Robert-von-Ostertag-Str. 7-13
14163 Berlin
+49 30 838 51833
virologie@vetmed.fu-berlin.de
DC can be isolated from skin as epidermal Langerhans cells, from various tissues or
generated from monocytes (MoDC). For differentiating MoDC and for in vitro culture of
DC, eq.GM-CSF and eq.IL-4 are necessary cytokines. Both cytokines are considered
species-specific. Using degenerated primers delineated from other species, cDNA of the
ORFs coding for eq.GM-CSF and eq.IL-4 were cloned. The coding region of the cytokine
was cloned in various expression systems. For eq.GM-CSF RACE cloning for the 3’
terminus was performed also. For differentiating MoDC, monocytes were stimulated with
the equine Cytokines. MoDC were analysed by light- and electronmicroscopy, flow
cytometry and MLR.
RACE and revealed that eq.GM-CSF is distinctly related to hu.GM-CSF with an amino
acid homology of just 77 %, whereas other species have homologies to each other of more
than 90 %. Additionally, a point deletion at the 3’ end of the ORF, resulted in a 24
nucleotides extended ORF not described in any species thus far. Computer analysis of the
resulting protein indicates an altered N-terminus of the protein, as the human signal peptide
cleavage site was not conserved either. Cloning of eq.IL-4 revealed a new sequence
distantly related to other species. Strikingly and in contrast to previous reports in other
species, human and equine GM-CSF were cross-reactive and could be used to stimulate
equine MoDC, although a much higher concentration of hu.GM-CSF was required (20-
fold). IL-4 in contrast was strictly species specific indeed. Using eq.GM-CSF or hu.GMCSF
plus eq.IL-4, MoDC were generated with the typical morphology and function of DC,
including the ability to stimulate allogeneic T cells in a MLR. In contrast to the human
system, however, monocytes had to be differentiated for 5-6 days before MoDC were
obtained from horses.