C3 and Sepsis: We employed in vivo models to analyze the contribution of anaphylatoxin receptors to nasal colonization and invasive disease with Nme. While we found no significant contribution of complement in general (C3, C5), or of the ATRs during asymptomatic Nme nasal colonization, we identified a significant contribution of the ATRs to the course of Nme sepsis in mice.