The presence of the vFcγRs on the surface of infected cells inhibits antibody dependent NK cell degranulation.

<p>(<b>A</b>) MRC-5 fibroblasts were infected with HSV-1F wt, ΔgE and ΔgE revertant for 24 h before cells were opsonized with HSV IgG positive and negative human sera. After 30 min of incubation, unbound antibodies were washed away and NK cells at an E∶T ratio of 10∶1 were added. After 4 h, CD107a surface expression on the NK cells was measured in FACS. Percentage of IgG-specific degranulation CD107a-positive cells = (% of CD107a-positive cells with the immune antibody opsonization - % of CD107a-positive cells with non-immune antibody). (<b>B</b>) MRC-5 fibroblasts were infected with HCMV HB5 wt, HB5Δgp68, HB5ΔIRLΔgp34 and HB5ΔIRLΔgp68/Δgp34 for 72 h before cells were opsonized with HCMV IgG positive and negative human sera. After 30 min of incubation, unbound antibodies were washed away and NK cells at an E∶T ratio of 10∶1 were added. After 4 h, CD107a surface expression on the NK cells was measured in FACS. Percentage of IgG-specific degranulation CD107a-positive cells = (% of CD107a-positive cells with the immune antibody opsonization - % of CD107a-positive cells with non-immune antibody) (<b>C</b>) MRC-5 fibroblasts were infected with HCMV HB5 wt and HB5ΔIRLΔgp68/Δgp34 for 72 h before opsonized with Cytotect or human HCMV-IgG negative sera at 1∶10 and 1∶100 dilutions. After 30 min of incubation, unbound antibodies were washed away and NK cells from six different donors at an E∶T ratio of 10∶1 were added. After 4 h, CD107a surface expression on the NK cells against HCMV-infected cells was measured. Percentage of IgG-specific degranulation CD107a-positive cells = (% of CD107a positive cells with the immune antibody opsonization - % of CD107a positive cells with non-immune antibody). Single measurements of CD107a cells are shown. One of three (A, B) or two (C) representative experiments is shown.