Natural antibodies as "eat-me" signals for phagocytosis of necrotic cell debris at sites of tissue injury

Natural antibodies (NAbs) are circulating polyreactive immunoglobulins that bind endogenous and exogenous antigens. Here, we investigated the role of NAbs in driving the clearance of necrotic cell debris from injury sites. Using mouse models of liver injury, we observed that IgM and IgG NAbs opsonize necrotic debris in vivo by recognizing common self-molecules such as histones, actin, phosphoinositides and cardiolipin, but not phosphatidylserine. Importantly, mice lacking NAbs presented impaired recovery from liver injury, which was correlated to sustained presence of necrotic debris in the tissue, prolonged inflammation and reduced hepatocellular proliferation. Mechanistically, necrotic debris phagocytosis was dependent on NAbs in vitro and in vivo, and restitution with total immunoglobulins rescued the defective recovery from liver injury in immunodeficient mice. In summary, we showed that NAbs opsonize necrotic cell debris and act as "eat-me" signals for engulfment through Fc{gamma}Rs and CD11b, driving the recovery from tissue injury. HighlightsO_LINatural antibodies opsonize exposed self-antigens upon necrotic cell death. C_LIO_LIThe phagocytosis of necrotic cell debris requires natural antibodies, Fc{gamma}Rs and CD11b. C_LIO_LINatural antibodies drive cellular proliferation and tissue regeneration after liver injury. C_LIO_LITreatment with natural antibodies improves the recovery from liver injury in both immunodeficient and immunocompetent mice. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/533912v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@1ac8a7org.highwire.dtl.DTLVardef@6b7714org.highwire.dtl.DTLVardef@156d7cdorg.highwire.dtl.DTLVardef@720fea_HPS_FORMAT_FIGEXP M_FIG C_FIG