Studies of cell adhesion and flow cytometric analyses of degranulation, surface phenotype, and viability using human eosinophils, basophils, and mast cells

Targeted Interleukin-9 delivery in pulmonary hypertension: Comparison of immunocytokine formats and effector cell study

AIMS

Pulmonary hypertension (PH) is accompanied by pulmonary vascular remodelling. By targeted delivery of Interleukin-9 (IL9) via the immunocytokine F8IL9, beneficial effects could be demonstrated in a mouse model of PH. This study aimed to compare two immunocytokine formats (single-chain Fv and full IgG) and to identify potential target cells of IL9.

METHODS

The Monocrotaline mouse model of PH (PH, n = 12) was chosen to evaluate the treatment effects of F8IL9F8 (n = 12) and F8IgGIL9 (n = 6) compared with sham-induced animals (control, n = 10), the dual endothelin receptor antagonist Macitentan (MAC, n = 12) or IL9-based immunocytokines with irrelevant antigen specificity (KSFIL9KSF, n = 12; KSFIgGIL9 n = 6). Besides comparative validation of treatment effects, the study was focused on the detection and quantification of mast cells (MCs) and regulatory T cells (Tregs).

RESULTS

There was a significantly elevated systolic right ventricular pressure (104 ± 36 vs. 45 ± 17 mmHg) and an impairment of right ventricular echocardiographic parameters (RVbasal: 2.52 ± 0.25 vs. 1.94 ± 0.13 mm) in untreated PH compared with controls (p < 0.05). Only the groups treated with F8IL9, irrespective of the format, showed consistent beneficial effects (p < 0.05). Moreover, F8IL9F8 but not F8IgGIL9 treatment significantly reduced lung tissue damage compared with untreated PH mice (p < 0.05). There was a significant increase in Tregs in F8IL9-treated compared with control animals, the untreated PH and the MAC group (p < 0.05).

CONCLUSIONS

Beneficial treatment effects of targeted IL9 delivery in a preclinical model of PH could be convincingly validated. IL9-mediated recruitment of Tregs into lung tissue might play a crucial role in the induction of anti-inflammatory and anti-proliferative mechanisms potentially contributing to a novel disease-modifying concept.

Immunophenotypic study of basophils by multiparameter flow cytometry

CONTEXT

The immunophenotypic profile of basophils is not yet fully established, and the immunophenotypic changes in chronic myelogenous leukemia are not fully characterized.

OBJECTIVE

To establish a comprehensive immunophenotypic spectrum of normal basophils and to assess the range of immunophenotypic aberrations of basophils in chronic myelogenous leukemia.

DESIGN

Using 4-color flow cytometry, we compared the immunophenotypic profile of basophils in peripheral blood or bone marrow samples from 20 patients with no evidence of neoplasia to basophils from 15 patients with chronic myelogenous leukemia.

RESULTS

Basophils in control cases were all positive for CD9, CD13, CD22, CD25 (dim), CD33, CD36, CD38 (bright), CD45 (dimmer than lymphocytes and brighter than myeloblasts), and CD123 (bright), and were negative for CD19, CD34, CD64, CD117, and HLA-DR. Basophils in all chronic myelogenous leukemia patients possessed 1 to 5 immunophenotypic aberrancies. The most common aberrancies were underexpression of CD38, followed by aberrant expression of CD64 and underexpression of CD123. CD34 and CD117 were present in cases with basophilic precursors. Myeloblasts showed a distinct immunophenotypic profile, as they typically expressed CD34 and CD117, showed dimmer expression (compared with basophils) of CD38, CD45, and CD123, and lacked expression of CD22.

CONCLUSIONS

Flow cytometric immunophenotyping can identify immunophenotypic aberrations of basophils in chronic myelogenous leukemia, and discriminate basophils from myeloblasts.

