The role of interleukin 15 in three murine models of inflammation

Walker, Richard (2004) The role of interleukin 15 in three murine models of inflammation. MSc(R) thesis, University of Glasgow.

Abstract

Research into the causes and roots of inflammation has provided a vast literature from which to draw. In spite of this data, major human diseases such as rheumatoid arthritis or the effects of sepsis following injury continue to cause suffering and sometimes death. Research has led to several main contenders for the title of "protein at the top of the inflammatory cascade." but again, reading the vast knowledge that others have uncovered, it is plain to see that there are redundancies, and a legion of control mechanisms operating to join all the major cytokines and cell types that constitute the mammalian inflammatory response. Amongst one of the recently pro-inflammatory proteins is lnterleukin-15. (IL-15) IL-15 was discovered in 1994 and has since been associated with up-regulation of inflammation and postulated as a controller of tumour necrosis factor alpha. The IL-15 protein is similar in structure to the IL-2 protein in several mammalian species. However in spite of its structural homology, there is little or no sequence homology with IL-2. The experiments here are performed in the murine models of human diseases. The murine IL-15 shares approx 73% sequence homology with the human IL-15. Thus this project set out to clone what at the time, was commercially unavailable, namely murine recombinant IL-15 and to raise antibodies against this protein. It was the intention to use these antibodies as therapeutic agents in three murine models of inflammation; the Collagen Induced model, the LPS shock model of sepsis and finally the septic arthritis model. Recombinant murine IL-15 was cloned, purified and used to raise rabbit anti-muIL-15 antibodies. These anti sera were used in the CIA model. Furthermore, the cloning process uncovered a mutant form of murine IL-15 which had the native binding characteristics but had no ability to activate T cells. This protein was also used therapeutically in the CIA model as a putative therapeutic agonist to IL-15. Neither experiment produced clear indications that the anti -IL-15 anti bodies or the mutant agonist were successful in abrogating the symptoms of CIA however there was a trend for early and subtle amelioration of symptoms. The difficulties with purification of recombinant protein and particularly solubility indicated a change to the original protocol. Instead of using the recombinant IL-15 & its antibody to continue the investigation in the remaining two models, the more readily purified soluble IL-15 Receptor alpha (IL-15Ralpha) was used as the therapeutic agent. In both the LPS shock model and the septic arthritis model, the therapeutic inoculation of the mice with lL-15Ralpha, seemed to modify the mortality associated with high dose LPS shock in the LPS model; severity and incidence of sepsis in both models. There was also a trend for reduced incidence and severity of arthritis in the septic arthritis model. Furthermore, IL-15R? therapy appeared to alter the distribution of S. aureus in the soft tissues of the septic arthritis mice. In this instance, S. aureus was found in the IL-15Ralpha treated group tissues but not in the control group, suggesting IL-15 removal had some effect on the ability of the tissues examined to clear the bacteria. This finding was also either time dependant or related to the cessation of therapy as the differential distribution generally disappeared following the cessation of therapy and then resembled the controls. IL-15Ralpha administration also appeared to affect the ability of the spleen cells from mice in the septic arthritis mice also to react to the mitogens, SEA and CON-A, with the treatment mice showing less activity than the control mice during the treatment period. In the many determinations of the effects of IL-15 throughout this study, there have not been any constantly obvious and statistically significant differences, however, an overall conclusion can be drawn that there is a persistent trend for the amelioration of sepsis and arthritis in the CIA, LPS and Septic arthritis models when IL-15 depleting agents such as anti-IL-15 antibodies, IL-15 antagonist and soluble receptor are administered therapeutically. This study therefore, may provide the basis for better defined experiments to be carried out, perhaps with better power and sampling and reagents, strengthening this trend into a fact.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Additional Information: Adviser: Max Field
• Keywords: Immunology
• Date of Award: 2004
• Depositing User: Enlighten Team
• Unique ID: glathesis:2004-74201
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 23 Sep 2019 15:33
• Last Modified: 23 Sep 2019 15:33
• URI: https://theses.gla.ac.uk/id/eprint/74201