MECNHANISMS OF CELL ADHESION AND TRAFFICKING IN EXPERIMENTAL ILEITIS

Project 4，由Dr. Klaus Ley领导，研究SAMP1/YitFc （SAMP）小鼠肠道T细胞粘附和炎症细胞运输的机制。最初的项目旨在验证以下假设：1)SAMP小鼠表达与T细胞、中性粒细胞和其他白细胞运输相关的粘附分子；2)白细胞和/或内皮粘附分子是SAMP小鼠转移的CD4+ T细胞受体发生回肠炎所必需的；3)CD4+ T细胞使用特定的粘附分子回到SAMP小鼠的回肠末端并引起疾病。在过去的四年中，内皮粘附分子VCAM-1、ICAM-1、MAdCAM-1、p -选择素和PNAd在SAMP回肠炎症区显著上调，这一发现取得了重要进展。治疗性研究表明，阻断α 4整合素、VCAM-1和ICAM-1的联合或MAdCAM-1和l -选择素的联合可显著改善过继转移模型中的疾病严重程度。l -选择素对促进炎症很重要的发现代表了对该分子的一种新颖和意想不到的观察，因为l -选择素被认为是在幼稚T细胞上表达的。然而，抑制l -选择素可能会限制炎性髓细胞的募集，以及幼稚T细胞、记忆T细胞和调节性T细胞，或其组合。此外，我们发现B细胞在回肠炎SAMP模型中起致病作用。在下一个资助期，项目4将重点研究l -选择素及其配体之一PSGL-1，基于两个最近的发现：1)证明l -选择素的重要性

Project 4, headed by Dr. Klaus Ley, studies the mechanisms of intestinal T cell adhesion and inflammatory cell trafficking in SAMP1/YitFc (SAMP) mice. The original project was designed to test the hypothesis that: 1) SAMP mice express adhesion molecules relevant to the trafficking of T cells, neutrophils, and other leukocytes, 2) leukocytes and/or endothelial adhesion molecules are required for the development of ileitis in recipients of CD4+ T cells transferred from SAMP mice, and 3) CD4+ T cells use specific adhesion molecules to home to the terminal ileum of SAMP mice and cause disease. In the past four years, important progress has been made with respect to the discovery that the endothelial adhesion molecules VCAM-1, ICAM-1, MAdCAM-1, P-selectin, and PNAd are significantly upregulated in inflamed areas of the SAMP ileum. Therapeutic studies have shown that blocking alpha 4 integrins, a combination of VCAM-1 and ICAM-1, or a combination of MAdCAM-1 and L-selectin significantly ameliorates disease severity in the adoptive transfer model. The finding that L-selectin is important in promoting inflammation represented a novel and unexpected observation regarding this molecule, since L-selectin is thought to be expressed on naive T cells. However, L-selectin inhibition may limit the recruitment of inflammatory myeloid cells, as well as naive, memory, and regulatory T cells, or a combination thereof. In addition, we discovered that B cells play a pathogenic role in the SAMP model of ileitis. For the next funding period, Project 4 will focus on L-selectin and one of its ligands, PSGL-1, based on two recent discoveries: 1) demonstration of the importance of L-selectin in mediating ileitis, and 2) preliminary evidence that PSGL-1 is expressed in endothelial cells of lamina propria microvessels in the terminal ileum. Based on these discoveries, this project will first test whether the L-selectin ligand PSGL-1 is expressed in inflamed endothelial cells of the ileal lamina propria and submucosa using immunostaining, laser capture microdissection, and real-time RT-PCR. The functional role of the PSGL-1/L-selectin pathway of adhesion will be studied using monoclonal antibodies to block PSGL-1, as well as by crossing SAMP mice with existing PSGL-1 deficient mice using speed congenics. Finally, the nature of L-selectin expressing cells that contribute to ileitis severity in the SAMP adoptive transfer model will be studied. These studies are designed to understand the mechanisms of trafficking of pathogenic, naive and regulatory lymphocytes in the inflamed ileum of SAMP mice and to provide a rational basis for ameliorating disease severity by single or combined blockade of intestinal-specific adhesion molecules in patients with Crohn's disease.