One possible mechanism for the C5a-C5aR1/2-axis effect on LPS-mediated ARDS was described by Bosmann et al. who identified the appearance of histones H3 and H4 in BALF of mice with ARDS triggered upon ligation of C5a to C5aR1 and C5aR2 [50]. Here, C5 is linked to acute respiratory distress syndrome.