Neutrophils cross-prime naive CD8⁺ T cells in vitro. (A) BMNs, PENs, and DCs were pulsed with or without the indicated concentrations of Ova. After 2 hours (BMNs, ■), 4 hours (PENs, □), or 8 hours (DCs, ▧), cells were washed and cultured with highly purified naive OT1 CD8⁺ T cells at a stimulator-responder cell ratio of 2:1. After 24 hours, IL-2 was quantified in the supernatants by ELISA. Results are expressed in pg/mL as mean (± SD) of 3 separate experiments. Mann-Whitney test was performed. The data were statistically significant for DCs and PMNs (*P < .03) when compared with controls. (B) Analysis by FACS of CD80 expression by BMNs and PENs using FITC-labeled anti-CD80 mAb (white histograms); gray histograms correspond to isotype control mAbs.