NKG2D ligand expression in Crohn's disease and NKG2D-dependent stimulation of CD8+ T cell migration.

Interaction between the activating NKG2D receptor on lymphocytes and its ligands MICA, MICB, and ULBP1-6 modulate T and NK cell activity and may contribute to the pathogenesis of Crohn's disease (CD). NKG2D ligands are generally not expressed on the cell surface of normal, non-stressed cells, but expression of MICA and MICB in CD intestine has been reported. In this exploratory study, we further characterize the expression of NKG2D and its ligands, including the less well-described ULBP4-6, in CD, and test if NKG2D ligand interactions are involved in the migration of activated T cells into the affected mucosal compartments. Intestinal tissue from CD patients and healthy controls were analyzed by flow cytometry, mass cytometry, and immunohistochemistry for expression of NKG2D and ligands, and for cytokine release. Furthermore, NKG2D-dependent chemotaxis of activated CD8+ T cells across a monolayer of ligand-expressing human intestinal endothelial cells was examined. Activated lymphocytes down-regulated NKG2D expression upon accumulation in inflamed CD intestine. NKG2D expression on CD56+ T and γδ T cells from inflamed tissue seemed inversely correlated with CRP levels and cytokine release. B cells, monocytes, mucosal epithelium, and vascular endothelium expressed NKG2D ligands in inflamed CD intestine. The expression of NKG2D ligands was correlated with cytokine release, but was highly variable between patients. Stimulation of vascular intestinal endothelial cells in vitro induced expression of NKG2D ligands, including MICA/B and ULBP2/6. Blockade of NKG2D on CD8+ T cells inhibited the migration over ligand-expressing endothelial cells. Intestinal induction of NKG2D ligands and ligand-induced down-regulation of NKG2D in CD suggest that the NKG2D-ligand interaction may be involved in both the activation and recruitment of NKG2D+ lymphocytes into the inflamed CD intestine.

An Antibody Against Triggering Receptor Expressed on Myeloid Cells 1 (TREM-1) Dampens Proinflammatory Cytokine Secretion by Lamina Propria Cells from Patients with IBD.

BACKGROUND: Triggering receptor expressed on myeloid cells 1 (TREM-1) is a potent amplifier of inflammation. Recently, the antimicrobial peptide PGLYRP-1 was shown to be the ligand of TREM-1. Here, the ability of an anti-TREM-1 antibody to dampen the release of proinflammatory cytokines by colon lamina propria cells (LPCs) from patients with IBD was investigated and correlated with PGLYRP-1 levels. METHODS: Biopsies from patients with ulcerative colitis (UC, n = 45) or Crohn's disease (CD, n = 26) were compared with those from individuals undergoing colonoscopy for other reasons (n = 17). TREM-1 expression was analyzed on myeloid cells by flow cytometry. Cell culture experiments with LPCs were used to analyze PGLYRP-1 and inflammatory cytokine levels and assess the effect of anti-TREM-1 on cytokine secretion. RESULTS: The frequency of TREM-1-expressing neutrophils and recruited macrophages was higher in inflamed than in noninflamed biopsies. The PGLYRP-1 level in inflamed tissue was higher than in noninflamed tissue; it was produced primarily by neutrophils, and its level correlated with the secretion of proinflammatory cytokines. Secretion of myeloperoxidase, tumor necrosis factor-α, interleukin-1ß, and interleukin-8 by LPCs stimulated with the potent TREM-1 agonist consisting of PGLYRP-1 complexed with peptidoglycan was reduced in the presence of anti-TREM-1. Moreover, a blocking effect of anti-TREM-1 was apparent when LPCs from a subset of inflamed individuals with elevated PGLYRP-1 were stimulated with killed bacteria. CONCLUSIONS: An anti-TREM-1 antibody can dampen secretion of proinflammatory cytokines in inflamed patients with elevated PGLYRP-1. Moreover, PGLYRP-1 + myeloperoxidase is a potential biomarker for predicting the effect of anti-TREM-1 therapy.

Validation and Optimization of an Ex Vivo Assay of Intestinal Mucosal Biopsies in Crohn's Disease: Reflects Inflammation and Drug Effects.

Crohn's disease (CD) is a chronic illness demanding better therapeutics. The marketed biologics only benefit some patients or elicit diminishing effect over time. To complement the known methods in drug development and to obtain patient specific drug responses, we optimized and validated a known human explant method to test drug candidates and pathophysiological conditions in CD intestinal biopsies. Mucosal biopsies from 27 CD patients and 6 healthy individuals were collected to validate an explant assay test where the polarized tissue was cultured on a novel metal mesh disk, slightly immersed in medium imitating an air-liquid interphase. After culture in high oxygen for 24 hours with or without biological treatment in the medium, biopsy integrity and penetration of antibodies was measured by immunohistochemistry (IHC). Nine cytokines were quantified in the conditioned medium as a read-out for degree of inflammation in individual biopsies and used to evaluate treatment efficacy. The biopsies were well-preserved, showing few structural changes. IHC revealed tissue penetration of antibodies demonstrating ability to test therapeutic antibodies. The cytokine release to the medium showed that the assay can distinguish between inflammation states and then validate the known effect of two treatment biologics confirmed by a detection panel of five specific cytokines. Our data also suggest that the assay would be able to indicate which patients are responders to anti-TNF-α therapeutics, and which are non-responders. This study demonstrates this version of an ex vivo culture as a valid and robust assay to assess inflammation in mucosal biopsies and test of the efficacy of novel drug candidates and current treatments on individual patients-potentially for a personalized medicine approach.

