils were highly purified by magnetic cell sorting. The activities of various intracellular signaling components, in basophils that had been stimulated under various conditions, were assessed by Western blotting. Mediator secretions were also determined using either spectrofluorometric analysis (histamine) or ELISA (LTC(4), IL-4 and IL-13).

RESULTS

Our results show that while JNK is moderately expressed in human basophils, it is not consistently phosphorylated upon anti-IgE stimulation. Phosphorylation of the transcription factor c-Jun, a downstream target of JNK, was also undetected in contrast to p38 MAPK and ERK1&2, which were clearly activated following anti-IgE stimulation of the cells. Additionally, inhibitors of the JNK pathway failed to prevent basophil mediator release and had no effect on the phosphorylation of p38 MAPK or ERK1&2 at concentrations which were specific for JNK blockade.

CONCLUSIONS

These data suggest major differences in utilizing various members of the mitogen-activated kinase family in the signal transduction cascade of IgE-receptor-bearing cells.

JTP-27536 [(+)-1,3-dihydroxy-2-hydroxymethylpropyl-2-ammonium 2-[(R)-3-cyclo-hexyl-1-phenylpropyl]-1,3-dioxo-2,3-dihydro-1H-isoindole-5-carboxylate monohydrate], a novel inhibitor of immunoglobulins and interleukin-5 with anti-inflammatory properties in mouse allergic dermatitis model

We report a novel synthetic compound JTP-27536 [(+)-1,3-dihydroxy-2-hydroxymethylpropyl-2-ammonium 2-[(R)-3-cyclohexyl-1-phenylpropyl]-1,3-dioxo-2,3-dihydro-1H-isoindole-5-carboxylate monohydrate] as an inhibitor of immunoglobulins (Igs) and interleukin (IL)-5 production in vitro and in vivo. JTP-27536 inhibited IgE production in mouse and human B cells with IC50 values of 2.5 and 2.1 microM, respectively, and the inhibition was stronger than that on IgG1 and IgM production (IC50 > 10 microM). JTP-27536 also inhibited IL-5 production in mouse splenocytes and human peripheral blood mononuclear cells with IC50 values of 3.3 and 1.3 microM, respectively, without affecting mouse interferon (IFN)-gamma, IL-2, IL-4, IL-10, or human IL-4 production. In contrast, prednisolone not only inhibited mouse IgE production but also mouse IFN-gamma, IL-2, IL-4, and IL-10 and human IL-4 and IL-5 production in vitro. The effect of suplatast tosilate, a Th2 cytokine inhibitor, on antibody and cytokine production was less potent than that of JTP-27536. In vivo animal experiments using dinitrophenylated ascaris-sensitized mice and 2,4,6-trinitro-1-chrolobenzene-induced chronic dermatitis mice showed that JTP-27536 was more potent than suplatast tosilate and comparable with prednisolone in inhibiting ear swelling, antigen-specific IgE and IL-5 production, and cell infiltrations into the inflamed tissue. These results indicate that JTP-27536 is an inhibitor of Igs, in particular IgE, and of IL-5, which has antiallergic properties in mouse dermatitis model, and suggest that an inhibitor of Igs and IL-5 like JTP-27536 may be useful as a drug for the treatment of allergic diseases.

Gastrointestinal food allergy: new insights into pathophysiology and clinical perspectives

Adverse reactions to food that result in gastrointestinal symptoms are common in the general population; while only a minority of such individuals will have symptoms due to immunologic reactions to foods, gastrointestinal food allergies do exist in both children and adults. These immune reactions are mediated by immunoglobulin E-dependent and -independent mechanisms involving mast cells, eosinophils, and other immune cells, but the complexity of the underlying mechanisms of pathogenesis have yet to be fully defined. Knowledge of the spectrum of adverse reactions to foods that affect the digestive system, including gastrointestinal food allergy, is essential to correctly diagnose and manage the subset of patients with immunologically mediated adverse reactions to foods. Potentially fatal reactions to food necessitate careful instruction and monitoring on the part of health care workers involved in the care of individuals at risk of anaphylaxis. New methods of diagnosis and novel strategies for treatment, including immunologic modulation and the development of hypoallergenic foods, are exciting developments in the field of food allergy.

Histamine-cytokine connection in immunity and hematopoiesis

A number of recent studies have led to a reappraisal of the functional capacities of histamine in immunity and hematopoiesis. This change of perspective was provided by the following findings: (1) the evidence for multiple cellular sources of histamine, differing from mature basophils and mast cells by their ability to newly synthesize and liberate the mediator without prior storage, (2) the discovery of a novel histamine receptor (H4R), preferentially expressed on hematopoietic and immunocompetent cells, (3) the potential intracellular activity of histamine through cytochrome P450 and (4) the demonstration of a histamine-cytokine cross-talk. Indeed, cytokines not only modulate the degranulation process of histamine but also control its neosynthesis by the histamine-forming enzyme, histidine decarboxylase (HDC), at transcriptional and post-transcriptional levels. In turn, histamine intervenes in the intricate cytokine network, regulating cytokine production by immune cells through distinct receptors signaling distinct biological effects. This type of regulation is particularly relevant in the context of TH1/TH2 differentiation, autoimmunity and tumor immunotherapy.

