What are the effects of HIV on macrophages,dendritic cells, and other cells?
Macrophages can be bound and infected with HIV. Although they express only
low levels of CD4, they express large amounts of cytokine receptors (especially of
the CCR5 family), which may compensate for low CD4 expression. In addition,
macrophages can be infected after they phagocytose dead or dying HIV-infected
cells. Usually, macrophages are not killed by the virus, but instead become a
reservoir for HIV. Much more of the virus is stored in macrophages than in T
cells; examples of tissues where macrophages are the number one ‘‘storage room’’for HIV include the brain and lungs.
HIV-infected macrophages may be impaired in antigen presentation and cytokine production. Dendritic cells can be infected by HIV and, like macrophages, are usually not killed by it; it is believed that dendriticcells play a major role in transmitting the virus to naive T cells. It has been recently demonstrated that the transmission of HIV from dendritic cells to naive T cells is greatly enhanced by triggering of the CD40 molecule expressed on dendritic cells.
Among other cells that feature prominently in HIV infection, follicular dendritic
cells deserve mention because they trap large amounts of HIV bound by antibo-
dies, through their Fc receptors. This may impair the physiologic function of
follicular dendritic cells in the selection of high-affinity antibodies in germinal
centers