Eosinophil density: what does it mean?

Toward the Proteome of the Human Peripheral Blood Eosinophil

Eosinophils are granular leukocytes that have significant roles in many inflammatory and immunoregulatory responses, especially asthma and allergic diseases. We have undertaken a fairly comprehensive proteomic analysis of purified peripheral blood eosinophils from normal human donors primarily employing 2-dimensional gel electrophoresis with protein spot identification by matrix-assisted laser desorption/ionization mass spectrometry. Protein subfractionation methods employed included isoelectric focusing (Zoom(®) Fractionator) and subcellular fractionation using differential protein solubilization. We have identified 3,141 proteins which had Mascot expectation scores of 10(-3) or less. Of these 426 were unique and non-redundant of which 231 were novel proteins not previously reported to occur in eosinophils. Ingenuity Pathway Analysis showed that some 70% of the non-redundant proteins could be subdivided into categories that are clearly related to currently known eosinophil biological activities. Cytoskeletal and associated proteins predominated among the proteins identified. Extensive protein posttranslational modifications were evident, many of which have not been previously reported that reflected the dynamic character of the eosinophil. This dataset of eosinophilic proteins will prove valuable in comparative studies of disease versus normal states and for studies of gender differences and polymorphic variation among individuals.

Asthma

Asthma has been recognized as a disease since the earliest times. In the Corpus Hippocraticum, Hippocrates used the term “ασθμα” to indicate any form of breathing difficulty manifesting itself by panting. Aretaeus of Cappadocia, a well-known Greek physician (second century A.D.), is credited with providing the first detailed description of an asthma attack [13], and to Celsus it was a disease with wheezing and noisy, violent breathing. In the history of Rome, we find many members of the Julio-Claudian family affected with probable atopic respiratory disorders: Caesar Augustus suffered from bronchoconstriction, seasonal rhinitis as well as a highly pruritic skin disease. Claudius suffered from rhinoconjunctivitis and Britannicus was allergic to horse dander [529]. Maimonides (1136–1204) warned that to neglect treatment of asthma could prove fatal, whereas until the 19th century, European scholars defined it as “nervous asthma,” a term that was given to mean a defect of conductivity of the ninth pair of cranial nerves.

Retrospective study on fluticasone propionate aqueous nasal spray efficacy in patients with allergic rhinitis: evaluation of clinical and laboratory parameters

BACKGROUND

In allergic rhinitis, allergenic stimulation causes the release of various mediators that induce symptoms and the development of chronic inflammation, which, in turn, is caused by cells involved in the late phase of inflammation, such as eosinophils. The eosinophils also cause damage at the mucosal level through the secretion of eosinophil cationic protein and other preformed factors contained in their granules. The objective was to verify the efficacy of fluticasone propionate aqueous nasal spray in patients with allergic rhinitis; in a retrospective study, we have evaluated mediators of inflammation, making correlations with the clinical symptoms score during and outside the pollen season.

METHODS

Forty patients with allergic rhinitis and 15 normal controls were included in our study. Eosinophil cationic protein, eosinophil chemotactic activity, and blood and nasal lavage eosinophil count were evaluated as laboratory parameters.

RESULTS

We found a significant increase in nasal lavage levels of eosinophil cationic protein in allergic patients, and this was strictly correlated with the clinical symptoms score. No differences were found in the eosinophil count of allergic patients and in the serum eosinophil cationic protein of patients sensitized to seasonal allergens in comparison with normal subjects. By contrast, an increase in serum eosinophil cationic protein level was found in patients sensitized to perennial allergens. After topical administration of fluticasone propionate aqueous nasal spray, a reduction in nasal lavage eosinophil cationic protein secretion was obtained with a reduction of eosinophil chemotactic activity at the local level. This reduction correlated with an improvement of clinical symptoms.

CONCLUSIONS

The clinical improvement and reduction in nasal lavage eosinophil cationic protein and eosinophil chemotactic activity after administration of fluticasone propionate aqueous nasal spray further confirms the role of this treatment in allergic rhinitis.

