Eosinophils, allergy and parasites

Basic science and pathophysiology of ocular allergy

Ocular allergy includes several clinical subtypes ranging from the mild seasonal allergic conjunctivitis to the potentially sight-threatening atopic keratoconjunctivitis. Current therapies, particularly for the severe forms of disease, need to be more localized and with fewer side effects. For this to be achieved, it requires a better understanding of the basic mechanisms involved. In this chapter, recent findings are discussed that suggest that it is important to take an integrated approach, including both immune and structural elements of the eye. This provides potential new strategies for therapy, addressing the influence of structural cells in disease. These might influence the immune processes that take place and, as the structural cells are precisely localized, topical application is likely to be effective.

Heterogeneity of expression of IgA receptors by human, mouse, and rat eosinophils

IgA is the most abundant class of Abs at mucosal surfaces where eosinophils carry out many of their effector functions. Most of the known IgA-mediated functions require interactions with IgA receptors, six of which have been identified in humans. These include the IgA FcR FcalphaRI/CD89 and the receptor for the secretory component, already identified on human eosinophils, the polymeric IgR, the Fcalpha/muR, asialoglycoprotein (ASGP)-R, and transferrin (Tf)R/CD71. In rodents, the existence of IgA receptors on mouse and rat eosinophils remains unclear. We have compared the expression and function of IgA receptors by human, rat, and mouse eosinophils. Our results show that human eosinophils express functional polymeric IgR, ASGP-R, and TfR, in addition to CD89 and the receptor for the secretory component, and that IgA receptors are expressed by rodent eosinophils. Indeed, mouse eosinophils expressed only TfR, whereas rat eosinophils expressed ASGP-R and CD89 mRNA. These results provide a molecular basis for the differences observed between human, rat, and mouse regarding IgA-mediated immunity.

IL-9 protects against bleomycin-induced lung injury: involvement of prostaglandins

IL-9 is a Th2 cytokine that exerts pleiotropic activities, and might be involved in the regulation of lung inflammatory processes. To characterize the activity of IL-9 on lung injury, we compared the pulmonary responses to bleomycin (blm) in IL-9 transgenic (Tg5) and wild-type (FVB) mice. Following intratracheal instillation of lethal doses of blm, the mortality rate was markedly reduced in Tg5 mice compared to their wild-type counterparts (ie, 25% mortality for Tg5 versus 85% for FVB mice, 21 days after instillation of 0.05U blm/mouse). Histological and biochemical analyses showed that blm induced less lung injury and less epithelial damage in Tg5 as compared to FVB animals. This protection of Tg5 mice was accompanied by an expansion of eosinophils and B cells in the lungs. In addition, TGF-beta and prostaglandin-E2 (PGE2) levels in broncho-alveolar lavage fluid were also increased in transgenic mice. The contribution of B cells and eosinophils to the protective mechanism did not appear essential since eosinophil-deficient (IL-5 KO) and B-deficient (muMT) mice overexpressing IL-9 were also resistant to high doses of blm. We could rule out that TGF-beta was a key factor in the protective effect of IL-9 by blocking this mediator with neutralizing antibodies. Indomethacin treatment, which inhibited PGE2 production in both strains, suppressed the protection in Tg5 mice, supporting the idea that IL-9 controls blm-induced lung injury through a prostaglandin-dependent mechanism.

Mast Cells, Basophils, and Eosinophils Acquire Constitutive IL-4 and IL-13 Transcripts during Lineage Differentiation That Are Sufficient for Rapid Cytokine Production

