Download or read book Immune Regulation in Response to Mycobacterial Infection written by Ka-Wa Benny Cheung and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Immune Regulation in Response to Mycobacterial Infection" by Ka-wa, Benny, Cheung, 張嘉華, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled Immune Regulation in Response to Mycobacterial Infection submitted by Cheung Ka Wa, Benny for the degree of Doctor of Philosophy at The University of Hong Kong in August 2007 Mycobacterium tuberculosis (MTB) is a major cause of morbidity and mortality in the world. To combat against this pathogen, immune cells release cytokines including tumor necrosis factor (TNF)-α, which plays a pivotal role in the development of protective granulomas consisting of macrophages and other immune cells to contain the mycobacteria. Our previous results showed that Bacillus Calmette Guerin (BCG), a mycobacterial model used to investigate the immune response against MTB, stimulates the induction of TNF-α via mitogen-activated protein kinase (MAPK) in human blood monocytes. Since MAPK is regulated by MAPK phosphatase-1 (MKP-1) in response to lipopolysaccharide (LPS), the involvement of MKP-1 in BCG-induced MAPK activation and its consequent cytokine expression was examined. Primary human blood monocytes were treated with BCG and assayed for MKP-1 expression by quantitative RT-PCR and Western analysis. Here, the results demonstrated that following exposure to BCG, there was an increase in the expression of MKP-1. Additionally, there was a significant abrogation of BCG-induced MKP-1 expression in the presence of the p38 MAPK and extracellular signal-regulated kinase 1 and 2 (ERK1/2) inhibitors. The results suggested that the induction of MKP-1 was regulated by p38 MAPK and ERK1/2 in response to BCG activation. Next, the roles of MKP-1 in BCG-induced MAPK activation and TNF-α expression were elucidated with the use of MKP-1 siRNA for gene-specific knock-down. Surprisingly, when MKP-1 was blocked by MKP-1 siRNA, there was a significant decrease in the levels of phospho-MAPK and TNF-α inducible by BCG. Since TNF-α is pivotal in granuloma formation, the results indicated an unexpected positive function of MKP-1 against mycobacterial infection as opposed to its usual phosphatase function. Human Immunodeficiency Virus-1 (HIV-1) is the causative agent of acquired immunodeficiency syndrome (AIDS). Meanwhile, MTB is a leading opportunistic infectious pathogen in HIV-infected patients, and thus I postulate that HIV may play a role in regulating cytokine production in response to mycobacteria. In light of the significant roles of HIV-1 transactivator protein (Tat) in HIV replication as well as cellular cytokine dysregulation, I examined the effects of Tat on BCG-induced signaling pathways. Gene microarray profiling was used to examine global gene expressions in human blood monocytes following BCG stimulation. The results demonstrated that BCG altered multiple functions of human monocytes. The results have also shown that Tat proteins modified the genes induced by BCG; in particular, Tat affected the expression of BCG-upregulated cytokine and chemokine genes. Further evidence was provided to confirm the results of oligonucleotide microarray data by performing QPCR and ELISA assays. Suppression of IκB-α degradation by Tat resulted in abrogation of the BCG-induced TNF-α expression at both mRNA and protein levels. These observations lead to the conclusion that HIV and TB are actually interactive partners in hijacking the immune systems for their own purposes. Taken together, mycobacterial infection plays a critical role in the regulation of