Background: There is no information whether galectin-9 (a novel eosinophil chemoattractant) was associated with pathogenesis of eosinophilic disorders. Methods: We assessed the expression of galectin-9 with imunostaining and in situ hybridization both in the lesion of angiolymphoid hyperplasia with eosinophilia, and peripheral blood eosinophils of eosinophilic patients (E-Eos) in comparison with those of normal volunteers (N-Eos). Regulation of expression of galectin-9 on eosinophils and the effect of galectin-9 on apoptosis of eosinophil were also evaluated. Results: Many eosinophils infiltrating the site were positive for galectin-9. Surface and intracellular immunoreactive galectin-9 was more evident in E-Eos than N-Eos. When eosinophils were cultured with IL-5 in vitro, the surface galectin-9 expression of E-Eos was significantly downregulated, although that of N-Eos was not affected. Treatment of eosinophils with dexamethasone or anti-Fas antibody significantly upregulated the surface galectin-9 expression of E-Eos. In contrast, dexamethasone partially downregulated the surface galectin-9 of N-Eos, although anti-Fas antibody failed to affect on the surface galectin-9 expression. We also found that recombinant galectin-9 significantly suppressed apoptosis of E-Eos (p = 0.0431), whereas it apparently enhanced apoptosis of N-Eos (p = 0.0173). Furthermore, dexamethasone-induced apoptosis of N-Eos was significantly suppressed by galectin-9 (p = 0.0431), whereas galectin-9 failed to induce significant change in dexamethasone-induced apoptosis of E-Eos. In contrast, apoptosis induced by anti-Fas antibody in both N-Eos (p = 0.0431) and E-Eos (p = 0.0431) was enhanced by galectin-9. Conclusions: These findings suggested that galectin-9 was produced by eosinophils, and galectin-9 showed heterogeneous effects and kinetics to eosinophils, and this factor might be one of crucial factors in eosinophilic inflammation.

Gal-9 attenuates ALI by expanding CD14(-)CD11b(+)Gr-1(+) pDC-like macrophages by preferentially suppressing macrophage functions to release proinflammatory cytokines through TLR4 and TLR2 down-regulation.

To study the mechanisms contributing to the recruitment of a selective leukocyte subset in allergic inflammation involving the airways as may occur in asthma, we examined whether allergic exposure induces the expression of cell adhesion molecules (CAMs) on the bronchial endothelium of passively sensitized human bronchi. Human bronchial tissue obtained from patients undergoing lung cancer surgery was passively sensitized with serum from patients with atopic asthma who were sensitive to house dust mite. We incubated the tissues for 30, 120, 240, and 480 min in the presence or absence of the dust mite allergen. The tissues were stained immunohistochemically for intercellular adhesion molecule 1 (ICAM-1), E-selectin, and vascular cell adhesion molecule 1 (VCAM-1). ICAM-1 was constitutively expressed in both the epithelium and endothelium in all tissues but after allergen stimulation significantly increased at 240 and 480 min. E-selectin expression also existed constitutively and increased significantly at 120 and 240 min with allergen exposure. The constitutive expression of VCAM-1 was less than that of ICAM-1 and E-selectin. Following allergen exposure, VCAM-1 expression increased significantly at 30, 120, 240, and 480 min, and at 480 min reached an almost 3.5-fold increase from baseline expression. The TNF-alpha level in the supernatants significantly increased at 120 min after allergen stimulation, and the interleukin (IL)-1beta level increased in 4 of 15 samples. We also examined the induction of CAMs by TNF-alpha, IL-1beta, and IL-4 on human bronchial tissue. TNF-alpha and IL-1beta increased the expression of ICAM-1, E-selectin, and VCAM-1, whereas IL-4 induced only that of VCAM-1. In addition, neutralizing antibody against TNF-alpha and IL-1beta partially blocked the upregulation of CAMs on passively sensitized bronchial tissue after allergen exposure. Thus, both an IgE-dependent allergic response and selected cytokines are able to upregulate endothelial CAMs in human bronchial tissue. These observations provide further evidence that leukocyte infiltration into the site of allergic inflammation as occurs in atopic asthma is in part regulated by the expression of ICAM-1, VCAM-1, and E-selectin.

Intestinal intraepithelial T lymphocytes (i-IELs) show features different from those of conventional T cells and play specific roles in the mucosal immunity. To investigate whether human bronchial intraepithelial T lymphocytes (IELs) are a distinct entity, we examined T cells in human bronchial xenografts transplanted on mice with severe combined immune deficiency (SCID). We transplanted human bronchi subcutaneously into mice with SCID, resected the xenografts after various incubation periods (7-174 d), and examined them for CD3(+), CD4(+), CD8(+), and CD45(+) cells by immunohistochemistry. The number of CD3(+) cells in the lamina propria decreased significantly in the first month (from 308.7 +/- 60.2 to 70.9 +/- 49. 4/mm(2); P < 0.05), and xenografts more than 5 mo of age had scant T cells in the lamina propria (5.2 +/- 2.0/mm(2)). However, there was no significant difference between the number of CD3(+) IELs in freshly isolated bronchi and in xenografts maintained for more than 5 mo. In freshly isolated bronchi, the number of CD4(+) IELs was significantly lower than that of CD8(+) cells (2.35 +/- 0.62 versus 4.56 +/- 1.32/mm basement membrane; P < 0.01). After transplantation, the mean CD4-to-CD8 ratio of all xenografts was significantly higher than that of freshly isolated bronchi (5.2 +/- 0.9 versus 0.6 +/- 0.2; P < 0.005). The IELs were positive for CD45, which is specific for human leukocytes, and they were eliminated by irradiation before the transplantation. Almost all IELs (99.5%) in the xenografts expressed alphabeta T-cell receptor, and 35.8% of IELs expressed alpha(e)beta7 integrin. Bronchial epithelial cells in the xenografts expressed interleukin (IL)-7, stem cell factor, intercellular adhesion molecule (ICAM)-1, and human leukocyte antigen-DR (HLA-DR). We conclude that in the SCID-Hu chimera model, human bronchial IELs survive for more than 5 mo, unlike the T cells in the lamina propria, and we suggest that human bronchial IELs may be stimulated by bronchial epithelial cells expressing IL-7, stem cell factor, ICAM-1, and HLA-DR.

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