HCMV specifically affects the HLA-DR α-chain in infected cells. Fibroblasts were examined for the presence of HLA-DR mRNA in uninfected and HCMV-infected cells at 1 day after infection, using an RT-PCR assay. The transcription of HLA-DR in HCMV-AD169, RVAD65-infected fibroblasts, or uninfected cells is shown in panel A (n = 5). To analyze whether HCMV induces degradation of HLA-DR molecules, immunoprecipitation experiments were performed. The presence of HLA-DM or the HLA-DR α-or β-chain is shown in panel B at 1 and 2 days after infection (n = 3). The effect on newly synthesized HLA-DR α molecules was examined in cells after 4 hours of infection and 2 hours chase in mock-infected, AD169-, or RVAD65-infected cells (C). The distribution of HLA-DR and the expression of pp65 were examined by confocal microscopy. The HLA-DR expression in mock-infected cells and HCMV-infected cells at 1 day after infection is shown in panel D. The HCMV protein pp65 was present in the nucleus in HCMV-infected cells (D) at 1 day after infection. Original magnification, × 40.