Fig. 1.

IR-61 preferentially accumulates in macrophages at infection sites and promotes bacterial clearance. (a)E. coli or PBS was intratracheally administered into the lungs of mice, and then major organs were imaged using a NIR imaging system after i.v. injection of IR-61 at 12, 24, and 120 h (n = 3 mice per group). (b) Staining indicating the IR-61 levels in macrophages (CD11b⁺F4/80⁺), neutrophils (CD11b⁺Gr1⁺), monocytes (CD11b⁺Gr1^low), dendritic cells (DCs) (CD11c⁺Gr1^low), B cells (CD19⁺), and T cells (CD3⁺) isolated from normal lungs and infected lungs (unstained: n = 3 mice; non-infection: n = 5 mice; infection: n = 5 mice). (c) The amount of internalized IR-61 in various immune cells was measured by MFI (infection group: Macrophages vs monocytes p < 0.0001, Macrophages vs DCs p < 0.0001, Macrophages vs neutrophils p < 0.0001, Macrophages vs T cells p < 0.0001, Macrophages vs B cells p < 0.0001; unstained: n = 3 mice; non-infection: n = 5 mice; infection: n = 5 mice). (d) The levels of Tnf, IL-6, IL-1β, and IL-10 in BALF of mice infected with E. coli at 24 h after the treatment with vehicle or IR-61 (Vehicle vs IR-61 p = 0.0017 (Tnf), p = 0.0049 (IL-6), p < 0.0001 (IL-1β), p = 0.0053 (IL-10); n = 5 mice per group). (e) Representative images of H&E-stained lungs of E. coli-infected mice 24 h after the treatment with vehicle or IR-61 (bars represent 250 μm; n = 5 mice per group). (f) CFUs of bacteria in BALF of mice infected with E. coli at 24 h after the treatment with vehicle or IR-61 (Vehicle vs IR-61 p = 0.0009; n = 5 mice per group). Results are presented as the mean ± SD (∗p < 0.05, ∗∗p < 0.01, and ∗∗∗p < 0.001; one-way ANOVA with Bonferroni post-hoc test (graphs in panel c); two-sided Student's t-test (graphs in panels d and f)).