C5 and infection: The quantification of neutrophils (Ly6G+ cells) infiltration into the kidneys of wild type, C5aR1−/− and C5aR2−/− mice is shown in Figure 4E. These observations were very interesting but a bit perplexing since one of the roles of C5a in the host response to pathogens is to contribute to the recruitment of neutrophils to the site of infection.