CD4+ T lymphocytes have long been shown to be the site of HIV replication,
but monocyte/macrophages and dendritic cells, which express the CD4
receptor, were susceptible to harbor the virus as well. It was important to
quantitate their infection, because they were thought to be a reservoir of
HIV, and dendritic cells confer infection to CD4+ T lymphocytes optimally
in vitro, particularly when they activate them during antigen
presentation, but their isolation is not as straightforward as that of
lymphocytes. Quantitation of infected dendritic cells in the blood yielded
conflicting results, probably due to differences in isolation methods.
Interaction between immune cells as well as HIV replication are very active
in secondary lymphoid organs rather than in blood. Therefore we chose to
quantify infected cells from the spleen, which is a major secondary
lymphoid organ.