Mast cells, basophils, and eosinophils are myeloid cells that are distinguished by their capability to produce IL-4 and IL-13. However, it is not clear how this potential is related to the lineage differentiation of these subsets. In the present study we used bicistronic IL-4 reporter (4get) mice to directly visualize IL-4 expression by nonlymphoid cells in vitro and in vivo at the single-cell level. Our data show that frequent expression of both Il4 alleles is initiated and maintained during ontogeny by an IL-4Ralpha- or Stat6-independent mechanism. Despite the constitutive presence of cytokine transcripts in differentiated cells under steady state conditions, cytokine production is not detectable in the absence of stimulation. Moreover, mature mast cells, basophils, and eosinophils also constitutively express IL-13. Both preformed IL-4 and IL-13 mRNAs are sufficient for rapid cytokine production upon stimulation. Our data show that mast cells, basophils, and eosinophils are programmed for IL-4 and IL-13 expression early in ontogeny. These novel findings have important implications for the prevention and therapeutic intervention of allergic and asthmatic diseases.

Interleukin (IL) 5 levels and eosinophilia in patients with intestinal parasitic diseases

AIM

Intestinal parasitic diseases are commonly accompanied with diarrhoeal symptoms and allergic reactions. Eosinophilia occurs as a result of IL-5 synthesized from Th2 cells during allergic reactions. IL-5 acts as a factor activating eosinophils. The aim of this study was to compare the IL-5 cytokine measurements in serum samples and cell cultures. And also to compare eosinophilia observed in helminth infections and protozoon infections accompanied with allergy.

METHODS

Twenty-three patients who presented with diarrhoeal symptoms and allergic complaints were tested positive for intestinal parasites, as well as 21 controls with allergic complaints who did not have any intestinal parasites were included in this study. IL-5 production in in vitro cell cultures prepared by using phytohemaglutinin (PHA) to stimulate peripheral blood mononuclear cells (PBMC) obtained from the blood samples taken from these patients were compared with the IL-5 level in serum. Furthermore, the IL-5 production in protozoon and helminth infections was also compared. Absolute eosinophil values in 1 mm(3) of blood were calculated by means of peripheral smear in both groups within the scope of the study.

RESULTS

Parasites such as helminth detected in 15 (65.2%) and protozoon in 8 (34.8%) of the patients were included in this study. As regards the values of the sera in both patients with parasite infection and controls, the IL-5 production was found to be higher in the cell culture supernatant (P<0.001 and P<0.05). When the IL-5 level of the patients with helminth parasites was compared with that of those with protozoon, it was determined that the IL-5 level in serum was more significant in the patients with protozoon than in those with helminth (P<0.05). In the study group, the patients were found to have parasites, the percentage of eosinophil was 7.0% compared to 6.5% in the control group. Thus, there was no significant difference between the eosinophil values (P>0.05).

CONCLUSION

It was found that IL-5 cytokine levels in serum samples from the patients with helminth and protozoon displayed more measurable values as compared to the IL-5 levels after stimulation with mitogen. It is concluded that IL-5 acts as a triggering factor in the toxiallergic complaints commonly seen in helminth and protozoon infections.

Characterization of biological activities of feline eosinophil granule proteins

OBJECTIVE

To characterize eosinophil granule-derived proteins in cats.

SAMPLE POPULATION

Eosinophils collected via peritoneal lavage from 2 cats.

PROCEDURE

The cats were infested orally with Toxocara canis eggs and subsequently challenge-exposed with T. canis antigen injected IP to induce peritoneal eosinophilia; eosinophils were collected via peritoneal lavage. Eosinophil granule proteins were acid-extracted, separated by gel-filtration chromatography, and examined for their peroxidase, ribonuclease, and bactericidal activities; the N-terminal sequence of some of these proteins was determined and compared with homologue proteins from other species.

RESULTS

3 protein peaks were separated in the chromatogram. The first peak had both peroxidase and bactericidal activities. The second peak had ribonuclease and bactericidal activities, and the N-terminal sequence of the major protein was homologous with that of proteins of the ribonuclease A superfamily, including eosinophil ribonucleases from humans and other animal species. The third protein peak had bactericidal activity, and the N-terminal sequence of the major protein was homologous with that of human and murine major basic proteins.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that feline eosinophil granules contain major basic protein and eosinophil-associated ribonuclease and the granule proteins have peroxidase, ribonuclease, and bactericidal activities. In cats, characterization of eosinophil granule proteins may be useful in elucidation of the mechanism of tissue damage in eosinophil-associated diseases and development of new treatment options for those diseases. In addition, the identification of conserved structure and function of eosinophil granule proteins in cats is relevant from an evolutionary viewpoint.

