During heterosexual intercourse, seminal fluid containing HIV contacts vaginal squamous mucosa. Cells capture virions and transport the virus via lymphatics to regional lymph nodes. Within the germinal centers of these lymph nodes, the virions infect CD4+ lymphocytes and proliferate, causing CD4+ cell lysis with release of more virions, which are taken up on the surface of cells having Fc receptors, allowing continued infection by HIV of more CD4+ cells passing through the nodes. Which of the following types of cells is most likely to capture HIV on its surface via Fc receptors?