Figure 5. IFN-γ and IL-17A play a critical role in protection against pulmonary Y. pestis challenge.

(A) Scheme of neutralization of IFN-γ, IL-17A, or both in Yptb1(pYA5199)-immunized mice. Mice administrated with PBS (sham) were used as control. (B) Survival study with cytokine neutralization. The Yptb1(pYA5199)-immunized mice (n=10 females) were intraperitoneally injected with 200 μg of anti-IFN-γ, anti-IL-17A, or both mAbs and then intranasally challenged with 50 LD₅₀ of Y. pestis. (C) Lung Y. pestis burden in the respective group of mice at 2 dpi. (D) The number of neutrophils and (E) AMs in the BAL fluid. (F) The absolute number of lung neutrophil and (G) AMs in the lung of mice (n=6 females) treated with anti-IFN-γ, anti-IL-17A, anti-IFN-γ/IL-17A, or isotype control antibodies at 2 dpi. (H) The number of CD4⁺ and (I) CD8⁺ T_RM cells in the lungs of mice (n=6 females) treated with the respective antibodies at 2 dpi. (J) Analysis of cytokines and chemokines in the BAL fluid of mice (n=6 females) treated with the respective antibodies at 2 dpi. (K) Representative H&E-stained lung sections of oral Yptb1(pYA5199)-immunized mice treated with anti-IFN-γ, anti-IL-17A, anti-IFN-γ/IL-17A or isotype control antibodies, or sham mice collected at 2 dpi. The black arrow indicates a reduced alveolar lacunar space, while the red arrow indicates a lung lesion or hemorrhage. Each symbol represents a data point obtained from an individual mouse. Data are presented as the mean ± SD. The statistical analysis is described in the Materials and Methods.