Recombinant IL-10 and HCMV-IL-10 inhibit dendritic cell differentiation. To examine whether HCMV infection of monocytes alters the secretion of cytokines, supernatants were collected from HCMV-infected monocytes (HCMV-Mo) and dendritic cell (DC) cultures. The levels of cytokines (A) IL-1β, (B) IL-6, and (C) IL-10 in the cultures were determined at the time points indicated. Recombinant IL-6, recombinant IL-10, or HCMV-IL-10 was added to the cultures at the same time as cytokine stimulation, and antibodies against IL-10 and the IL-10 receptor (IL-10 R) were added to test if the HCMV effect could be reversed.