Complement activation plays an important role in the pathogenesis of renal allograft injury after kidney transplantation. There are three known pathways of complement activation, namely, classical, alternative, and lectin pathways. In renal allograft injury, contradictory results were reported about the role of the lectin pathway activated via mannan binding lectin (MBL). This Commentary discusses the findings by Bay et al. (this issue), who demonstrated a protective role for circulating MBL in the recipient, particularly in non-HLA immunized recipients.