Dokument 1.pdf - OPUS - Universität Würzburg

2 Summary
2 Summary
Following a stem cell or solid organ transplant immunosuppressed patients have an increased
risk of developing opportunistic infections such as invasive aspergillosis (IA), which is
mainly caused by the most prevalent airborne mold, Aspergillus fumigatus. The diagnosis and
therapy of IA have become increasingly relevant in recent years, making it essential to
understand the mechanisms of the immune system.
The infection generally spreads from the lung. Dendritic cells (DCs), whose major task is to
activate T-lymphocytes, were therefore investigated for their ability to influence the immune
system. 40-0-[2-Hydroxy-ethyl]rapamycin (RAD), a novel immunosuppressive drug, was
analysed for its in vitro influence on the interaction of neutrophils and monocyte-derived
dendritic cells (moDCs) with the pathogenic mould, A. fumigatus. RAD acts by bonding with
the cytosolic FK506 binding protein (FKBP12) causing inhibition of the lipid kinase
mammalian target of rapamycin (mTOR) which in turn results in the repression of T-cell
activation. It is clinically used to prevent graft-versus-host disease or the rejection of solid
organ and bone marrow transplants. RAD-treatment significantly decreased the oxidative
burst of neutrophils after confrontation with A. fumigatus. moDCs were derived from
monocytes through culture with granulocyte-macrophage colony-stimulating factor and
interleukin-4 in the presence or absence of 10 nM RAD. Although there was no difference in
the expression of the surface markers CD1a + , CD14 - and HLA-DR + , RAD had various
modulating effects on the immune function of moDCs. It reduced the expression of innate
immunity receptors (TLR4 and dectin-1) and impaired the maturation capacity of moDCs as
was observed in the reduction of co-stimulatory factors (CD40, CD83 and CD86). CD40
remained significantly reduced even after treatment with A. fumigatus, while CD83 only
exhibit a downstream trend and CD86 did not stay reduced. RAD treatment significantly
reduced the cytokine expression levels of IL-12, TNF-α, and CCL20 after 6 h stimulation of
the moDCs with the mold. This was to some extent confirmed at protein level, where the
same cytokines as well as IL-10 were significantly reduced in RAD-treated moDCs by
comparison with reference cells after 12 h of stimulation with A. fumigatus. The phagocytosis
and binding rate of dextran beads and conidia as well as the damage to A. fumigatus germ
tubes were significantly reduced in DCs treated with the agent. It cannot be determined for
certain whether moDCs under RAD-treatment were also less able to activate CD8 + -T-
lymphocytes because of the wide donor related discrepancies that they displayed.
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