A method to study apoptosis in eosinophils by flow cytometry

The aim of this study was to develop a simple flow cytometric procedure to study eosinophil apoptosis. Eosinophils were isolated from the peripheral blood of healthy, non-allergic individuals and then cultured in basal culture medium. The cells were examined after 24, 48 and 72 h for forward- and side scatter (FS-SSC) pattern, staining with FDA, PI, and anti-CD95, and light microscopic appearance. After culture for >24 h, two populations with different FS-SSC-patterns appeared, referred to as A and B. Population A consisted of living, FDA-positive eosinophils. The eosinophils in population B showed a lower FS scatter than those in population A and a staining pattern with PI indicating the presence of hypodiploid DNA. Anti-CD95 demonstrated a significant staining of the eosinophils in population B, which increased after 2 days in culture. The cells were sorted using a FACS-Scan cell sorter and by Annexin V-coated magnetic beads to permit separate analyses of PI-staining pattern, DNA electrophoresis, and light microscopic examination of the cells in population B. The present study suggest that it is possible to discriminate between apoptotic and living eosinophils using the FS-SSC pattern and the PI-staining pattern obtained by flow cytometry.

Quantitative, rather than qualitative, differences in CD69 upregulation in human blood eosinophils upon activation with selected stimuli

BACKGROUND

The study aimed to investigate whether CD69 expression on granulocytes is subject to specific regulation by inflammatory mediators, and, if so, to identify these factors in relation to eosinophil activity markers such as the EG2 epitope and ECP release.

METHODS

Peripheral blood leukocytes from healthy donors were used. The surface and intracellular distribution of CD69 was investigated with a whole-blood cell-membrane permeabilization technique, the FOG method, and flow cytometry. In vitro stimulation was performed with GM-CSF, IL-5, IL-5 plus eotaxin, LPS, and fMLP.

RESULTS

A preformed intracellular pool of CD69 was demonstrated in both eosinophils and neutrophils, but not in monocytes. Almost no resting eosinophils, neutrophils, or monocytes expressed CD69 on the cell surface. However, in vitro stimulation with selected stimuli increased the proportion of CD69-positive eosinophils to various extents, with GM-CSF being the most and fMLP the least efficient stimulus. The neutrophils did not respond under these conditions. Increased expression of the EG2 epitope and initiation of degranulation preceded CD69 upregulation.

CONCLUSIONS

Eosinophils and neutrophils from healthy donors have a preformed intracellular pool of CD69, which is mobilized on the cell surface on eosinophils, but not on neutrophils, to various extents by selected stimuli. Monocytes, however, do not have a preformed intracellular pool of CD69. Our data indicate that a kinetic order exists among the EG2 expression, the degranulation process, and CD69 upregulation. Due to a quantitative, rather then a qualitative, upregulation of CD69 by stimuli associated with both allergic and bacterial inflammation, CD69 may be a potential activity marker of clinical value.

Conditions in blood sampling procedures that extend the ex vivo stability of eosinophil activity markers in peripheral blood from allergic patients and healthy controls

BACKGROUND

Serum-ECP, EG2-epitope on intracellular ECP and surface expression of CD9 and CD11b in peripheral blood eosinophils (PBE) are considered to be markers that mirror clinical parameters in allergic inflammation.

OBJECTIVE

The aim was to investigate the impact of the blood sampling procedure on PBE markers and to identify optimal conditions for extended pre-analysis storage.

METHODS

Blood, from healthy individuals and patients with allergic rhinitis/asthma, was collected in tubes with EDTA, citrate, or without anti-coagulant. The expression of EG2-epitope, CD9, and CD11b were analyzed in eosinophils and neutrophils after 1, 5, and 24 hours of storage at +4 degrees C, according to the FOG-method and flow cytometry. In vitro stimulation with fMLP/PMA was used for metabolic activity analysis and CD11b mobilization. Following a 1-hour clotting period at +20 to 22 degrees C, samples were stored at +4 degrees C and serum-ECP levels were measured.

RESULTS

The EG2-epitope, serum-ECP, and CD9 were stable in samples from both healthy controls and allergic patients at all storage conditions. The EG2-epitope, serum-ECP and PBE count were significantly increased in the patient group, whereas no differences were observed in the expression of CD9 or CD11b. Both granulocytes and monocytes retained their metabolic activity for 24 hours. Neutrophils in citrate-blood increased their ability to respond to fMLP, as compared with EDTA-blood.