Eosinophils and atopic dermatitis

In spite of the progress regarding the description of immunological phenomena associated with atopic dermatitis (AD), the pathogenesis of this disease still remains unclear. The presence of eosinophils in the inflammatory infiltrate of AD has long been established. Eosinophil numbers as well as eosinophil granule protein levels in peripheral blood are elevated in most AD patients and appear to correlate with disease activity. Moreover, eosinophil granule proteins, which possess cytotoxic activity, are deposited in the skin lesions. These observations indicate a role of eosinophils in the pathogenesis of AD. Furthermore, AD is associated with increased production of T helper 2 cytokines including interleukin (IL)-5, which specifically acts on eosinophils, resulting in accelerated eosinophilopoiesis, chemotaxis, cell activation, and delayed apoptosis. Therefore, IL-5 is an interesting target for experimental therapy in this inflammatory disorder of the skin. Such studies might result in new insights into the pathogenetic role of eosinophils in AD.

Eosinophils and T lymphocytes possess distinct roles in bleomycin-induced lung injury and fibrosis

Leukocyte infiltration is characteristic of lung injury and fibrosis, and its role during tissue repair and fibrosis is incompletely understood. We found that overexpression of IL-5 in transgenic mice (IL-5(TG)) or by adenoviral gene transfer increased bleomycin (blm)-induced lung injury, fibrosis, and eosinophilia. Surprisingly, blm-treated IL-5-deficient (IL-5(-/-)) mice also developed pronounced pulmonary fibrosis but characterized by marked T lymphocyte infiltration and absence of eosinophilia. In both murine strains however, induction of lung TGF-beta expression was evident. Purified lung eosinophils from blm-treated IL-5(TG) mice stimulated alpha-smooth muscle actin and collagen expression in mouse lung fibroblasts, without affecting proliferation. Furthermore instillation of purified eosinophils into murine lungs resulted in extension of blm-induced lung fibrosis, thus confirming a role for eosinophils. However, lung T lymphocytes from blm-treated IL-5(-/-) mice were able to stimulate fibroblast proliferation but not alpha-smooth muscle actin or collagen expression. Blocking T cell influx by anti-CD3 Abs abrogated lung fibrosis, thus also implicating T lymphocytes as a key participant in fibrosis. Pulmonary fibrosis in IL-5(TG) mice was preferentially associated with type 2 cytokines (IL-4 and IL-13), whereas fibrotic lesions in IL-5(-/-) animals were accompanied by proinflammatory cytokine (TNF-alpha, IL-1beta, and IFN-gamma) expression. We suggest that eosinophils and T cells contribute distinctly to the development of blm-induced lung fibrosis potentially via their production of different cytokine components, which ultimately induce TGF-beta expression that is intimately involved with the fibrosis.

Correlated evolution between host immunity and parasite life histories in primates and oxyurid parasites

Maturation time is a pivotal life-history trait of parasitic nematodes, determining adult body size, as well as daily and total fecundity. Recent theoretical work has emphasized the influence of prematurational mortality on the optimal values of age and size at maturity in nematodes. Eosinophils are a family of white blood cells often associated with infections by parasitic nematodes. Although the role of eosinophils in nematode resistance is controversial, recent work has suggested that the action of these immune effectors might be limited to the larval stages of the parasite. If eosinophils act on larval survival, one might predict, in line with theoretical models, that nematode species living in hosts with large eosinophil numbers should show reduced age and size at maturity. We tested this prediction using the association between the pinworms (Oxyuridae, Nematoda) and their primate hosts. Pinworms are highly host specific and are expected to be involved in a coevolutionary process with their hosts. We found that the body size of female parasites was negatively correlated with eosinophil concentration, whereas the concentration of two other leucocyte families-neutrophils and lymphocytes-was unrelated to female body size. Egg size of parasites also decreased with host eosinophil concentration, independently of female size. Male body size was unrelated to host immune parameters. Primates with the highest immune defence, therefore, harbour small female pinworms laying small eggs. These results are in agreement with theoretical expectations and suggest that life histories of oxyurid parasites covary with the immune defence of their hosts. Our findings illustrate the potential for host immune defence as a factor driving parasite life-history evolution.

