Abstracts (complete list) - Wissenschaft Online

Svetlana Karakhanova, Karsten Mahnke, Alexander Enk
Differential modulation of B7-H1 expression in pDCs and
mDCs upon maturation of dendritic cells (DCs).
Expression of regulatory molecules of the B7-H family by DCs plays an important role in
the regulation of immune responses. However, their function(s) as well as regulation of
their expression during DC maturation is not completely understood. To test how
different types of DC maturation affect expression of these molecules, we stimulated in
vitro prepared monocyte derived DCs (MoDCs) as well as genuine DCs, isolated from
peripheral blood of healthy donors. Stimulation of MoDCs with a cytokine cocktail
resulted in increased stimulatory capacity as well as increased expression of CD80,
CD83, CD86 molecules. In parallel we observed upregulation of B7H1. Similar results
were observed using genuine DCs. This means that cytokine cocktail maturated genuine
DCs showed enhanced stimulatory capacity and upregulation of B7H1 expression. While
MoDC represent a homogenous population of myeloid origin, genuine DCs consist of a
mixed (mDC and pDCs) population with a different repertoire of TLR receptors. Total
genuine DC populations were stimulated with various TLR ligands and assessed by FACS
and functional assays to determine whether the surface expression of B7H1 molecules is
affected. LPS as well as cytokines enhance expression of B7H1 preferentially in mDC,
while Poly IC induced B7H1 expression in pDC. We furthermore show that stimulation
activates the MAPK kinase pathway in MoDCs and blocking of ERK/MAPK
phosphorylation with a specific inhibitor reduced increased B7H1 expression. This
indicates that the expression of B7H1, at least in part, is regulated by the MAPK kinase
pathway. Additional assays are going to be performed to identify supplementary
signalling events responsible for B7H1 upregulation and to dissect the initial receptor/
receptors responsible for activation.