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.

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.

Background: Although characteristics of intraepithelial lymphocytes (IELs) in mucosal immunity have been well defined in the intestine, bronchial IELs have been little investigated. Recently, we showed that bronchial IELs have a distinct function that partly resembles that of intestinal IELs; however, surface antigen expression of bronchial IELs and the relationship of that expression to airway disease have not been studied. Methods: We analyzed phenotypic profiles of human bronchial IELs and lamina propria lymphocytes (LPLs) by double-staining immunohistochemistry using full-thickness bronchial specimens (10 nonasthmatic controls and 7 asthmatics) from lung resections. Results: In controls, the percentage of CD4+ cells was lower, and the percentage of CD8+ cells was higher in IELs compared to LPLs (CD4: median 50.0% in IELs vs. 65.9% in LPLs, p = 0.01; CD8: 50.9% in IELs vs. 34.4% in LPLs, p = 0.007). The percentage of cells positive for CD103 (αE-integrin) was higher in IELs than that in LPLs (median 60.1% in IELs vs. 16.9% in LPLs; p < 0.001). In IELs from asthmatics, these characteristics were particularly significant (CD4: median 26.2%, p = 0.008; CD8: 79.8%, p = 0.007; CD103: 76.2%, p = 0.019; all compared with IELs from nonasthmatics). Conclusions: These results suggest that human bronchial IELs have roles distinct from subsets of other lymphocytes, and that CD8+ cells and CD103+ cells have potentially important functions in the bronchial epithelium.

SummaryIntraepithelial lymphocytes (IELs) can be identified among epithelial cells in systemic mucosal tissues. Although intestinal IELs play a crucial role in mucosal immunity, their bronchial counterparts have not been well studied. The purpose of this study was to determine the immunological functions of human bronchial IELs, which interact directly with epithelial cells, unlike lamina propria lymphocytes (LPLs). We isolated successfully bronchial IELs and LPLs using a magnetic cell separation system from the T cell suspensions extracted from bronchial specimens far from the tumours of resected lungs. Human bronchial IELs showed an apparent type 1 cytokine profile and proliferated more actively in response to CD2 signalling than did bronchial LPLs.

T cells play an important role in the pathogenesis of bronchial asthma. However, it is not completely known how circulating lymphocytes infiltrate into the airways of asthmatic patients. Because SCID mice are unable to reject xenogenic transplants, many xenotransplant models using various human tissues have been developed. Therefore, to examine the interaction between bronchi and T lymphocytes of asthma, it may be possible to use the human bronchial xenograft and PBMC xenograft in SCID mice. We transplanted human bronchi into the subcutaneum of SCID mice and i.p. injected PBMCs that were obtained from patients with atopic asthma, atopic dermatitis and rheumatoid arthritis, and normal subjects (asthmatic, dermatitis, rheumatic, and normal huPBMC-SCID mice). There was no difference in the percentage of CD3-, CD4-, CD8-, CD25-, CD45RO-, CD103-, and cutaneous lymphocyte Ag-positive cells in PBMCs among the patients with asthma, dermatitis, rheumatoid arthritis, and normal subjects, and CD3-positive cells in peripheral blood of asthmatic, dermatitis, rheumatic, and normal huPBMC-SCID mice. The number of CD3-, CD4-, and CD8-positive cells in the xenografts of asthmatic huPBMC-SCID mice was higher than those of dermatitis, rheumatic, and normal huPBMC-SCID mice. IL-4 mRNA and IL-5 mRNA were significantly higher in the xenografts of asthmatic huPBMC-SCID mice than those in the xenografts of normal huPBMC-SCID mice, but there were no significant differences in the expressions of IL-2 mRNA or IFN-γ mRNA between them. These findings suggest that T cells, especially Th2-type T cells, of asthmatics preferentially infiltrate into the human bronchi.