Cell biology of the basophil

Integrated microRNA and mRNA expression profile analysis of tumor-associated macrophages after exposure to single-dose irradiation

BACKGROUND

Radiotherapy (RT) is a common approach that accounts for nearly 50% of cancer patient treatment and has the potential for long-term tumor control. Recently, we published a research article on gene expression profiling of tumor-associated macrophages (TAM) that were exposed to ionizing radiation (IR). Single-dose irradiation of tumors could initiate differentially expressed genes in TAM as a time series from irradiated tumors that are associated with the immune response. It is also well known that human cancers are associated with microRNA (miRNA) alterations that are involved in cancer progression. However, the role of miRNA on TAM after exposure to irradiation remains unclear.

RESULTS

In this study, miRNA expression profiles from microarrays were used to identify the key miRNAs and correlating pathways involved in the role of TAMs in tumor progression and recurrence after RT. Using a mouse tumor model, we identified miRNA pattern changes over time in response to irradiation. Based on our results, we hypothesize that miRNA expression in the irradiated tumor may be used as a distinguishing marker to indicate the best time for therapeutic intervention to prevent tumor recurrence after RT.

CONCLUSIONS

We established a murine model irradiated with a single dose of 25 Gy that could initiate temporal changes in the expression of miRNAs associated with cell proliferation and the immune response, as evidenced by macrophages directly extracted from irradiated tumors after two weeks of IR. Statistical analyses were conducted by comparing the miRNA expression in macrophages from non-irradiated versus irradiated tumors. Thus, our study could lead to a better understanding of the function of miRNA expressions, which changed temporally in an irradiated tumor microenvironment.

Identification of a New Exo-Endocytic Mechanism Triggered by Corticotropin-Releasing Hormone in Mast Cells

The key role of mast cells (MC), either in development of inflammatory pathologies or in response to environmental stress, has been widely reported in recent years. Previous studies have described the effects of corticotropin-releasing hormone (CRH), which is released from inflamed tissues by cellular stress signals, on MC degranulation, a process possibly driven by selective secretion of mediators (piecemeal degranulation). In this study, we introduce a novel granular exo-endocytic pathway induced by CRH on peritoneal MC. We found that CRH triggers substantial exocytosis, which is even stronger than that induced by Ag stimulation and is characterized by large quantal size release events. Membrane fluorescence increases during stimulation in the presence of FM1-43 dye, corroborating the strength of this exocytosis, given that discrete upward fluorescence steps are often observed and suggesting that secretory granules are preferentially released by compound exocytosis. Additionally, the presence of a depot of large tubular organelles in the cytoplasm suggests that the exocytotic process is tightly coupled to a fast compound endocytosis. This CRH-stimulated mechanism is mediated through activation of adenylate cyclase and an increase of cAMP and intracellular Ca(2+), as evidenced by the fact that the effect of CRH is mimicked by forskolin and 8-bromo-cAMP. Thus, these outcomes constitute new evidence for the critical role of MC in pathophysiological conditions within a cellular stress environment and an alternative membrane trafficking route mediated by CRH.

Role of interleukins in the regulation of basophil development and secretion

PURPOSE OF REVIEW

It is well appreciated that differentiation, growth, and function of basophils are regulated by a network of cytokines, and that these cells express a unique composition of surface receptors including interleukin-binding sites. In the current article, most recent discoveries around cytokine regulation of basophils are discussed and compared with previous data.

RECENT FINDINGS

Confirming previous studies, the most potent growth factor for basophils remains interleukin (IL)-3, followed by granulocyte-macrophage colony-stimulating factor and IL-5. These cytokines also act on mature basophils through specific receptors, thereby mediating adhesion, migration, and releasability. Other molecules regulating basophil function are chemokines such as IL-8 or eotaxin and IL-33. Especially IL-33 has been described as a novel basophil regulator. All cytokines act on basophils via specific receptors and signal transduction pathways. The present article provides a summary of our knowledge on cytokine regulation of basophils and receptor expression, with emphasis on most recent developments in the field.

SUMMARY

Basophil regulation by cytokines in health and disease may be a more complex process than has been considered previously. Some of the affected cytokine cascades, receptors, and signal transduction molecules may serve as targets of therapy in 'basophil activation disorders' in the future.

