Accumulation of activated HLA-DR⁺ CD8⁺ T cells and CD56^dim NK cells during acute IM. PBMCs from healthy controls, IM-like patients, and IM patients at acute phase (IM acute), at 1 (IM 1 month), and 6 months (IM 6 months) were analyzed by flow cytometry. Frequencies of (A) CD8⁺ T cells within the CD3⁺ T-cell population and (B) HLA-DR⁺ CD8⁺ T cells within the CD8⁺ T-cell population in healthy controls (n = 19), IM-like (n = 11), and IM acute (n = 20), 1-month (n = 10) and 6-month (n = 7) patients. (C) EBV DNA load in copies per 10⁶ PBMCs in IM-acute (n = 19), 1-month (n = 14), and 6-month (n = 9) patients. Counts (cells/µL blood) of total NK cells (D) and frequencies of CD56^bright CD16⁻, CD56^dim CD16⁻, and CD56^dim CD16⁺ NK-cell subsets within the CD3⁻ CD56⁺ NK-cell population from representative healthy control, IM-acute and 1-month patient (E). Counts (cells/µL blood) of (F) CD56^bright CD16⁻, (G) CD56^dim CD16⁻, and (H) CD56^dim CD16⁺ NK cells in healthy controls (n = 31), IM-like patients (n = 11), and IM-acute (n = 18), 1-month (n = 10), and 6-month (n = 8) patients.