Kita, H.

Abstract CD9 is a cell surface glycoprotein belonging to the transmembrane 4 superfamily. In this report, we demonstrate that cross-linking CD9 with different forms of mAb activates distinct functions of human eosinophils. Anti-CD9 mAb (clone ALB6) immobilized onto tissue culture plates induced eosinophil degranulation. This effect of anti-CD9 mAb (clone ALB6) was unique because other immobilized clones of anti-CD9 mAb (clones FMC56 and ML13) or anti-HLA Class I mAb failed to induce degranulation. In addition, neutrophil degranulation was not provoked by the immobilized clone ALB6, consistent with a lack of expression of CD9 on neutrophils. Eosinophil degranulation induced by anti-CD9 mAb (clone ALB6) was abolished by pretreatment of eosinophils with anti-CD18 mAb, suggesting that beta2 integrins are involved in the reaction. In contrast to the results with immobilized clones, all clones of anti-CD9 mAb in soluble form enhanced eosinophil survival. This enhanced survival was inhibited by anti-granulocyte-macrophage-CSF (GM-CSF) mAb, suggesting that autocrine production of GM-CSF by eosinophils mediated the enhanced survival. In fact, by ELISA and RT-PCR, GM-CSF protein and mRNA were detected in supernatants and cell lysates of eosinophils stimulated by soluble anti-CD9 mAb, but not by immobilized mAb. These results indicate that CD9 serves as a molecule that delivers stimulation signals on eosinophils. The eosinophil's cellular responses may differ and be dependent on the manner of receptor ligation.

Abstract Cellular adhesion plays an important role in the recruitment and activation of eosinophils. Here, we investigated whether extracellular matrix (ECM) proteins modify effector functions of activated human eosinophils. We coated 96-well plates with laminin or fibronectin and blocked nonspecific protein-binding sites with human serum albumin (HSA). When eosinophils were stimulated with platelet-activating factor (PAF) and incubated in these ECM-coated wells, the eosinophils adhered using both β 1- and β 2-integrins. Degranulation of eosinophils adherent to laminin- and fibronectin-coated wells was reduced about 50% compared with cells adherent to uncoated, HSA-blocked wells. Furthermore, these inhibitory effects of laminin and fibronectin were concentration-dependent and secretagogue-specific, that is, degranulation induced by C5a and IL-5 was inhibited while degranulation induced by secretory IgA and PMA was not inhibited. Plasma fibronectin, type I collagen and type IV collagen also inhibited PAF- and C5a-induced eosinophil degranulation, whereas fibrinogen did not. By microscopy, PAF-stimulated eosinophils, adhering to uncoated HSA-blocked wells, appeared elongated with many pseudopods. In contrast, eosinophils adhering to laminin-coated wells appeared oval with few pseudopods. Furthermore, when cells were incubated in laminin-coated wells, PAF-stimulated production of a second messenger, inositol phosphate, was markedly reduced. These findings suggest that ECM protein, such as laminin and fibronectin, attenuate both activation and degranulation of eosinophils and also influence their morphology after stimulation by physiologic secretagogues. Thus, ECM proteins may regulate activation of eosinophils, as they traverse between the peripheral blood and their targets.

Abstract Recent evidence suggests adhesion molecules play an important role in the function of leukocytes. Because human eosinophils are known to express beta 2 integrins, we hypothesized that these adhesion molecules mediate the effector function of eosinophils. Normal human eosinophils incubated in albumin-coated polystyrene plates released granule protein and produced superoxide anion when stimulated with human recombinant granulocyte-macrophage CSF (rGM-CSF), platelet-activating factor (PAF), or PMA. Simultaneous monitoring of eosinophil adhesion and degranulation showed that degranulation was always preceded by cellular adhesion regardless of stimuli. Furthermore, eosinophil degranulation induced by human rGM-CSF and PAF was abolished in suspension culture of the cells when the cell suspensions were gently stirred. To identify the molecules involved in this adhesion-dependent degranulation, we have investigated the effects of mAbs (mAb) against beta 2 integrins. mAb reactive with CD18 markedly inhibited the eosinophil adhesion and degranulation induced by PAF and human rGM-CSF. mAb reactive with CD11b also moderately inhibited the adhesion and degranulation. In contrast, mAb reactive with CD11a slightly enhanced or showed no effect on the adhesion and degranulation by human rGM-CSF or PAF. Superoxide production induced by human rGM-CSF and PAF was also abolished by the treatment of cells with anti-CD18 mAb. mAb against CD11b and CD18 had little effect on degranulation and superoxide production induced by PMA. These results indicate that CD11b/CD18 (Mac-1)-dependent cellular adhesion plays an important role in the degranulation and superoxide production of eosinophils induced by human rGM-CSF and PAF, and that these mechanisms may be employed in vivo where eosinophils contact with stromal cells and/or proteins.

