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11
Dendritic Cells Ferry HIV-1 From
Periphery into Lymphoid Tissues
Teunis B. H. Geijtenbeek and Yvette van Kooyk
Department of Tumor Immunology, University Medical Center St Radboud,
Nijmegen, The Netherlands
INTRODUCTION
Dendritic cells (DC) were ®rst described in 1868 by Langerhans in the skin, but
it was not until 25 years ago that their function as potent stimulators of primary
immune responses was recognized (Steinman and Cohn, 1973). Initially, prog-
ress into the characterization of DC was slow because of their low frequency,
lack of markers to distinguish them from the abundant monocytes and macro-
phages, and the problems involved in purifying them. Research into their im-
mune-regulatory function was greatly facilitated by the discovery that DC
could be grown in culture from proliferating progenitors or nonproliferating
precursors such as monocytes ( Romani et al., 1994; Sallusto and Lanzavecchia,
1994).
DC are important sentinels of the immune system and are therefore essential
for the onset of a strong immune response against incoming pathogens, such as
human immunode®ciency virus (HIV )-1. However, besides being responsible
for eliciting an HIV-1-speci®c response, it is now becoming evident that DC
also participate in the dissemination of HIV-1. Sexual transmission via any of
the oral, rectal, and vaginal mucosa is the most common route for infection
with human HIV-1 worldwide. Although the nature of the immunological re-
sponses at these sites may di¨er, dissemination of HIV-1 could be facilitated by
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