CD4 T cells play an important role in the initiation and maintenance of inflammation in numerous inflammatory diseases. Rheumatoid arthritis (RA) is one such autoimmune inflammatory condition where inflammation of the joint occurs. CD4 T cells are one of the key cells in RA pathogenesis due to their ability to activate or influence other cells in the joint including B cells, macrophages and osteoclasts, which collectively lead to joint destruction. The recruitment and function of CD4 T cells at inflamed tissues has been studied extensively. However, the signals that regulate CD4 T cell accumulation and persistence at peripheral inflamed sites are poorly understood. In this study, a novel in vivo model of inflammation was designed in the murine ear pinnae to study the signals which regulate CD4 T helper 1 (Th1) cell persistence at inflamed tissues. Congenically marked, in vitro polarised CD4 Th1 cells were adoptively transferred directly into inflamed or non-inflamed ear pinnae and their persistence and survival were studied using flow cytometry. Higher numbers of CD4 Th1 cells were found at the inflamed as compared to the non-inflamed site. Intravital microscopy was used to further study the behaviour of these cells. Th1 cells were found to be more mobile in inflamed compared to non-inflamed ear pinna. To investigate the molecular mechanism of this, either the ear pinnae or the T cells themselves were manipulated. Introducing cognate antigen at the inflamed site did not alter the number of recovered T cells, nor did the T cells proliferate at the site. Next, the survival of persistent CD4 Th1 cells was examined by investigating their expression of active caspases. Lower proportion of Th1 cells recovered from inflamed tissues were found to express active caspases compared to those from a non-inflamed site. Together these data suggest that local T cell activation is not required for persistence but rather, the increase in T cells at inflamed sites may be due to a combination of persistence and survival signals. The sphingolipid sphingosine-1-phosphate (S1P) has been implicated in driving both egress of T cells out of secondary lymphoid organs and their survival. To investigate whether S1P affects Th1 cell persistence and/or survival at inflamed tissues, Th1 cells were treated with S1PR agonists or antagonists, prior to transfer. Fewer Th1 cells were recovered from the inflammatory site of mice injected with antagonist treated cells. Additionally, S1PR agonism was sufficient to induce Th1 cell persistence at non-inflamed tissues. A trend towards increased expression of active caspases was also found in S1PR antagonist treated T cells recovered from inflamed ear pinnae compared to untreated controls. Finally, elevated levels of the S1P metabolising enzyme, SPHK1, was found in human RA joints compared to OA joints. In sum, I propose a novel function for S1P and its receptors in regulating the persistence of activated CD4 Th1 cells at inflamed tissue sites. Moreover, targeting S1P and its receptors at peripheral inflamed tissues could provide a novel target for the development of more effective anti-inflammatory therapeutics.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:739281 |
| Date | January 2018 |
| Creators | Jaigirdar, Shafqat Ahrar |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/8952/ |
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