Identification of antigen-capturing cells as basophils

Binding of intact Ag is a hallmark of Ag-specific B cells. Apart from B cells, a small number of non-B cells can bind Ag with comparable efficacy as B cells and are found in the peripheral blood, spleen, and bone marrow of mice. This population has been observed for a long time and recently named "Ag-capturing cells." Their identity remained enigmatic. In this study, we show that these cells are basophilic granulocytes. Their ability to capture Ags is dependent on surface IgE receptors and on Ag-specific plasma IgE molecules appearing after immunization. Several surface markers including surface bound IgE, IL-3R, CD45, CD16/32, and the chemokine receptor CCR2 were used to clearly identify these cells. Cross-linkage of surface Igs results in the release of large amounts of IL-4 and IL-6. The data identify basophils as Ag-capturing cells and support the concept of basophils as important regulators of humoral immune responses.

Role of human mast cells and basophils in bronchial asthma

Mast cells and basophils are the only cells expressing the tetrameric (alphabetagamma2) structure of the high affinity receptor for IgE (FcepsilonRI) and synthesizing histamine in humans. Human FcepsilonRI+ cells are conventionally considered primary effector cells of bronchial asthma. There is now compelling evidence that these cells differ immunologically, biochemically, and pharmacologically, which suggests that they might play distinct roles in the appearance and fluctuation of the asthma phenotype. Recent data have revealed the complexity of the involvement of human mast cells and basophils in asthma and have shed light on the control of recruitment and activation of these cells in different lung compartments. Preliminary evidence suggests that these cells might not always be detrimental in asthma but, under some circumstances, they might exert a protective effect by modulating certain aspects of innate and acquired immunity and allergic inflammation.

Involvement of Rab27 in antigen-induced histamine release from rat basophilic leukemia 2H3 cells

The Rab family small G proteins regulate discrete steps in vesicular transport pathways. Recent studies indicate that one member of the Rab family, Rab27A, regulates the transport of lysosome-related organelles, such as melanosome distribution in melanocytes, lytic granule release in cytotoxic T cells, and dense granule release in platelets. Here, we have examined the involvement of Rab27A in the exocytic transport of another lysosome-related organelle, the basophilic secretory granule, in basophils. We have found that Rab27A locates on basophilic secretory granules containing histamine in rat basophilic leukemia (RBL) 2H3 cells. In addition, exogenous expression of dominant active Rab27A reduces antigen-induced histamine release from the cells. We have moreover identified Munc13-4 as a Rab27A target using a CytoTrap system and found that exogenous expression of Munc13-4 affects antigen-induced histamine release from RBL-2H3 cells. These results demonstrate that Rab27A plays a crucial role in antigen-induced histamine release from RBL-2H3 cells.

Identification of Selective Basophil Chemoattractants in Human Nasal Polyps as Insulin-Like Growth Factor-1 and Insulin-Like Growth Factor-2

In a search for novel leukocyte chemoattractants at sites of allergic inflammation, we found basophil-selective chemoattractant activity in extracts of human nasal polyps. The extracts were fractionated by reverse phase HPLC, and the resulting fractions were tested for leukocyte-stimulating activity using sensitive shape change assays. The basophil-selective activity detected was not depleted by a poxvirus CC-chemokine-binding protein affinity column. This activity was further purified by HPLC, and proteins in the bioactive fractions were analyzed by tandem electrospray mass spectrometry. Insulin-like growth factor-2 (IGF-2) was identified in these HPLC fractions, and the basophil-stimulating activity was inhibited by an anti-IGF-2-neutralizing Ab. Recombinant IGF-2 induced a substantial shape change response in basophils, but not eosinophils, neutrophils, or monocytes. IGF-2 stimulated chemokinesis of basophils, but not eosinophils or neutrophils, and synergized with eotaxin-1/CCL11 in basophil chemotaxis. IGF-2 also caused up-regulation of basophil CD11b expression and inhibited apoptosis, but did not stimulate degranulation or Ca(2+) flux. Recombinant IGF-1 exhibited similar basophil-selective effects as IGF-2, and both growth factors were detected in nasal polyp extracts by ELISA. This is the first demonstration of chemokinetic factors that increase the motility of basophils, but do not act on other granulocytes or monocytes. IGF-1 and IGF-2 could play a role in the selective recruitment of basophils in vivo.

