Neutrophils induce ovalbumin-specific CD8⁺ T-cell proliferation ex vivo and in vivo. (A) Neutrophils present Ova as MHC I–bound peptides in vivo. PENs purified from mice 6 hours after a peritoneal injection of 200 μg Ova or PBS were used to stimulate OT1 CD8⁺ T cells. After 24 hours, IL-2 was quantified in the supernatants by ELISA. Results are expressed in pg/mL as mean ± SD of 3 independent experiments. Mann-Whitney test was performed. The data were statistically significant for PMNs (*P < .03) when compared with PBS. (B-D) Ova-pulsed neutrophils induce naive CD8⁺ T-cell proliferation in lymph nodes and spleen (C). β2-Microglobulin^−/− mice were injected with CFDA-SE naive OT1 CD8⁺ T cells followed 1 day later by injection of Ova or Ova-pulsed LB27.4, Ova-pulsed DCs, or Ova-pulsed BMNs. Four days later, lymphocytes were isolated from spleen and lymph nodes and CD8⁺ T-cell proliferation was analyzed. Data are representative of 1 of 3 separate experiments. (D) Data are presented as the mean percentage of OT1 CD8⁺ T cells in each cycle (mean ± SD of 3 independent experiments). ANOVA test was performed. The data were statistically significant for DCs and PMNs (*P < .001) when compared with controls.