CXCR1 and infection: First, an increased expression of CXCR1 (Figure 6(a)) and more specifically CXCR2 (Figure 6(b)), receptors expressed by neutrophils, was observed during the time of infection in both mice type with significant upregulation at 48 h PI in IL-33 KO mice compared to WT in accordance with increased number of neutrophils as observed previously (Figures 5(a), 5(d), and 5(e)).