Induction of lectin-like transcript 1 (LLT1) protein cell surface expression by pathogens and interferon-γ contributes to modulate immune responses.

CD161 is a C-type lectin-like receptor expressed on human natural killer (NK) cells and subsets of T cells. CD161 has been described as an inhibitory receptor that regulates NK cell-mediated cytotoxicity and IFN-γ production. Its role on T cells has remained unclear. Studies have shown that triggering of CD161 enhances NK T cell proliferation and T cell-IFN-γ production while inhibiting TNF-α production by CD8(+) T cells. Lectin-like transcript 1 (LLT1), the ligand of CD161, was found to be expressed on Toll-like receptor (TLR)-activated plasmacytoid and monocyte-derived dendritic cells (DC) and on activated B cells. Using newly developed anti-LLT1 mAbs, we show that LLT1 is not expressed on the surface of circulating B and T lymphocytes, NK cells, monocytes, and dendritic cells but that LLT1 is up-regulated upon activation. Not only TLR-stimulated dendritic cells and B cells but also T cell receptor-activated T cells and activated NK cells up-regulate LLT1. Interestingly, IFN-γ increases LLT1 expression level on antigen-presenting cells. LLT1 is also induced on B cells upon viral infection such as Epstein-Barr virus or HIV infection and in inflamed tonsils. Finally, expression of LLT1 on B cells inhibits NK cell function but costimulates T cell proliferation or IFN-γ production, and coengagement of CD161 with CD3 increases IL-17 secretion. Altogether, our results point toward a role for LLT1/CD161 in modulating immune responses to pathogens.

MUC1-derived glycopeptide libraries with improved MHC anchors are strong antigens and prime mouse T cells for proliferative responses to lysates of human breast cancer tissue.

Multi-component glycopeptide libraries and single glycopeptides were used for immunization of mice with the aim of inducing strong T helper cell responses to the repetitive sequence of MUC1 expressed by human tumor cells. The glycopeptides and glycopeptide libraries were modeled upon the native human MUC1 amino acid variable number of tandem repeats sequence by introduction of modifications in the MHC anchor positions to optimally fulfil the binding requirements of the A(d) MHC class II molecule in the BALB/c mouse. The immunogenicity of the MUC1 glycopeptides in BALB/c mice was determined by immunization in complete Freund's adjuvant and assaying lymph node T cells for a proliferative response to the glycopeptide used. Strong proliferative responses with stimulation indices over 50 were obtained with anchor-improved glycopeptide libraries as well as with single glycopeptides. Immunization with one of the glycopeptide libraries primed T cells for a proliferative cross-response to the native MUC1 glycopeptide, which by itself was nonimmunogenic. In addition, immunization with the same glycopeptide library primed T cells for a strong response to lysate of a MUC1-expressing human breast cancer, and immunization with the tumor lysate primed T cells for a response to the glycopeptide library. The T cells responding in the assay for proliferation were restricted to the A(d) MHC class II molecule. The results indicate that immunization with MHC anchor-improved MUC1 glycopeptide libraries can effectively prime T helper cells and may induce long-term memory. The approach may be useful in the design of preventive cancer vaccines for use in humans.

Low expression of insulin in the thymus of non-obese diabetic mice.

Insulin is a predominant autoantigen in IDDM in man and the NOD mouse. Failure of negative selection of diabetogenic T cells in thymus may be an important pre-disposing cause of the disease. To obtain insight into negative selection against such T-cell clones the thymic expression of insulin was studied in NOD and Balb/c mice by quantitative competitive RT-PCR. We detected RNA for insulin in the thymus of 3-week-old Balb/c mice as well as in NOD mice. However, the NOD mice expressed only half as many insulin transcripts as the Balb/c mice. Also, insulin protein was detected in the thymic medulla of both Balb/c and NOD mice. Furthermore, thymic RNA preparations were investigated for the presence of insulin transcription factors. None of the known pancreatic transcription factors for insulin; Pdx-1, Pax6 or Nkx6.1 were detectable in the thymus of Balb/c mice. These results support the idea that low insulin expression in the thymus may be a predisposing cause for development of diabetes in NOD mice analogous with what has been found in humans with the disease-disposing IDDM2 allele. Furthermore, our results suggest that insulin expression in the thymus may be regulated by different principles from those in the pancreas.

Characterization of T cell hybridomas raised against a glycopeptide containing the tumor-associated T antigen, (betaGal (1-3) alphaGalNAc-O/Ser).

T cell hybridomas were raised against the glycopeptide S(72) (Core-1) containing the tumor-associated disaccharide betaGal (1-3) alphaGalNAc (Core-1) O-linked to serine at position 72 in the mouse hemoglobin derived decapeptide Hb (67-76). All hybridomas recognized the glycopeptide S(72) (Core-1). Two of the selected hybridomas responded, however, much better to the S(72) (Tn) glycopeptide containing the monosaccharide alphaGalNAc O-linked to serine. In addition, one hybridoma cross-responded to the glycopeptide T(72) (Core-1) having a threonine at position 72 instead of a serine. No cross-responses were found to other glycopeptides consisting of the same hemoglobin peptide with different glycans attached or to the unglycosylated peptides. The T cell receptor Valpha and Vbeta usage was clearly diverse. The CDR3alpha regions demonstrated moreover a predominance of small polar amino acid side chains, and three hybridomas contained a common sequence motif. All the sequenced CDR3beta regions contained furthermore a conserved proline-glycine motif. In conclusion, immunization with the disaccharide containing glycopeptides S(72) (Core-1) created a heterogeneous population of glycopeptide specific T cells with the ability of cross-responding toward related glycopeptides.