Flow-assisted allergy diagnosis: current applications and future perspectives

Physicians predominantly rely upon quantification of serum-specific immunoglobulin E (IgE) and/or skin test to confirm clinically suspected IgE-mediated allergy. However, for various reasons, identification of the offending allergen(s) and potentially cross-reactive structures is not always straightforward. Flow-assisted allergy diagnosis relies upon quantification of alterations in the expression of particular basophilic activation markers. Actually, upon challenge with a specific allergen, basophils not only secrete quantifiable bioactive mediators but also upregulate the expression of different markers which can be detected efficiently by flow cytometry using specific monoclonal antibodies. Currently, the technique has been applied in the investigation of IgE-mediated allergy caused by classical inhalant allergens, food, Hevea latex, hymenoptera venoms and drugs. It is also appreciated; the technique proves valuable in the diagnosis of non-IgE-mediated (anaphylactoid) reactions such drug hypersensitivity and the detection of autoantibodies in certain forms of chronic urticaria. This review will not address immunologic features, characteristics and general pitfalls of flow-assisted analysis of in vitro-activated basophils as summarized elsewhere. After a recapitulation of the principles and some specific technical issues of flow-assisted analysis of in vitro-activated basophils, we principally focus on the current clinical and research applications of the basophil activation tests. Personal experience of both research groups is provided, where appropriate. Finally, a viewpoint on how the field might evolve in the following years is provided.

Enumeration and immunohistochemical characterisation of bone marrow basophils in myeloproliferative disorders using the basophil specific monoclonal antibody 2D7

BACKGROUND

Basophils are highly specialised granulocytes that express a unique profile of antigens and increase in myeloproliferative disorders (MPD). In chronic myeloid leukaemia (CML), basophilia is a diagnostic and prognostic determinant. So far, however, no reliable approach for routine detection and enumeration of bone marrow basophils has become available.

OBJECTIVE

To detect and enumerate basophils in bone marrow sections in patients with CML and other MPD.

METHODS

The anti-basophil antibody 2D7 was applied to paraffin embedded bone marrow sections from normal/reactive subjects (n = 31), patients with CML (chronic phase, n = 37; accelerated phase, n = 9), and other MPD (chronic idiopathic myelofibrosis (CIMF), n = 20; polycythaemia vera (PV), n = 20; essential thrombocythaemia (ET), n = 20; indolent systemic mastocytosis (ISM), n = 7).

RESULTS

As assessed by serial section staining, 2D7(+) cells were found to co-express myeloperoxidase, histidine decarboxylase, CD9, and CD43, but did not express B cell or T cell restricted antigens. 2D7(+) bone marrow cells were found to increase in CML compared with normal/reactive bone marrow and other MPD (median numbers of 2D7(+) cells/mm(2): CML, 33; normal/reactive bone marrow, 6; CIMF, 10; PV, 6; ET, 5; ISM, 3; p<0.05). The highest basophil counts were recorded in accelerated phase CML (115/mm(2)).

CONCLUSIONS

A novel immunohistochemical procedure has been established for basophil detection in normal bone marrow and MPD. This approach should help in the quantification of bone marrow basophils at diagnosis and during anti-leukaemic treatment.

Ultrastructural studies of human basophils and mast cells

Ultrastructural studies of human mast cells (HMCs) and basophils (HBs) are reviewed. Sources of HMCs include biopsies of tissue sites and in situ study of excised diseased organs; isolated, partially purified samples from excised organs; and growth-factor-stimulated mast cells that develop de novo in cultures of cord blood cells. Sources of HBs for study include partially purified peripheral blood basophils, basophils in tissue biopsies, and specific growth factor-stimulated basophils arising de novo from cord blood cells. The ultrastructural studies reviewed deal with identity, secretion, vesicles, recovery, and synthesis issues related to the biology of these similar cells.

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.

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.

Piecemeal degranulation as a general secretory mechanism?

In this article we review the ultrastructural findings, functional aspects, and biological significance of piecemeal degranulation (PMD), a unique secretory pathway that has been described in basophils, mast cells, and eosinophils. Recent ultrastructural data suggestive of PMD in enteroendocrine cells of the gastrointestinal tract and chromaffin cells of the adrenal medulla are also presented and discussed. Further research on PMD in secretory cells of the endocrine and exocrine glands, as well as in neurons, is recommended, since the current data indicate that PMD has a broader spectrum of expression than was hitherto reported. The identification of the PMD phenotype in different cell types (e.g., basophils, mast cells, eosinophils, enteroendocrine cells, and adrenal chromaffin cells) suggests that PMD is a unique degranulation model for paracrine and endocrine secretion. Further investigation will clarify whether PMD can be considered as a general mechanism for the slow release of bioactive stored materials by granulated secretory cells.

