Extended Data Fig. 4: Monocytes promote T cell activation.

a, Flow cytometry analysis of neutrophils and monocytes from influenza-infected mouse trachea with or without neutrophil depletion. Cells were stained with Ly6C antibody and CD11b antibody (mean ± SEM, n = 4 mice per group). b, Numbers of monocytes (CD11b⁺Ly6C⁺Ly6G⁻) in the influenza-infected mouse trachea with or without neutrophil depletion. Data are presented as the mean ± SEM, n = 4 mice per group. Statistical differences were assessed by nonparametric Mann-Whitney test. c, RFP⁺ monocytes sorted from the trachea and lungs of HKx31-OVA virus-infected CCR2^RFP/+ mice with or without neutrophil depletion were incubated with CD8⁺ T cells isolated from influenza-infected OT-I mouse dLNs. The monocyte-T cell conjugates were measured by microscopy. Conjugation (%); # monocytes bound to CD8⁺ T cells/# total monocytes. n ≥ 3 per group. Statistical differences were assessed by nonparametric Mann-Whitney test. d, Numbers of OT-I CD8⁺ T cells from the dLN and trachea of HKx31-OVA virus-infected WT or CCR2 KO mice. Data are presented as the mean ± SEM, n = 3 mice per group. Statistical differences were assessed by nonparametric Mann-Whitney test. e, Numbers of monocytes (CD11b⁺Ly6C⁺Ly6G⁻) in the influenza-infected trachea of CCR2-DTR and WT mice on day 6 post infection. Diphtheria toxin was injected into both mouse strains on days -1, +1, +3, and +5 post infection. f, Flow cytometry analysis of the production of IFN-γ, TNF, and Granzyme B (Gzm B) in CD8⁺ T cells on day 7 post infection from WT vs. CCR2-DTR influenza-infected mice treated with diphtheria toxin. Statistical differences were assessed by nonparametric Mann-Whitney test.