genomewide characterization of host-pathogen interactions by ...

Maren Depke
Introduction
phenotype of macrophages changes from production of IL-12 to IL-10 production, whereas TNFα,
IL-1, and IL-6 are still secreted (Mosser 2003). Type II activation initiates a Th2-based immune
response. There is experimental evidence that the phenotype of macrophages is primarily
determined by the first cytokine type to which they are subjected (Erwig et al. 1998).
A naïve macrophage can react to activation stimuli. Nevertheless, when the macrophage
received a priming signal in advance, it had the possibility to prepare for the potentially following
second stimulus by transcriptional regulation and is able to react stronger and faster to
activation. Low-dose IFN-γ is the most important macrophage priming signal. Primed
macrophages are not activated yet and do not secrete proinflammatory cytokines. This occurs in
classical activation after a second signal like IFN-γ or LPS, peptidoglycan, and others (Dalton et al.
1993, Huang et al. 1993, Ma J et al. 2003, Mosser 2003).
Fig. I.6: Inducers and selected functional properties of different polarized macrophage populations.
Abbreviations: DTH – delayed-type hypersensitivity; IC – immune complexes; IFN-γ – interferon-γ; iNOS – inducible nitric oxide
synthase; LPS – lipopolysaccharide; MR – mannose receptor; PTX3 – the long pentraxin PTX3; RNI – reactive nitrogen intermediates;
ROI – reactive oxygen intermediates; SLAM – signaling lymphocytic activation molecule; SRs – scavenger receptors; TLR – Toll-like
receptor.
From: Mantovani et al. 2004.
Studies aiming to analyze the reaction in general and more specific the gene expression
pattern of macrophages are impaired by the influence of immunological factors on the mature
macrophages which can be prepared from animal organs, even under highly standardized
laboratory conditions. This problem can be circumvented when using bone-marrow derived
macrophages (BMM). Bone marrow stem cells are prepared from the animal and cultivated
in vitro for proliferation and differentiation. Under the influence of granulocyte-macrophage
colony stimulating factor (GM-CSF) cells differentiate into macrophages, which have the
advantage of having never received any in vivo stimulus or immunological conditioning that
might influence their cellular reaction.
Until recently, further uncontrollable influences on macrophage or BMM experiments were
introduced by the utilization of serum-supplemented culture medium. Serum contains immune
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