The stimulus-dependent release of eosinophil cationic protein and eosinophil protein x increases in apoptotic eosinophils

Apoptotic cells are regarded as inert bodies that turn off intracellular processes and functional abilities. To study the changes in the ability of eosinophils to release their granule proteins while undergoing apoptosis. Eosinophils were cultured for up to 72 h. Living cells were separated from the apoptotic cells and their release of eosinophil cationic protein (ECP) and eosinophil protein X (EPX) was measured in response to serum-opsonized sephadex particles and phorbol 12-myristate 12-acetate (PMA). Changes in cell structure were examined by electron microscopy, and surface receptor expression of beta1- and beta2-integrins was investigated by flow cytometry. Stimulus-dependent release of the granule proteins ECP and EPX was found to increase in apoptotic eosinophils, whereas surface expression of beta1- and beta2-integrins was downregulated. Ultrastructural examination revealed that the granules of apoptotic eosinophils were translocated to the periphery of the cell, just beneath the plasma membrane. Apoptotic eosinophils are able to release their toxic granule proteins, which is probably because of the rearrangement of the cytoskeleton and spontaneous translocation of granules to the membrane. Our results suggest that apoptotic eosinophils are potentially harmful cells that have retained their ability to react to certain extracellular stimuli. The findings point to unexpected consequences of eosinophil apoptosis.

The biology of IGE and the basis of allergic disease

Allergic individuals exposed to minute quantities of allergen experience an immediate response. Immediate hypersensitivity reflects the permanent sensitization of mucosal mast cells by allergen-specific IgE antibodies bound to their high-affinity receptors (FcepsilonRI). A combination of factors contributes to such long-lasting sensitization of the mast cells. They include the homing of mast cells to mucosal tissues, the local synthesis of IgE, the induction of FcepsilonRI expression on mast cells by IgE, the consequent downregulation of FcgammaR (through an insufficiency of the common gamma-chains), and the exceptionally slow dissociation of IgE from FcepsilonRI. To understand the mechanism of the immediate hypersensitivity phenomenon, we need explanations of why IgE antibodies are synthesized in preference to IgG in mucosal tissues and why the IgE is so tenaciously retained on mast cell-surface receptors. There is now compelling evidence that the microenvironment of mucosal tissues of allergic disease favors class switching to IgE; and the exceptionally high affinity of IgE for FcepsilonRI can now be interpreted in terms of the recently determined crystal structures of IgE-FcepsilonRI and IgG-FcgammaR complexes. The rate of local IgE synthesis can easily compensate for the rate of the antibody dissociation from its receptors on mucosal mast cells. Effective mechanisms ensure that allergic reactions are confined to mucosal tissues, thereby minimizing the risk of systemic anaphylaxis.

Peroxisome proliferator-activated receptors alpha and gamma down-regulate allergic inflammation and eosinophil activation

Allergic asthma is characterized by airway hyperresponsiveness, eosinophilia, and mucus accumulation and is associated with increased IgE concentrations. We demonstrate here that peroxisome proliferator-activated receptors (PPARs), PPAR-alpha and PPAR-gamma, which have been shown recently to be involved in the regulation of various cell types within the immune system, decrease antigen-induced airway hyperresponsiveness, lung inflammation, eosinophilia, cytokine production, and GATA-3 expression as well as serum levels of antigen-specific IgE in a murine model of human asthma. In addition, we demonstrate that PPAR-alpha and -gamma are expressed in eosinophils and their activation inhibits in vitro chemotaxis and antibody-dependent cellular cytotoxicity. Thus, PPAR-alpha and -gamma (co)agonists might be of therapeutic interest for the regulation of allergic or inflammatory reactions by targeting both regulatory and effector cells involved in the immune response.

