Fig. 4.

Long-term MPA incubation significantly inhibits phosphorylation of central intracellular signaling molecules in NK cells. Influence of long- and short-term MPA incubation on STAT-3, STAT-4, STAT-5, AKT and ERK1/2 phosphorylation. Intracellular signaling molecules became phosphorylated upon IL-2 stimulation with an activation peak at day 6 (STAT-3,-5, ERK1/2) or day 9 (STAT-4, AKT), (white square) compared with unstimulated NK cells at day 0. Long-term MPA incubation (red triangle) significantly inhibited the IL-2-induced phosphorylation/activation, while short-term (24 h) MPA treatment (orange triangle) had no or a minimal effect on previously activated signaling molecules (n = 10, plots gated on CD56⁺CD3⁻ NK cells, p < 0.05 and p < 0.01 indicated as * and **, Wilcoxon matched-pairs signed rank test). Overlay plots show representative results regarding p-STAT-3, -4, -5, p-AKT and p-ERK1/2 expression following 6d IL-2 stimulation (black) ± long-time (red) MPA incubation compared with unstimulated NK cells at d0 (gray) and autofluorescence (gray area), (MFI vs. events, plots gated on CD56⁺CD3⁻ NK cells)