Effects of the pathogenic Vibrio tapetis on defence factors of susceptible and non-susceptible bivalve species: I. Haemocyte changes following in vitro challenge

In microbial infections, the interaction between microorganisms and phagocytic cells is a crucial determinant in the outcome of the disease process. We used flow cytometry to study the in vitro interactions between Vibrio tapetis, the bacterium responsible for Brown Ring Disease (BRD) in the Manila clam Ruditapes philippinarum, and haemocytes from three bivalve species: the Manila clam (susceptible to BRD), the hard clam Mercenaria mercenaria and the eastern oyster Crassostrea virginica (both non-susceptible to BRD). Results demonstrated that V. tapetis cells and extracellular products elicit major changes in the haemocytes of R. philippinarum, including decreased viability and phagocytic activity, and altered size and internal structure. V. tapetis was able to kill haemocytes from M. mercenaria and C. virginica but to a far lesser extent than those of R. philippinarum. These results suggest that disease resistance is not solely dependent on a host activity against the pathogen, but is also a function and magnitude of the injury to the host cell by a given pathogen.

In vitro assays for the diagnosis of IgE-mediated disorders

Advances in technology have provided new laboratory tools for the quantitation of allergen-specific IgE antibodies in serum and on the surface of basophils. This review examines the evolution from qualitative IgE antibody assays of the late 1960s to the present-day, third-generation, automated and quantitative allergen-specific IgE assays. The latest technology trend is toward microarrays in which crude or purified native and recombinant allergens can be spotted in microdot arrays on silica chips to permit extensive panels of specific IgE measurements to be performed with small quantities of serum. Although these technologies hold promise, their diagnostic performance requires further assessment once their technical details have been optimized. Potential abuses of this newer IgE antibody technology include the use of allergosorbent specificities (eg, especially food and drugs) that lack validation, application of IgE antibody measurements in the diagnosis of non-IgE-dependent disorders (eg, aspirin sensitivity), and modification of IgE antibody assays to measure food-specific IgG antibody for which there is no clinical indication. Basophil mediator release assays have evolved to include flow cytometric methods that can quantitatively detect the presence of cell surface-bound allergen-specific IgE antibodies. Assays for histamine and leukotriene C 4 released after in vitro basophil activation are now more accurate and standardized. Current analytic methods for IgE antibodies provide more quantitative and reproducible measurements of IgE than ever before, although still with less sensitivity that traditional skin testing. The current challenge is to translate the quantitative IgE antibody results into a more accurate diagnosis of allergic disease.

In vitro allergy diagnosis: should we follow the flow?

During the last 5 years, an increasing number of studies have demonstrated that flow cytometric quantification of in vitro basophil activation can be a quite performant and reliable tool to measure IgE-dependent allergen-specific responses in allergic patients. So far, most assays have used CD63 as a basophil activation marker and native allergen extracts for stimulation. However, other basophil markers and recombinant allergens have recently been introduced. The technique has been applied for the diagnosis of allergy to pollen, house dust mite, food, natural rubber latex, hymenoptera venom and drugs. In addition, the technique has proven to be useful in non-IgE-mediated reactions such as hypersensitivity to drugs as well as detection of auto-antibodies in chronic urticaria. This review will focus on some specific issues: (1) principles of flow cytometric analysis of in vitro-activated basophils, (2) general technical aspects of the technique (including passive sensitization), (3) clinical applications and (4) recommendations for further development and evaluation of the technique.

CD84 expression on human hematopoietic progenitor cells

OBJECTIVE

CD84 is a member of the CD2 subgroup of the immunoglobulin receptor superfamily. Members of this family have been implicated in the activation of T cells and NK cells. Expression of CD84 was originally described on most mononuclear blood cells as well as platelets. To elucidate its presence on other blood cell types, we analyzed the expression pattern of CD84 on human immature CD34+ and mature hematopoietic cells.

METHODS

Expression analysis was carried out by flow cytometry. The differentiation potential of CD84+ progenitor cells was assessed by colony-forming assays and long-term cultures. RT-PCR was used to analyze CD84 mRNA isoforms.

RESULTS

In addition to monocytes, macrophages, B cells, and some T cells, CD84 is expressed on the cell surface of the majority of granulocytes. In addition, 64%+/-5% of CD34+ progenitor cells isolated from peripheral blood and 30.5%+/-5% from bone marrow of healthy volunteers also express CD84. The majority of CD34+ cells coexpressing lineage antigens were CD84+. In methylcellulose CD34+CD84+ cells formed primarily erythroid colonies, whereas myeloid or mixed colonies were scarce. The frequency of long-term culture-initiating cells in peripheral blood was approximately fivefold higher in CD34+CD84- vs CD34+CD84+ cells. In short-term cultures, 95% of the initially CD34+CD84- cells became CD84+ after 72 hours.

