Neutrophils from lung recipients activate DCs in a contact-dependent manner. (A) IL-12 and MHC II (I-A^d) expression in Balb/c BMDCs cultured for 24 hours alone or with BAL neutrophils from Ext CI B6 → B6 lung transplantations at a BAL neutrophil to BMDC ratio of 1:1 or 3:1, or separated by a Transwell at a ratio of 3:1. (B) Percent abundance of intragraft IL-12⁺ I-A^d+ cells in Min CI or Ext CI Balb/c → B6 transplantations on POD 1. (C) IFN-γ expression after stimulation with Balb/c splenocytes in CD8⁺ T cells isolated from B6 mice 1 week after injection of immature Balb/c BMDCs (DC), BAL neutrophils (PMN) from Ext CI B6 → B6 transplantations, Balb/c BMDCs cultured with PMN, or Balb/c BMDCs cultured with PMN separated by a Transwell. (D) Percent abundance of intragraft IFN-γ⁺CD4⁺ and IFN-γ⁺CD8⁺ T cells (n ≥ 6; left), histology (n ≥ 6; center), and rejection scores (n = 5; right) in costimulation blockade-treated Min CI or Ext CI Balb/c → B6 transplantations on POD 7. Results are shown as means ± SEM. *P < .05; **P < .01. Data for panels A-E are representative of ≥ 3 independent experiments unless otherwise noted.