Rho deficiency in innate immune cells protects against IAV infection. (A-C) Neutrophil load (A), protein content (B), and MPO activity (C) in BAL fluid of RhoB KO² or RhoA/B dKO mice 24 hours after in instillation of IAV pHH05 (1 × 10⁶ PFU/kg). (D-F) Neutrophil load (D), chemokine and cytokine release (E), and type I interferon content (F) in the BAL fluid of RhoB KO¹ or RhoA/B dKO mice 72 hours after IAV challenge. (G) CRAMP surface expression on BAL fluid neutrophils derived from RhoB KO² or RhoA/B dKO mice (72 hours). (H) Virus uptake by neutrophils detected as matrix protein M1 (left, flow cytometry histogram; right, quantification) (72 hours). (I) Virus titer in lung tissue 72 hours after IAV infection. (A-I) Data are pooled from 3 experiments. Means ± SEM: (A-C, n = 5), (D-I, n = 7). (A-F,H[right]-I) *P < .05, **P < .01, ***P < .001, ****P < .0001 by unpaired 2-tailed Student t test). (J-K) Weight loss (J) and survival curve (K) of WT¹, RhoB KO², and RhoA/B dKO mice during IAV infection (7 days) (n = 8 per group). Mann-Whitney U rank-sum test for weight loss at 84 hours: RhoB vs RhoA/B, P < .0005; Gehan-Breslow-Wilcoxon test for Kaplan-Meier survival analysis WT¹ vs RhoA/B, P < .0005; RhoB vs RhoA/B, P < .005; WT¹ vs RhoB, P = .5421.