AbstractBackgroundExposure to aeroallergens induces eosinophilic airway inflammation in patients with asthma and allergic airway diseases. The circulating number of eosinophils in peripheral blood is relatively small, leading us to hypothesize that bone marrow needs to be engaged quickly to meet the demands of the tissues.MethodsTo investigate the communication between the lungs and bone marrow, we used acute allergen exposure and airway inflammation models in mice. Gene‐deficient mice and cytokine reporter mice as well as in vitro cell culture models were used to dissect the mechanisms.ResultsNaïve BALB/c mice produced increased numbers of eosinophil precursors and mature eosinophils in the bone marrow when their airways were exposed to a common fungal allergen, Alternaria alternata. Expression of IL‐5 and IL‐33 increased rapidly in the lungs, but not in the bone marrow. Sera from allergen‐exposed mice promoted eosinophilopoiesis in bone marrow cells from naïve mice, which was blocked by anti‐IL‐5 antibody. Mice deficient in the IL‐33 receptor ST2 (i.e., Il1rl1−/− mice) were unable to increase their serum levels of IL‐5 and allergen‐induced eosinophilopoiesis in the bone marrow after allergen exposure. Finally, group 2 innate lymphoid cells (ILC2s) in the lungs showed robust expression of IL‐5 after Alternaria exposure.ConclusionsThese finding suggests that lung IL‐33, through innate activation of ILC2s and their production of IL‐5, plays a key role in promoting acute reactive eosinophilopoiesis in the bone marrow when naïve animals are exposed to airborne allergens. Therefore, bone marrow eosinophilopoiesis may be affected by atmospheric environmental conditions.

Abstract Background Innate lymphoid cells ( ILC s) play important roles in innate immunity and tissue remodeling via production of various cytokines and growth factors. Group 2 ILC s ( ILC 2s) were recently shown to mediate the immune pathology of asthma even without adaptive immunity. However, little is known about possible interactions between ILC 2s and other immune cells. We sought to investigate the capacity of ILC 2s to regulate effector functions of T cells. Methods We isolated ILC 2s from the lungs of naïve mice. We cultured CD 4 + T cells with ILC 2s in vitro and examined the functions of these cell types. The mechanisms were investigated using blocking antibodies and cells isolated from cytokine‐deficient mice. For the in vivo study, we adoptively transferred ILC 2s and CD 4 + T cells into Il7ra −/− mice and subsequently exposed the mice to ovalbumin and a cysteine protease. Results Lung ILC 2s enhanced CD 4 + T‐cell proliferation and promoted production of type 2 cytokines in vitro . The interaction between ILC 2s and CD 4 + T cells involved costimulatory molecule OX 40L and cytokine IL ‐4, which was mainly derived from ILC 2s. Adoptive transfer of both ILC 2 and CD 4 + T‐cell populations, but not each population alone, into Il7ra −/− mice resulted in induction of a robust antigen‐specific type 2 cytokine response and airway inflammation. Conclusion Lung ILC 2s function to promote adaptive immunity in addition to their established roles in innate immunity. This novel function of ILC 2s needs to be taken into account when considering the pathophysiology of asthma and other allergic airway diseases.

Abstract Chronic eosinophilic pneumonitis (CEP) is characterized by longstanding respiratory symptoms accompanied by a massive pulmonary eosinophil infiltration. We hypothesized that cytokine(s) produced in the disease sites are implicated in the pathophysiology of CEP. We studied peripheral blood and bronchoalveolar lavage fluids (BALF) obtained from two lung segments of a patient with CEP. Seventy times more eosinophils were found in the BALF from an involved lung segment (showing patchy opacification on a chest roentgenogram) than from an uninvolved segment. The eosinophil-active cytokines interleukin-5 (IL-5), IL-6, and IL-10 were strikingly elevated in the BALF from the involved lung segment, whereas no or minimal levels of these cytokines were detectable in the BALF from the uninvolved segment or serum, respectively. Leukocytes in the involved lung segment, but not those in peripheral blood, expressed messenger ribonucleic acid (mRNA) for IL-5, IL-6, and IL-10. In contrast, IL-2, IL-3, IL-4, interferon-gamma (IFN-gamma), granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor-alpha (TNF-alpha) were not detected in any sample. These findings suggest that increased production of several cytokines, such as IL-5, IL-6, and IL-10, in the involved lung segment, but not in the uninvolved lung segment or peripheral blood, is a critical pathophysiologic feature of CEP.