Mature moDCs infected with HCMV decrease membrane expression of CD83 and release increased amounts of soluble CD83 into the supernatant. CD83 rapidly disappears from the surface of IE1-positive mature moDCs but is still expressed intracellularly on (A) day +1 or (B) day +3 after infection (shaded histograms, isotype controls; open histograms, anti-CD83). Positive controls for surface CD83 expression comprise the non-HCMV-exposed moDCs as well as the bystander, uninfected and thus IE1-negative moDCs in the HCMV-exposed cultures. (C) ELISAs detected soluble CD83 in the supernatants of infected and uninfected mature moDC cultures (n = 3; mean ± SD), each assessed in triplicate. Infected mature moDC cultures released significantly more soluble CD83 than uninfected control cultures (^*P < .05; Student t test). HCMV-infected and uninfected HUVECs, which never express CD83, provided the negative controls (left). Soluble CD83 could not be detected after CD83 immunodepletion (right).