Assays for measuring in vitro basophil activation induced by recombinant allergens

The diagnosis of type I allergy is essentially based on clinical data, skin tests, and measurements of allergen-specific IgE. However, the determination of specific IgE per se does not permit a definitive conclusion concerning the response of effector cells to the respective allergen(s) and consecutive clinical symptoms in all patients. In an attempt to overcome this problem, a number of basophil-activation assays have been developed during the last few years. Today, allergen-induced activation of blood basophils can be employed as a specific and reliable measure of IgE-dependent responses in sensitized individuals. Using recombinant allergens and basophil-specific markers, these novel assays appear to serve as simple and useful tests in component-resolved diagnosis of type I allergies. In the current article, the biochemical, functional, and technical background of these basophil tests is discussed.

Effects of Prostaglandin D2and 5-Lipoxygenase Products on the Expression of CD203c and CD11b by Basophils

Basophils are important in allergic diseases such as asthma because they produce a variety of inflammatory mediators. Activation of these cells with IgE and N-formyl-methionyl-leucyl-phenylalanine results in a variety of responses, including increased surface expression of CD203c and CD11b and release of histamine. Although considerable information is available on the effects of eicosanoids on neutrophils, eosinophils, and monocytes, less is known about their effects on basophils. In the present study, we examined the effects of various eicosanoids on the above basophil responses. Of the naturally occurring eicosanoids tested, prostaglandin D(2) (PGD(2); EC(50), 10 nM) was by far the most potent activator of CD203c expression, with other prostanoids having little effect. This response was mediated by the DP(2) receptor/chemoattractant receptor-homologous molecule expressed on Th2 cells because it was shared by the selective agonist 15R-methyl-PGD(2) (EC(50), 3 nM). The 5-lipoxygenase products leuko-triene B(4) and 5-oxo-6,8,11,14-eicosatetraenoic acid also stimulated CD203c expression but to a lesser extent than PGD(2), whereas leukotriene D(4) was inactive. Neither PGD(2) nor 5-oxo-6,8,11,14-eicosatetraenoic acid stimulated histamine release or CD63 expression on basophils. Both PGE(2) and the DP(1) receptor agonist BW245C [(4S)-(3-[(3R,S)-3-cyclohexyl-3-hydroxypropyl]-2,5-dioxo)-4-imidazolidineheptanoic acid] strongly inhibited DP(2) receptor-mediated CD203c expression. The DP(1) receptor antagonist BWA868C [3-[(2-cyclohexyl-2-hydroxyethyl)amino]-2,5-dioxo-1-(phenylmethyl)-4-imidazolidine-heptanoic acid] enhanced PGD(2)-induced CD203c expression, suggesting that interaction of PGD(2) with DP(1) receptors can limit activation of basophils by this prostaglandin. In conclusion, PGD(2) is the most potent inducer of basophil CD203c expression among eicosanoids and may be a key mediator in asthma and other allergic diseases. The balance between DP(1) and DP(2) receptors may be important in determining the magnitude of basophil responses to this prostaglandin.

Bioinformatics for the 'bench biologist': how to find regulatory regions in genomic DNA

The combination of bioinformatic and biological approaches constitutes a powerful method for identifying gene regulatory elements. High-quality genome sequences are available in public databases for several vertebrate species. Comparative cross-species sequence analysis of these genomes shows considerable conservation of noncoding sequences in DNA. Biological analyses show that an unexpectedly high number of the conserved sequences correspond to functional cis-regulatory regions that influence gene transcription. Because research biologists are often unfamiliar with the bioinformatic resources at their disposal, this commentary discusses how to integrate biological and bioinformatic methods in the discovery of gene regulatory regions and includes a tutorial on widely available comparative genomics programs.

The mast cell: an antenna of the microenvironment that directs the immune response

Mast cells (MCs) have long been considered as critical effector cells during immunoglobulin (Ig)E-mediated allergic disease and immune response to parasites. Recent studies, however, suggest that this understanding of MC function is incomplete and does not consider the complex roles that MCs play in adaptive and innate immunity. The added function gives an innovative vision of regulation of immune responses and the development of autoimmune diseases. It had been assumed that the aggregation of Fc epsilon receptor I with IgE and specific antigen is the main stimulus able to induce the MC activation, degranulation, release, and generation of mediators of the allergic reaction. However, MCs exhibit an array of molecules involved in cell-cell and cell-extracellular matrix adhesion, mediating delivery of costimulatory signals that empower those cells with an ability to react to multiple nonspecific and specific stimuli. Their tissue distribution and their capability to release many cytokines after stimulation indicate MCs as potential regulatory linkers between innate and acquired immunity. In this review, we will summarize some findings on the roles of MCs in innate and acquired immunity, on the molecular mechanism and signaling pathways, and on selective signals that induce discrete MC response and its ability to polarize adaptive-immune response.