FIG. 4.

Downregulation of MHC class I expression is an early-lytic-cycle event. (A) Surface expression of MHC class I molecules on BZLF1⁺ and VCA⁺ cells in the lytic cycle. Ag876 BL cells were simultaneously stained to detect surface MHC class I expression and intracellular lytic-cycle antigen expression exactly as for Fig. 1. The left-hand flow cytometry dot plot shows staining with MAbs W6/32 (anti-MHC class I; RPE conjugated) (y axis) and BZ.1 (anti-BZLF1; FITC conjugated) (x axis). The right-hand dot plot shows parallel staining of cells with MAb W6/32 (y axis) and L2 (anti-VCA; FITC conjugated) (x axis). (B) Surface expression of MHC class I molecules on acyclovir-treated and untreated Ag876 BL cells. Cells cultured in acyclovir for 2 weeks and replicate untreated cells were simultaneously stained with MAbs W6/32 and BZ.1 exactly as for Fig. 1. Results shown are dot plot flow cytometry profiles of W6/32 staining (RPE conjugated) (y axis) versus BZ.1 staining (FITC conjugated) (x axis) obtained for untreated control cells (left panel) and acyclovir-treated cells (right panel).