Increased cytotoxic degranulation of the CD56^dim NKG2A⁺ KIR⁻ NK subset against EBV-infected B cells with lytic replication. (A) PBMCs from 6 healthy EBV-positive donors were cocultured with autologous LCLs and (B) EBV-negative L428 at an effector to target ratio of 10:1 for 6 hours. Frequencies of degranulating (CD107a⁺) cells within the CD56^bright (Bright), the CD56^dim NKG2A⁺ KIR⁻ (Dim N+/K−), and the CD56^dim NKG2A⁻ KIR⁺ (Dim N−/K+) NK-cell subsets were assessed by flow cytometry at the end of the coculture. (C) HLA class I and HLA-E expression on CD19⁺ B cells from PBMCs (light gray histogram) and from autologous LCLs (dark gray histogram). Isotype controls are depicted as a white histogram. (D) Representative example of frequencies of CD107a⁺ NK cells within the 3 NK-cell subsets after coculture with latent AKBM or lytic AKBM. Frequencies of degranulating (CD107a⁺) NK cells within the CD56^bright (Bright), the CD56^dim NKG2A⁺ KIR⁻ (Dim N+/K−) and the CD56^dim NKG2A⁻ matched KIR⁺ (Dim N−/K+) NK-cell subsets in PBMCs from 3 convalescent IM patients (open symbols) and 3 healthy EBV-positive donors (filled symbols) cocultured with (E) latent AKBM or (F) lytic AKBM (n = 6). Horizontal lines indicate median values of a given subset, Wilcoxon matched-pairs signed ranks tests.