CONCLUSION

In vitro analysis of selected activity markers and functional tests could be performed on granulocytes from both healthy individuals and allergic patients after 24 hours storage at +4 degrees C. The anticoagulant citrate seems to be preferable to EDTA when monocytes or CD11b expression are analyzed.

Eosinophils isolated by magnetic cell sorting respond poorly to lipid chemoattractants

BACKGROUND

Eosinophils play an important role in allergic inflammation. In vitro methods to isolate human eosinophils for the study of chemotactic responses are essential in understanding the mechanisms involved in tissue eosinophilia.

OBJECTIVE

We compared LTB4 and PAF-induced chemotactic responses of eosinophils isolated by the standard Percoll (positive selection) versus the magnetic cell separation systems (MACS) (negative selection) technique.

METHODS

Discontinuous Percoll gradients were preceded by dextran and Ficoll-Paque steps, and followed by gelatin wash and red blood cell (RBC) lysis. MACS isolation included Percoll 1.090 g/mL layering and RBC lysis; incubation with CD16 antibody conjugated to magnetic beads (to bind neutrophils); and isolation of eluate from column positioned in magnet.

RESULTS

Percoll-isolated eosinophils migrated to the lipid mediators, LTB4 and PAF, in a dose-responsive fashion. Although MACS isolation provided a greater number and higher purity of eosinophils, these eosinophils migrated less to LTB4 and PAF. Neither dextran sedimentation, dextran and Ficoll-Paque, nor dextran Ficoll-Paque and Percoll prior to MACS isolation reversed the decreased chemotactic responses observed with MACS isolated eosinophils. Further, Percoll-isolated eosinophils further purified with CD16 MicroBeads did not respond as well to LTB4 or PAF.

CONCLUSIONS

The technique used to isolate eosinophils clearly affects the chemotactic responsiveness of this cell to LTB4 and PAF. Since several in vivo studies suggest that LTB4 and PAF are eosinophil chemoattractants, Percoll isolation of these cells might be more appropriate for studies involving eosinophil chemotactic responses to these lipid mediators.

A microtiter assay for activation of eosinophils. Simultaneous monitoring of eosinophil adhesion and degranulation

A simple microtiter assay for eosinophil activation is described. The assay used 1000-4000 eosinophils/microtiter well, and the design allows for a separate or simultaneous quantitative assessment of eosinophil adhesion to protein-coated microtiter wells and degranulation after stimulation with eosinophil-activating factors. The number of adherent eosinophils is quantified indirectly by expressing the amount of eosinophil cationic protein (ECP) extracted from the adherent fraction of cells in percentage of the total amount of ECP extracted from the cells added to the wells. Degranulation is quantified in the same way by expressing the amount of ECP or eosinophil protein X (EPX) released to the supernatant in percentage of the total amount of ECP or EPX. Known eosinophil-activating agents such as PMA, interleukin (IL)-3, IL-5, GM-CSF, and platelet-activating factor (PAF) all induced a time- and dose-dependent adhesion to albumin-coated wells, whereas L-PAF did not. Kinetic experiments showed that most adhesion occurred within the first 15-30 min, reaching a plateau around 60 min. After prolonged incubation, a decline in adhesion was detected. GM-CSF-induced adhesion was completely inhibited by incubation with monoclonal antibodies directed against the common beta 2-chain (CD18) of the LFA-1, Mac-1, p150,95 complexes. Monoclonal antibodies against CD11a, CD11b, CD11c, VLA-4 ALFA, ICAM-1, VCAM-1, Sialyl-Le(x), ELAM-1, and LECAM had no inhibitory effect. Simultaneous monitoring of adhesion and degranulation after stimulation of eosinophils in albumin-coated wells with either PMA or GM-CSF showed that adhesion always preceded degranulation. Replacing the albumin coating of the microtiter wells with IgG or secretory IgA augmented both the spontaneous and the PMA- or GM-CSF-stimulated responses. In conclusion, the assay allows dynamic evaluation of eosinophil activation and can be used to assess soluble eosinophil-activating factors as well as to study eosinophil activation by solid-phase-bound proteins.