genomewide characterization of host-pathogen interactions by ...
genomewide characterization of host-pathogen interactions by ...
genomewide characterization of host-pathogen interactions by ...
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Maren Depke<br />
Discussion and Conclusions<br />
GENE EXPRESSION PATTERN OF BONE-MARROW DERIVED<br />
MACROPHAGES AFTER INTERFERON-GAMMA TREATMENT<br />
The phagocytes <strong>of</strong> the innate immune system, neutrophils, monocytes/macrophages and<br />
dendritic cells, accomplish central functions during the encounter <strong>of</strong> <strong>host</strong> and <strong>pathogen</strong>. They are<br />
the first group <strong>of</strong> immune cells which recognize and react to an infection and the main effectors<br />
<strong>of</strong> clearance <strong>of</strong> <strong>pathogen</strong>s. Beside the different location in the non-reactive situation, when<br />
neutrophils and monocytes circulate in the blood stream and macrophages and dendritic cells are<br />
found in the tissue, macrophages and dendritic cells are long-living in comparison to the shortliving<br />
neutrophils. Macrophages and dendritic cells have important functions in the regulation <strong>of</strong><br />
the immune reaction, e. g. <strong>by</strong> their antigen presentation ability (Gordon S 2007). The central<br />
position <strong>of</strong> macrophages in the immune defense accounts for the relevance <strong>of</strong> research on<br />
macrophage related topics.<br />
Accordingly, the study described in this thesis aimed to analyze on a molecular level the<br />
reaction <strong>of</strong> macrophages to interferon-γ (IFN-γ), which in low doses is known to be a priming<br />
signal for macrophages and prepares the cells for a faster reaction to a second stimulus (Dalton<br />
et al. 1993, Huang et al. 1993, Ma J et al. 2003, Mosser 2003). Here, <strong>by</strong> utilization <strong>of</strong> bonemarrow<br />
derived macrophages (BMM), which were differentiated in vitro from bone marrow stem<br />
cells under the influence <strong>of</strong> granulocyte-macrophage colony stimulating factor (GM-CSF), any<br />
influence <strong>of</strong> immunological conditioning or in vivo stimuli were avoided. Such influences could<br />
impair the experimental results when using mature macrophages prepared from animal organs.<br />
Furthermore, recently established serum-free culture conditions (Eske et al. 2009) were applied.<br />
This new system circumvented uncontrollable influences on BMM experiments, which would<br />
have been introduced <strong>by</strong> vendor- and batch-varying, cytokine-, hormone- or endotoxincontaining<br />
serum if traditional cultivation conditions had been applied.<br />
The study included BMM <strong>of</strong> the two mouse strains BALB/c and C57BL/6, which were chosen<br />
because <strong>of</strong> the differences observed between these mouse strains in in vivo and in vitro infection<br />
studies (Breitbach et al. 2006, Autenrieth et al. 1994, van Erp et al. 2006). Thus, the data set from<br />
this study was used to compare on the one hand non-stimulated control BMM <strong>of</strong> both strains,<br />
and on the other hand BMM <strong>of</strong> the two strains after IFN-γ treatment.<br />
Another feature <strong>of</strong> this study was the combined approach <strong>of</strong> transcriptome (Maren Depke)<br />
and proteome (Dinh Hoang Dang Khoa) analysis. In the comparison <strong>of</strong> transcriptome and<br />
proteome results, it was expected that the microarray as whole genome array covered a much<br />
higher number <strong>of</strong> genes than the number <strong>of</strong> proteins covered <strong>by</strong> the gel-free LC-MS/MS<br />
proteome approach, which was already chosen as best comparable method. Anyway, a defined<br />
part <strong>of</strong> the microarray results like information on genes encoding membrane or secreted proteins<br />
can practically not match proteome results for lack <strong>of</strong> accessibility. Hence, it was not surprising to<br />
find a high number <strong>of</strong> differentially expressed genes, for which protein data were not available.<br />
Vice versa, corresponding gene expression values were recorded for almost all protein data.<br />
A good agreement <strong>of</strong> the results from both analysis levels was evident for the IFN-γ effects.<br />
Depending on the selected comparison, the overlap <strong>of</strong> differentially expressed genes and<br />
182