M.Sc Thesis

M.Sc StudentGershoni Noga
SubjectTight Junction Proteins in Immune Cells: Regulatory
Mechanisms and Functional Significance
DepartmentDepartment of Medicine
Supervisors PROF. Ariel Miller
DR. Tamar Paperna
Full Thesis textFull thesis text - English Version


Autoimmune diseases such as Multiple Sclerosis (MS) are characterized by enhanced leukocyte migration through the blood vessel wall. Of this multi-step process, the final step, transmigration, in which the leukocyte crosses the endothelial cell (EC) layer, is the least characterized.The microvascular ECs which comprise the blood-brain barrier (BBB) are characterized by tight junctions (TJs) that provide a critical barrier to maintain brain homeostasis. The TJ protein complex includes cytosolic proteins and transmembrane proteins such as claudins. The selectivity and permeability of an endothelial or epithelial layer are determined by the unique combination of claudins expressed in a tissue-specific manner.Research conducted at our lab has detected the enhanced expression of claudin-5 in peripheral blood leukocytes of MS patients during relapse, as compared to leukocytes of MS patients during remission or of healthy controls. In the present study, our aims were to assess whether leukocyte claudin-5 plays a functional role in the enhanced migratory capacity of leukocytes of patients with MS, and to examine whether TJ genes are regulated by inflammatory conditions. In order to investigate the former, we developed an antibody targeted at claudin-5's extracellular domain, to interfere with claudin extracellular interactions, and assessed the contribution of claudin over-expression in T cells to their migration ability. To study the latter, we exposed T cells to pro-inflammatory cytokines and assessed changes in gene expression by use of quantitative PCR.Our results show that the antibodies we created affected T cell migration through endothelial layers differentially, suggesting an effect on claudin interactions both between adjacent ECs and between ECs and leukocytes. Additionally, the differential effects can point to various roles for the different epitopes against which they were created. Elevated levels of claudin expression also altered T cell migration. Analysis of the effect of the pro-inflammatory cytokines interferon-γ and TNF-α on TJ gene expression revealed an effect on several TJ genes. Our study supports a functional role for leukocyte TJ proteins in transmigration, and suggests that pro-inflammatory conditions can affect migration by altering TJ proteins expression in the leukocyte. However, further studies are required to decipher the manner in which the immune cell TJP contributes to the transmigration process, which may allow development of strategies to modulate or interfere with the process. These strategies are expected to contribute to development of therapeutics for various CNS diseases.