Ultrastructural morphology of adrenal chromaffin cells indicative of a process of piecemeal degranulation

Chromaffin cells of the mouse adrenal medulla were found by transmission electron microscopy (TEM) to exhibit ultrastructural changes suggestive of piecemeal degranulation (PMD), a unique model of cell secretion characterized by the slow release of granule materials without granules opening to the cell exterior. The expression of PMD was recognized in both adrenaline- and noradrenaline-containing cells. Ultrastructural changes included specific granule and cytoplasmic morphologies. In adrenaline-releasing cells the granule content was loosely packed or condensed, and surrounded by a clear halo. In noradrenaline-storing cells, the granule material appeared asymmetrically arranged and exhibited characteristic "semilunar" electron-dense domains within the granule chambers. Notably, altered granules did not fuse with each other or with the plasma membrane, and were intermingled with normal, resting granules. Large, empty cytoplasmic containers or vacuoles filled with partially dissolved matrices were frequently observed. In addition, both adrenaline- and noradrenaline-storing cells presented a rich supply of membrane-bound, smooth vesicles (50-200 nm diameter) that were either free in the cytoplasm or attached to granules. The finding of ultrastructural features characteristic of PMD in adrenal chromaffin cells suggests that such a secretory model may be an alternative secretory pathway to regulated exocytosis. Moreover, these results support the hypothesis that PMD may be a general degranulation pattern in cells involved in paracrine-endocrine secretion.

Cerivastatin and atorvastatin inhibit IL-3-dependent differentiation and IgE-mediated histamine release in human basophils and downmodulate expression of the basophil-activation antigen CD203c/E-NPP3

Recent data suggest that the statins, apart from their lipid-lowering activity, exhibit profound anti-inflammatory effects. Basophils are major proinflammatory effector cells in diverse pathologic reactions. We have examined the in vitro effects of five different statins on primary human basophils, their progenitors, and the basophil cell line KU-812. Preincubation of blood basophils with cerivastatin or atorvastatin (0.1-100 microM) for 24 h reduced their capacity to release histamine on immunoglobulin E (IgE)-dependent stimulation in a dose-dependent manner. These statins also inhibited IgE-dependent up-regulation of the basophil-activation antigen CD203c. Moreover, both statins suppressed interleukin-3-induced differentiation of basophils from their progenitors as well as (3)H-thymidine uptake in KU-812 cells. All inhibitory effects of cerivastatin and atorvastatin were reversed by mevalonic acid (200 microM). The other statins tested (lovastatin, simvastatin, pravastatin) did not show significant inhibitory effects on basophils. Together, these data identify cerivastatin and atorvastatin as novel inhibitors of growth and activation of human basophils.

Helper T cells regulate type-2 innate immunity in vivo

Type-2 immunity requires orchestration of innate and adaptive immune responses to protect mucosal sites from pathogens. Dysregulated type-2 responses result in allergy or asthma. T helper 2 (T(H)2) cells elaborate cytokines, such as interleukin (IL)-4, IL-5, IL-9 and IL-13, which work with toxic mediators of innate immune cells to establish environments that are inhospitable to helminth or arthropod invaders. The importance of T(H)2 cells in coordinating innate immune cells at sites of inflammation is not known. Here we show that polarized type-2 immune responses are initiated independently of adaptive immunity. In the absence of B and T cells, IL-4-expressing eosinophils were recruited to tissues of mice infected with the helminth Nippostrongylus brasiliensis, but eosinophils failed to degranulate. Reconstitution with CD4 T cells promoted accumulation of degranulated IL-4-expressing cells, but only if T cells were stimulated with cognate antigen. Degranulation correlated with tissue destruction, which was attenuated if eosinophils were depleted. Helper T cells confer antigen specificity on eosinophil cytotoxicity, but not cytokine responses, so defining a novel mechanism that focuses tissue injury at sites of immune challenge.

