<i>Staphylococcus aureus</i> is a versatile opportunistic pathogen causing a wide spectrum of diseases in both humans and animals. My research focused on characterization of the immune responses of monocyte derived dendritic cells (DC) to <i>S. aureus</i>. We initially evaluated the potential of circulating monocytes to serve as precursors for DC during <i>S. aureus</i> infection. The CD14⁺ monocytes, when stimulated with irradiated (ISA) or live <i>S. aureus</i> (LSA), differentiated into CD11c<sup>high</sup> CD11b<sup>high</sup> DC (MonoDC) in an autocrine fashion. This was associated with the up- regulation of granulocyte-macrophage colony stimulating factor (GMCSF) and tumor necrosis factor-α (TNF-α) gene transcription. We continued our studies to identify the role of TNF-α in the LSA induced differentiation of monocyte to MonoDC. Blocking TNF-α reduced the expression of CD11c and increased the expression of CD14 on LSA stimulated monocyte derived MonoDC. Stimulated monocytes were able to secrete monocyte chemotactic protein-1 (MCP-1), a chemokine that recruits monocytes to the site of infection/injury and induces the expression of β₂ integrins on DC. Characterization of the response of DC derived from monocytes using GMCSF and IL-4 revealed that, intact <i>S. aureus</i> rather than its purified structural components were efficient in DC activation. In response to ISA or LSA stimulation, DC induced proliferation of T cells collected from the peripheral circulation of cows with a history of <i>S. aureus</i> mastitis. Subsequent characterization of the proliferating T cells identified the presence of memory T cells. Finally, we identified a unique population of DEC205⁺CD8<sup>a+</sup> in monocyte derived DC. We further elucidated the role of DC DEC205, a C-type lectin, in <i>S. aureus</i> uptake. Blocking of receptor mediated endocytosis resulted in reduced uptake of <i>S. aureus</i> by DC. Confocal microscopy confirmed a role for DEC205 in <i>S. aureus</i> internalization and delivery to endosomes. DEC205 DC upon stimulation with <i>S. aureus</i> displayed enhanced maturation and antigen presentation. In conclusion, monocyte derived DC can uptake <i>S. aureus</i> and elicit cell mediated immune responses. / Ph. D.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/73012 |
| Date | 03 December 2010 |
| Creators | Bharathan, Mini |
| Contributors | Dairy Science, Mullarky, Isis K., Akers, Robert Michael, Dalloul, Rami A., Sriranganathan, Nammalwar |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation, Text |
| Format | application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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