Apoptotic eosinophils express IL-2R chains alpha and beta and co-stimulatory molecules CD28 and CD86

BACKGROUND

IL-2 and the IL-2 receptor are most commonly connected to lymphocytes and the proliferation of T-cells. In addition, the co-stimulatory molecules CD28, CD86 and CD40 are associated to lymphocytes and antigen processing. Under certain conditions, eosinophils are also able to express these antigens on their surface.

OBJECTIVE

In this study we explored the apoptotic mechanisms by looking for a surface expression on eosinophils exclusive to apoptosis.

METHODS

Flow cytometry analysis was performed on fresh and cultured isolated eosinophils from healthy blood donors and allergic patients. The cells were cultured up to 72 h and then incubated with monoclonal antibodies toward cell surface antigens.

RESULTS

After culture, the apoptotic eosinophils, but not the viable cells, expressed CD25, CD122, CD28 (B7-ligand) and CD86 (B7-2). The expression of CD9, a common eosinophil marker, was maintained on viable cells, but absent on the apoptotic eosinophils. Addition of IL-2 to the culture did not influence the viability of the cells.

CONCLUSION

Our data suggest that apoptotic eosinophils have a unique signalling system and might function in ways different from the role of the living eosinophil. The apoptotic eosinophil expresses markers that indicate communication with lymphocytes and antigen-presenting cells.

Taenia solium metacestode antigens which are protective for pigs induce Th1/Th2 mixed responses in mice

The purpose of this study was to determine the Th1 and Th2 cytokine responses induced by Taenia solium metacestode antigens in mice and correlate them with the immune responses elicited in vivo. To assess this aim, mice were inoculated with metacestode antigens. RNA was obtained from spleen cells of immunized or control mice incubated with metacestode antigens and used to determine the cytokine profile. Peripheral blood eosinophilia was measured daily in each mouse and specific serum antibody levels were determined. Results showed that metacestode antigens induce the synthesis of IL-4, IL-5 and IFN-gamma mRNAs in spleen cells. They also induced peripheral blood eosinophilia and elicited specific IgE and IgG antibodies, especially IgG1. Three antigens were recognized by all IgG subclasses and by IgE (104, 88 and 7 kDa), and a 57-kDa protein was recognized by IgG1, IgG2a, IgG2b, and IgE. IgG1 and IgG2b recognized 52, 30 and 20 kDa antigens. Immune responses elicited in vivo and the cytokine profile showed good correlation.

Recurrent Eosinophilic Mastitis

Systemic diseases rarely present with manifestations in the breast. Disorders such as sarcoidosis and pyoderma gangrenosum have been described to produce signs and symptoms in the breast. Peripheral eosinophilia is a systemic disease associated with a finite group of conditions including asthma, allergic or atopic disease, collagen vascular disease, and parasitic infection. In addition it has been described in association with several malignancies. A 50-year-old woman with a history of asthma and significant eosinophilia presented with an enlarging breast mass. Complete excision of the mass revealed eosinophilic mastitis. Two years later the patient again presented with a large mass in the same breast. Repeat excision demonstrated the same pathology. The clinical significance of this lesion is important because it presents as an enlarging, painless, dominant mass. Excision is necessary for management and to conclusively rule out malignancy. Its recurrence despite excision to negative margins, however, may indicate that control of the eosinophilia—and possibly the underlying disorder—is important to prevent further recurrence.

