BOTH A PRECURSOR AND A MATURE POPULATION OF DENDRITIC CELLS CAN BIND HIV - HOWEVER, ONLY THE MATURE POPULATION THAT EXPRESSES CD80 CAN PASSINFECTION TO UNSTIMULATED CD4(-CELLS() T)

Dendritic cells (DC) are the principle APC involved in primary immune responses; their major functions to obtain Ag in tissues, migrate to l ymphoid organs, and activate T cells. DC are also the first immune cel ls to arrive at sites of inflammation on mucous membranes, the major s ite of sexual transmission of HIV. We have demonstrated previously tha t three populations of cells that can develop a dendritic morphology a re present in peripheral blood. Two of these populations can express C D83, a marker of DC, and appear to be at different stages of maturatio n: 1) a precursor population and 2) a mature immunostimulatory DC. Pre cursor-derived DC express high levels of CD86 (B7-2) and HLA-DR but no CD80 (B7-1), whereas mature DC have high levels of expression of all three markers. Mature DC in peripheral blood bind HIV to their surface and induce infection when added to autologous CD4(+) T cells in the a bsence of added stimuli, such as mitogens. These mature DC, when isola ted directly from peripheral blood, appear to be conjugated to T cells , and these conjugates are infected easily and productively with HIV. These findings suggest a role for DC in early HIV infection in which t hey bind virus and interact with T cells locally or after migrating to a lymphoid organ, thus establishing a productive infection. Furthermo re, they likely play a role in the propagation of HIV infection by act ivating T cells in the presence of HIV, which leads to viral replicati on and immune cell destruction.