While only small foci of inflammatory infiltrate cells with incipient abscess formation were observed in the kidneys of wild type mice (Figure 3B and F), multiple well-organized bigger abscesses exhibiting the typical central zone of a bacterial cluster surrounded by a cuff of inflammatory cells were visible in the kidneys of C5aR1−/− (Figure 3C and G) and C5aR2−/− (Figure 3D and H) mice already at this early time of infection. This evidence concerns the gene C5AR1 and abscess.