NK cells induce maturation or killing of autologous DCs. (A) Percent of CD86⁺ DCs (left) or mean fluorescence intensity (MFI) of MHC class II expression (right) after 24 hours of culture with 1 μg/mL LPS or 1 μg/mL HMGB1 or coculture with rNK or aNK cells at an NK/DC ratio of 5:1 or 10:1. Note that the increase in the percentage of CD86⁺ DCs varies from individual to individual, and requires a higher NK/DC ratio when rNK rather than aNK are used. (B-D) The aNK cells derived from 3 healthy donors were analyzed in a 4-hour ⁵¹Cr-release assay for their cytolytic activity against autologous iDCs (B), DCs treated 24 hours with 1 μg/mL LPS (C), or 1 μg/mL HMGB1 (D) at different NK/DC (effector-target [E/T]) ratios, from 10:1 to 2:1.