Scatter plots showing the production of CD107a (first row), IL-2 (second row), IFNγ (third row) and TNFα (last row) by VP1- (open symbols) and LTAG-specific (closed symbols) CD8+ T cell populations detected after stimulation in vitro in healthy individuals, NR patients before—and one year after transplantation, and in the Rlow, Rhigh and BKVN RTRs during follow-up.