Granule changes of human and murine endocrine cells in the gastrointestinal epithelia are characteristic of piecemeal degranulation

Piecemeal degranulation is a unique pattern of cell secretion that consists of a slow release of granule contents from cytoplasmic secretory granules, which leaves empty chambers that do not fuse with each other or with the plasma membrane. To our knowledge, no cell types other than mast cells, basophils, and eosinophils have been reported in the literature to show morphological features of piecemeal degranulation. In the present study we provide evidence for ultrastructural morphologies characteristic of piecemeal degranulation in entero-endocrine cells of the human and murine gastrointestinal epithelia. Human biopsy samples were taken from the mucosa of the distal duodenum, proximal jejunum, and colon in 10 patients undergoing endoscopic examination for malabsorption, diarrhea, and/or abdominal pain. Murine gastrointestinal samples were obtained from 10 adult C57 mice. All specimens were prepared for transmission electron microscopy (TEM) according to standard protocols. Results showed that different types of gastrointestinal entero-endocrine cells, in both humans and mice, were recognizable with ultrastructural features diagnostic for piecemeal degranulation, including specific granule and cytoplasmic changes. In the granules, the content was found to be loosely packed or diminished. Notably, altered granules did not fuse with each other or with the plasma membrane, and were characteristically intermingled with normal, resting granules. At times, the release events transformed the granules into enlarged, empty containers. Numerous entero-endocrine cells presented a rich supply of membrane-bound vesicles (50-200 nm in diameter) that were free in the cytoplasm or attached to granules. This finding of piecemeal degranulation in gastrointestinal entero-endocrine cells suggests that such a secretory model might be a general degranulation pattern in cells involved in paracrine-endocrine secretion.

Pathogenesis of murine experimental allergic rhinitis: a study of local and systemic consequences of IL-5 deficiency

Recent studies have demonstrated an important role for IL-5-dependent bone marrow eosinophil progenitors in allergic inflammation. However, studies using anti-IL-5 mAbs in human asthmatics have failed to suppress lower airway hyperresponsiveness despite suppression of eosinophilia; therefore, it is critical to examine the role of IL-5 and bone marrow responses in the pathogenesis of allergic airway disease. To do this, we studied the effects of IL-5 deficiency (IL-5(-/-)) on bone marrow function as well as clinical and local events, using an established experimental murine model of allergic rhinitis. Age-matched IL-5(+/+) and IL-5(-/-) BALB/c mice were sensitized to OVA followed by 2 wk of daily OVA intranasal challenge. IL-5(-/-) OVA-sensitized mice had significantly higher nasal mucosal CD4(+) cells and basophilic cell counts as well as nasal symptoms and histamine hyperresponsiveness than the nonsensitized group; however, there was no eosinophilia in either nasal mucosa or bone marrow; significantly lower numbers of eosinophil/basophil CFU and maturing CFU eosinophils in the presence of recombinant mouse IL-5 in vitro; and significantly lower expression of IL-5Ralpha on bone marrow CD34(+)CD45(+) progenitor cells in IL-5(-/-) mice. These findings suggest that IL-5 is required for normal bone marrow eosinophilopoiesis, in response to specific Ag sensitization, during the development of experimental allergic rhinitis. However, the results also suggest that suppression of the IL-5-eosinophil pathway in this model of allergic rhinitis may not completely suppress clinical symptoms or nasal histamine hyperresponsiveness, because of the existence of other cytokine-progenitor pathways that may induce and maintain the presence of other inflammatory cell populations.

Detection of tryptase in cytoplasmic granules of basophils in patients with chronic myeloid leukemia and other myeloid neoplasms

Tryptases are serine proteases primarily expressed in mast cells. Normal blood basophils express only trace amounts of the enzyme. However, recent immunohistochemical studies have raised the possibility that neoplastic basophils express significant amounts of tryptase. In this study, tryptase expression was analyzed in normal and neoplastic basophils by immunoelectron microscopy using antitryptase monoclonal antibody G3. Basophils were obtained from patients with chronic myeloid leukemia (CML), idiopathic myelofibrosis (IMF), and myelodysplastic syndrome (MDS), and from healthy donors. Tryptase-immunoreactive material was detected in cytoplasmic granules of basophils in CML, IMF, and MDS. By contrast, normal basophils did not contain significant amounts of tryptase by immunoelectron microscopy. As assessed by reverse transcription-polymerase chain reaction, neoplastic basophils contained messenger RNA (mRNA) for alpha-tryptase, but no beta-tryptase mRNA. In summary, these data provide evidence that neoplastic basophils in CML, IMF, and MDS can express detectable amounts of tryptase. Therefore, tryptase should not be regarded as specific for mast cells when neoplastic myeloid cells are analyzed.

