398
Antigen Presenting Cells (APCs)
responses (Fig. 14). In response to viruses
and
Streptococcus pneumoniae
, DCs can ac-
tivate B cells via secretion of proinflamma-
tory type 1 interferons, thereby promoting
immunoglobulin isotype switching. Most
recently, it has been observed that there are
reciprocal activatory interactions between
NK cells and DCs. The cross talk between
both cell types appears to be relevant in
innate antitumor responses.
10.7
DCs in Immunotherapy
The superior role of DCs in triggering
antigen-speci±c T-cell responses has pro-
vided the rationale for developing new vac-
cination strategies based on the injection
of DCs loaded with antigen
in vitro
.In
most immunotherapy protocols, autolo-
gous CD34
+
precursor-derived DCs or
monocyte-derived DCs from healthy vol-
unteersorpatientsarebeingused
.
In vaccination against tumors, the ulti-
mate goal is to prime CD4
+
and CD8
+
T
cells with antitumor reactivity. To achieve
this, ef±cient and stable loading of MHC
molecules of DCs with cognate tumor
antigens is necessary. Two strategies are
employed to provide antigens: an endoge-
nous and an exogenous way. Endogenous
antigen expression was obtained by us-
ing bulk RNA prepared from tumors or
retroviral, adenoviral, or poxviral vectors
to transduce DCs with genes coding for
the respective tumor antigens. Another
Mature
DC
Extracellular
pathogens
Ig isotype switching
B cell
Intracellular
pathogens,
viruses,
yeast
NK cell
Viruses
CTL
Bordetella
pertussis
T-regulatory
cell
T
H2
T
H1
Viruses
streptococcus pneumoniae
?
Fig. 14
The plasticity of DCs. Mature DCs in the draining lymph node are capable of delivering
different signals according to the microbes they encounter in the periphery.
previous page 398 Encyclopedia of Molecular Cell Biology and Molecular Medicine read online next page 400 Encyclopedia of Molecular Cell Biology and Molecular Medicine read online Home Toggle text on/off