Human platelets produce granulocyte-macrophage colony-stimulating factor and delay eosinophil apoptosis

An association between eosinophils and platelets has been described in several diseases, most notably asthma. Although the mechanisms through which platelets influence eosinophil behavior are not well defined, platelets seem to contribute to the selective accumulation of eosinophils at sites of allergic inflammation by virtue of their ability to produce eosinophil chemotactic factors. We report here for the first time that platelets delay apoptosis, thus enhancing eosinophil survival. A marked inhibition of spontaneous apoptosis was observed using eosinophil:platelet ratios of 1:50, 1:25, 1:10, and 1:5. Moreover, promotion of eosinophil apoptosis by either pronase or dexamethasone was also inhibited greatly in the presence of platelets. The antiapoptotic effect mediated by platelets was dependent on the release of soluble products and was significantly inhibited by neutralizing antibodies directed to GM-CSF. Studies performed by flow cytometry, directed to analyze the cellular source of this cytokine, demonstrated that intracytoplasmic GM-CSF is present in resting platelets. Moreover, GM-CSF was found in platelet supernatants, at concentrations able to prevent eosinophil apoptosis. Our findings support a novel mechanism through which platelets may contribute to eosinophil accumulation at allergic inflammatory sites.

IgE(+), Kit(-), I-A/I-E(-) myeloid cells are the initial source of Il-4 after antigen challenge in a mouse model of allergic pulmonary inflammation

BACKGROUND

IL-4 is generated within hours after antigen lung challenge and influences events that take place early in the induction of pulmonary inflammation. However, the cells responsible for this early IL-4 production in the lung are unknown.

OBJECTIVES

We sought to characterize the initial inflammatory events in the lung after antigen challenge and to identify cells responsible for producing IL-4 at early time points.

METHODS

Mice were sensitized with ovalbumin or passive IgE and challenged intranasally. Histologic measures of inflammation were used, and lung tissue cytokine production was analyzed by means of RT-PCR. Cells producing IL-4 were characterized by means of in situ hybridization and flow cytometry.

RESULTS

IL-4 mRNA was detectable 100 minutes after challenge in sensitized animals. Blockade of this early IL-4 downregulated vascular cell adhesion molecule 1 mRNA expression and attenuated the early recruitment of eosinophils to the lung. CD4-depleted and mast cell-deficient mice both expressed early IL-4. Cellular analysis revealed the presence of IL-4 protein at 100 minutes exclusively in IgE(+) myeloid cells that did not express CD3, Kit, or I-A/I-E. Moreover, IL-4 production induced by means of passive IgE sensitization and abrogated in FcR gamma-chain-deficient mice supports the conclusion that this IL-4 production is dependent on IgE/gamma-chain interaction.

CONCLUSION

IL-4 production by an IgE/gamma-chain-dependent mechanism occurs rapidly after allergen challenge. At these early time points, IL-4 is produced by a myeloid cell with the characteristics of a mouse basophil (IgE(+), Kit(-), I-A/I-E(-)). These data thus suggest that strategies targeting basophils should be considered in the treatment of early lung inflammation.

The immunobiology of schistosomiasis

Schistosomes are parasitic worms that are a prime example of a complex multicellular pathogen that flourishes in the human host despite the development of a pronounced immune response. Understanding how the immune system deals with such pathogens is a daunting challenge. The past decade has seen the use of a wide range of new approaches to determine the nature and function of the immune response to schistosomes. Here, we attempt to summarize advances in our understanding of the immunology of schistosomiasis, with the bulk of the review reflecting the experimental focus on Schistosoma mansoni infection in mice.

The future of antigen-specific immunotherapy of allergy

More than 25% of the population in industrialized countries suffers from immunoglobulin-E-mediated allergies. The antigen-specific immunotherapy that is in use at present involves the administration of allergen extracts to patients with the aim to cure allergic symptoms. However, the risk of therapy-induced side effects limits its broad application. Recent work indicates that the epitope complexity of natural allergen extracts can be recreated using recombinant allergens, and hypoallergenic derivatives of these can be engineered to increase treatment safety. It is proposed that these modified molecules will improve the current practice of specific immunotherapy and form a basis for prophylactic vaccination.