Ultrastructural immunogold cytochemistry with autoimmune human sera and an antibody to uridine implicate human mast cell granules in RNA biology

Human mast cells are professional secretory cells that store synthetic products in large granules filling their cytoplasm. Unlike many secretory cells, the principal synthetic organelle, ribosome-rich endoplasmic reticulum, is a minor component of their cytoplasm. Sightings of nonmembrane-bound ribosomes in and near their secretory granules stimulated detailed ultrastructural studies of various RNA species to implicate secretory-storage granules in RNA biology. In the work reported here, postembedding immunogold ultrastructural cytochemistry indicates that human mast cells contain uridine, an integral ingredient of RNA, and ribonucleoproteins, known to associate with small nuclear RNAs important for splicing RNA precursors, several ribonucleoproteins with possible functions in other aspects of RNA biology and ribonucleoproteins known to associate with ribosomes. These findings should catalyse future work toward establishing the full functional repertoire of secretory-storage granules.

Mass, charge, and subcellular localization of a unique secretory product identified by the basophil-specific antibody BB1

BACKGROUND

BB1 is a basophil-specific mAb (Lab Invest 1999;79:27-38). The identity of the corresponding antigen has not been determined, but it gives a granular appearance on staining and is secreted on activation of basophils.

OBJECTIVE

We sought to further characterize the basophilspecific antigen identified by BB1.

METHODS

Intracellular localization was determined by flow cytometry and by immunogold labeling and electron microscopy. Physical chemical properties were investigated by gel filtration chromatography and preparative isoelectric focusing.

RESULTS

In flow cytometry, permeabilization of cells increased immunofluorescence 100-fold, confirming the predominantly intracellular localization of the antigen. It was further localized to the secretory granules by immunoelectron microscopy. Double labeling with a CD63-specific antibody demonstrated selective binding of BB1 to the granule matrix. Gel filtration chromatography indicated that the antigen is secreted as a complex of approximately 5 x 10(6) d, which was well resolved from the 210-kd supramolecular complex containing tryptase. The antigen was degraded by pronase. Isoelectric focusing indicated a highly basic protein with an isoelectric point of 9.6.

CONCLUSION

With its granule localization, release on cell activation, and unique properties, the antigen identified by BB1 could be a novel mediator of allergic disease. We propose the name basogranulin for this novel basophil-specific protein.

Ultrastructural localization of vesicle-associated membrane protein(s) to specialized membrane structures in human pericytes, vascular smooth muscle cells, endothelial cells, neutrophils, and eosinophils

Vesicle-associated membrane proteins (VAMPs) are important to the trafficking of vesicles between membrane-bound intracytoplasmic organelles, in the facilitation of neurosecretion, and in constitutive and regulated secretion in non-neuronal cells. We used a pre-embedding ultrastructural immunonanogold method to localize VAMPs to subcellular sites in human cells of five lineages known to have cytoplasmic vesicles that may function in vesicular transport. We found VAMPs localized to caveolae in pericytes, vascular smooth muscle cells, and endothelial cells of venules, to the vesiculo-vacuolar organelle, recently defined in venular endothelial cells, to the vesicle-rich intergranular cytoplasm and secretory granule membranes of neutrophils, and to perigranular cytoplasmic secretory vesicles and secretory granule membranes in eosinophils. These specific localizations in five human vascular and granulocyte lineages support the notion that VAMPs have vesicle-associated functions in these cells.

Ribonuclease-gold labels chondroitin sulphate in guinea pig basophil granules

Basophilic leucocytes are metachromatic granule-containing secretory granulocytes that contain a mixture of granular proteoglycans devoid of heparin. In guinea pigs, isolated basophilic leucocyte granules primarily contain chondroitin sulphate. We have recently demonstrated that an enzyme-affinity-gold technique to image RNA, using the reagent RNase gold, also binds specifically to heparin in human mast cell granules. Such binding is based on the known property of heparin as a competitive inhibitor of RNase. Using similar methods, we show here that RNase-gold binds to the chondroitin sulphate in the secretory granules of guinea pig basophils, thus broadening the applicability of this post-embedding affinity-gold method to studies that require imaging of chondroitin sulphate in routinely prepared electron microscopical samples.