a Control mice (nLung), or mice carrying early (e) or late (l) KP tumors were challenged i.t. with CTV labeled apoptotic thymocytes. Two hours later total lung cell suspensions were analyzed by flow-cytometry to assess the fraction of phagocytes associated to fluorescence. Representative flow cytometry plots of cDC1 (gated on CD45+/Cd11c+/SiglechF−/MHC-IIhigh/CD11b−) and quantification of uptake, expressed as percentage of CTV+ cDC1. Data were examined over two independent experiments: nLung n = 8, KP(e) n = 5, KP(l) n = 5, one-way ANOVA followed by Tukey’s post-test. b Mice were challenged with KP-BFP cells. Lungs were harvested at early or late time points after challenge to prepare total lung cell suspensions. Representative flow cytometry plots displaying the percentage of BFP+ cDC1 and the corresponding quantification. Data are pooled from two experiments with n = 8 mice per group, two-tailed unpaired t-test. c, d Sorted-cDC1 cells from nLung, early or late whole tumor tissues were incubated for 30’ (binding, c) or 2 h (uptake, d) with CFSE labeled apoptotic thymocytes. c Representative micrographs showing cDC1 binding to thymocytes. The percentage of cDC1 in contact with at least one thymocyte was quantified on 30 individual cells acquired on separated fields in two independent experiments. d Representative micrographs showing thymocytes uptake. The percentage of cDC1 that has engulfed at least one cellular fragment is plotted as uptake. Data are representative of 30 cells/condition in two independent experiments. In c and d one-way ANOVA followed by Tukey’s post-test. e Tumors were induced by i.v. injection of KP-OVA expressing cells. Cross-presentation by lung cDC1 was detected by flow cytometry on whole lung tissues by labeling with peptide:MHC OVA specific antibody (25D1.16) (gated on CD45+/Cd11c+/Siglech-F−/MHC-IIhigh/CD11b−). Representative histograms and quantification of the percentage of positive cells based on the gate depicted on histograms. Data are from two independent experiments: KP(e) n = 4, KP(l) n = 3 (cDC1 were pooled from two mice for analysis), two-tailed unpaired t-test. f cDC1 were sorted from whole lung cell suspension of early and late KP-OVA bearing tumors and mixed with CFSE-labeled OVA specific T cells (OT-I). Representative CFSE peaks and quantification of proliferation (cells undergoing at least two cycles of proliferation over total T cells). Each point corresponds to cDC1 isolated from KP(e) n = 3 or KP(l) n = 4 mice in three independent experiments, two-tailed unpaired t-test. g CSFE labeled OT-I were transferred into nLung, early, and late tumor bearing animals. OVA-loaded apoptotic thymocytes were administered i.t. and T cell proliferation in the mediastinal lymph node (MLN) was evaluated 2 days later. Data are from two independent experiments, nLung n = 9/7, KP(e) n = 4 or KP(l) n = 7, one-way ANOVA followed by Tukey’s post-test. All data are expressed as mean ± SEM. Source data are provided as a Source Data file.