CD274 and infection: Low dose- (LD-) or high dose- (HD-) SA: LD-SA and HD-SA produced lethality of 15 and 70% respectively by 168 h. At 24 h, LD-infected animals exhibited increased lung monocyte PD-L1 expression (p = 0.0002) but lower bacterial counts (p = 0.0002) compared to HD-animals. By 48 h, infection induced lung neutrophil or macrophage PD-L1 expression (p < 0.0001)