CONCLUSIONS

CD84 is expressed on cells from almost all hematopoietic lineages and on CD34+ hematopoietic progenitor cells. The proliferative potential of CD34+ cells decreases with increasing CD84 expression, suggesting that CD84 serves as a marker for committed hematopoietic progenitor cells.

Validation of a two-color flow cytometric assay detecting in vitro basophil activation for the diagnosis of IgE-mediated natural rubber latex allergy

BACKGROUND

IgE-dependent triggering of basophils not only elicits the release of different mediators but also the up-regulation of certain markers, e.g. CD63, which can be detected by flow cytometry. We intended to investigate if flow cytometric analysis of basophil activation could be a valuable tool in the diagnosis of latex allergy, and to evaluate if the basophil activation test (BAT) could be helpful in determining the clinical significance of a positive latex IgE in individuals with negative history and negative latex skin test. Additionally we aimed to determine the role of cross-reactive carbohydrate determinants (CCDs) in causing positive latex IgE without apparent clinical significance.

METHODS

Twelve healthy controls without a history of latex hypersensitivity with a negative latex IgE and skin test (group 1), 24 individuals without a history of latex hypersensitivity with a negative latex IgE and skin test but with other inhalant allergies (group 2), and 29 latex allergic patients with a compelling history of latex allergy with a positive latex IgE and prick test (group 3) were enrolled. The diagnostic performances of the BAT were further evaluated in 13 individuals with a history of latex allergy but with negative specific IgE and/or skin test (group 4). Twenty-four individuals with positive latex IgE without apparent clinical relevance, i.e. without history of latex hypersensitivity and negative latex skin tests, were also analyzed (group 5). The putative role of CCDs causing positive latex IgE results without apparent clinical significance was evaluated by quantification of IgE for bromelain.

RESULTS

According, to the receiver operating characteristics(ROC)-generated threshold value of 17% between latex allergic patients and the pooled group of nonlatex allergic individuals, the sensitivity and specificity of the basophil activation test was 93.1% and 91.7%, respectively. In healthy controls, allergic patients without latex hypersensitivity and latex allergic patients the number of positive BATs was 0/12, 3/24 and 27/29, respectively. In the individuals with an evocative history of latex allergy but with negative latex IgE and/or skin test the BAT was positive in all 13 cases. Twenty of 24 individuals without apparent latex allergy but with positive latex IgE had a negative BAT. IgE for bromelain was positive in 1/19 sera from group 2, 1/24 sera from group 3, none of the 8 sera from group 4, but in 16/18 sera from group 5, respectively.

CONCLUSION

Flow cytometric analysis of activated basophils seems a highly sensitive and specific tool for diagnosing latex allergy. In addition, the technique might help to determine the clinical relevance of positive IgE quantification in the absence of overt latex allergy. CCDs of natural rubber latex allergens were confirmed to mimic latex sensitization.

Systemic activation of basophils and eosinophils: markers and consequences

Basophils and eosinophils are important effector cells in human allergic diseases; they play a significant role in promoting allergic inflammation through the release of proinflammatory mediators (such as histamine, leukotriene C(4), major basic protein, eosinophil cationic protein, IL-4, and IL-13, among others). Notably, in allergic subjects, these cells exist in higher numbers and in a more activated state compared with nonatopic control subjects. Evidence for the greater activation state includes increased expression of intracellular and surface markers and hyperreleasability of allergy mediators. We have been interested in the phenotypic markers of effector-cell activation for many years. There is considerable overlap among activation markers, and few activation markers have been found that define a unique phenotype that is quantifiable in the assessment of the presence and severity of allergic disease. This review summarizes the existing evidence for systemic activation of human basophils and eosinophils in allergic diseases. The potential mechanisms responsible for functional and morphologic alterations in these effector cells and the specificity and utility of surface markers in the assessment of allergic disease activity or severity are also discussed.

