In initial experiments, lines of transgenic parasites were generated in which the MHC II-dependent T cell epitope Moth Cytochrome C (MCC) was expressed within a number of different fusion proteins, to provide a model in which the fate of parasite-derived antigens could be followed in infected DC. MHC II-MCC complex formation in CD and MΦ complex-specific T cell line. Although the fusion proteins were clearly demonstrated to be secreted at high levels, no cell surface staining could be detected with D4 and neither infected DC nor infected MΦ could stimulate T cell proliferation. <i>Leishmania-</i>infected DC were however, shown to efficiently process and present exogenous antigen to T cells <i>in vitro.</i> Alternative strategies were therefore developed to probe the DC:<i>Leishmania</i> interaction in more detail. Investigation into the effect of uptake of EGFP-expressing <i>L. mexicana </i>parasites by different DC cultures <i>in vitro</i> demonstrated that, in the absence of exogenous factors, uptake of <i>L. mexicana </i>amastigotes did not cause activation of DC. Uptake of <i>L. mexicana </i>promastigotes resulted in activation of a small proportion of DC indicating that promastigotes do encode an activation signal, but that this is not sufficient to activate the entire DC population. However, neither <i>L. major </i>promastigotes nor <i>L. mexicana </i>promastigote mutants lacking surface lipophosphoglycan (LPG) activated DC <i>in vitro. </i>Therefore these data suggest that <i>L. mexicana </i>promastigotes encode an activation signal, but that this is not sufficient to stimulate all DC. As the promastigotes which did not activate DC either lacked, or expressed a modified version of, LPG, we propose that LPG is a <i>L. mexicana </i>pathogen-associated molecular pattern (PAMP). The work presented in this thesis demonstrates that infected DC are capable of initiating that anti-<i>Leishmania </i>response <i>in vivo, </i>as they efficiently present antigen to T cells. However, infection <i>per se </i>is not sufficient to activate all DC. These data therefore suggest that during the initiation of an anti-<i>Leishmania </i>T cell response DC are likely to be activated by factors produced in response to injection of parasites by the insect vector, such as pro-inflammatory cytokines.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:641530 |
| Date | January 2002 |
| Creators | Bennett, Clare Louise |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14006 |
Page generated in 0.0118 seconds