The relationship between serum IgE and surface levels of FcepsilonR on human leukocytes in various diseases: correlation of expression with FcepsilonRI on basophils but not on monocytes or eosinophils

BACKGROUND

Expression of receptors for IgE (FcepsilonR) have been mainly studied on mast cells and blood basophils in the context of allergic disease. Some reports have noted limited expression of FcepsilonR on other leukocytes, including blood monocytes and eosinophils in certain patients. An association between human blood basophil expression of FcepsilonRIalpha and serum IgE has been noted among allergic subjects.

OBJECTIVE

Recent evidence supports regulation of FcepsilonRIalpha by free IgE on both mast cells and basophils. We hypothesized that this relationship would exist across an extremely wide range of IgE levels for human basophils, irrespective of underlying disease. We further examined whether a similar relationship existed between serum IgE and FcepsilonRIalpha or FcepsilonRII (CD23) expression on monocytes and eosinophils in these same subjects.

METHODS

Blood was obtained from nonallergic subjects (n = 3) and subjects with allergic asthma (n = 5), atopic dermatitis (n = 3), hypereosinophilic syndromes (n = 7), hyper-IgE syndrome (n = 6), helminth infestation (n = 6), or IgE myeloma (n = 1). Levels of serum IgE were determined by using RIA and ranged from 3 to 4.7 mg/mL. Levels of cell surface FcepsilonRIalpha, FcepsilonRII, and IgE were measured by using immunofluorescence and flow cytometry.

RESULTS

Basophil surface IgE density and FcepsilonRIalpha expression correlated with serum IgE levels (r = 0. 67 and r = 0.46, respectively; P <.01; n = 31) regardless of the disease state. In contrast, monocyte FcepsilonRIalpha expression did not correlate with serum IgE (r = 0.09, P >.5, n = 29), and low-level eosinophil FcepsilonRIalpha expression was only detected in a single asthmatic subject. CD23 expression was not detected on basophils or eosinophils, except for the eosinophils from the donor with IgE myeloma. CD23 was present on monocytes from some donors but did not correlate with serum IgE levels.

CONCLUSIONS

In a variety of disease states, FcepsilonRIalpha expression by basophils, but not monocytes or eosinophils, correlated with serum IgE levels across a 6-log range of IgE. These data support the concept of in vivo regulation of FcepsilonRIalpha on basophils by serum IgE and further demonstrate that this is independent of allergic disease per se.

Immunologically mediated signaling in basophils and mast cells: finding therapeutic targets for allergic diseases in the human FcvarepsilonR1 signaling pathway

The high affinity IgE receptor, FcvarepsilonRI, plays key roles in an array of acute and chronic human allergic reactions including asthma, allergic rhinitis, atopic dermatitis, urticaria and anaphylaxis. In humans and rodents, this receptor is found at high levels on basophils and mast cells where its activation by IgE and multivalent antigen produces mediators and cytokines responsible for FcvarepsilonRI-dependent acute inflammation. Mast cells can additionally contribute to sustained inflammatory responses by internalizing antigen bound to IgE-FcvarepsilonRI complexes for processing to peptides and presentation to T cells. In humans, the FcvarepsilonRI is also expressed, at lower density, on monocytes, macrophages and dendritic cells (DC) where its likely functions again include both signaling to mediator and cytokine production and antigen presentation. Our laboratories have focused on defining the earliest steps in the FcvarepsilonRI signaling cascade in basophils and mast cells and on developing new routes to control allergic inflammation based on inhibiting these events. Here, we describe novel strategies to limit antigen-stimulated FcvarepsilonRI signaling by: (1) sequestering the FcvarepsilonRI-associated protein-tyrosine kinase, Lyn, that initiates FcvarepsilonRI signaling; (2) eliminating; or (3) inactivating the protein-tyrosine kinase, Syk, that propagates FcvarepsilonRI signaling; and (4) establishing inhibitory crosstalk between FcvarepsilonRI and a co-expressed receptor, FcgammaRII, that again limits FcvarepsilonRI-mediated Syk activation. These strategies may form the basis for new therapies for allergic inflammation.