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Pathogenic Natural Antibodies Recognizing Annexin IV Are Required to Develop Intestinal Ischemia-Reperfusion Injury

ABSTRACT: Intestinal ischemia-reperfusion (IR) injury is initiated when natural IgM antibodies recognize neo-epitopes that are revealed on ischemic cells. The target molecules and mechanisms whereby these neo-epitopes become accessible to recognition are not well understood. Proposing that isolated intestinal epithelial cells (IEC) may carry IR-related neo-epitopes, we used in vitro IEC binding assays to screen hybridomas created from B cells of unmanipulated wild type C57BL/6 mice. We identified a novel IgM monoclonal antibody (mAb B4) that reacted with the surface of IEC by flow cytometric analysis and was alone capable of causing complement activation, neutrophil recruitment and intestinal injury in otherwise IR-resistant Rag1-/- mice. Monoclonal Ab B4 was found to specifically recognize mouse annexin IV. Pre-injection of recombinant annexin IV blocked IR injury in wild type C57BL/6 mice, demonstrating the requirement for recognition of this protein in order to develop IR injury in the context of a complex natural antibody repertoire. Humans were also found to exhibit IgM natural antibodies that recognize annexin IV. These data in toto identify annexin IV as a key ischemia-related target antigen that is recognized by natural Abs in a pathologic process required in vivo to develop intestinal IR injury. Keywords: Natural antibodies, Annexin, Ischemia Reperfusion, Inflammation, Complement

ORGANISM(S): Mus musculus unidentified

PROVIDER: GSE14862 | GEO | 2009/02/19

SECONDARY ACCESSION(S): PRJNA112027

REPOSITORIES: GEO

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Project description:Natural antibodies, which arise without known immune exposure, have been described that specifically recognize cells dying from apoptosis but their role in innate immunity remains poorly understood. Herein, we show that the immune response to neo-antigenic determinants on apoptotic thymocytes is dominated by antibodies to oxidation-associated antigens, phosphorylcholine (PC), a head group that becomes exposed during programmed-cell death, and malondialdehyde (MDA), a reactive aldehyde degradation product of polyunsaturated lipids produced following exposure to reactive-oxidation species. While natural antibodies to apoptotic cells in naM-CM-/ve adult mice were dominated by PC and MDA specificities, the amounts of these antibodies were substantially boosted by treatment of mice with apoptotic cells. Moreover, the relative amounts of PC and MDA antibodies was affected by VH gene inheritance. Antibody interactions with apoptotic-cells also mediated the recruitment of C1q, which alone can promote apoptotic-cell phagocytosis by immature dendritic cells. Significantly, IgM-antibodies to both PC and MDA were primary factors in determining the efficiency of serum-dependent apoptotic-cell phagocytosis. Hence, we demonstrate a mechanism by which certain natural antibodies that recognize neo-antigens on apoptotic cells, in naM-CM-/ve mice and those induced by immune exposure to apoptotic-cells, can enhance the functional capabilities of immature dendritic cells for phagocytic engulfment of apoptotic cells. Keywords: Natural antibodies, Inflammation, Complement, Apoptosis In the study presented here, a total of 11 custom-spotted protein slides were hybridized with a T15 IgM monoclonal antibody at three different concentrations, an isotype control IgM, 2 slides were hybridized with serum from naM-QM-^Wve mice, 2 slides incubated with serum from mice immunized with apoptotic cells, 2 slides were incubated with serum from mice immunized with saline, and a negative control slide with no antibody hybridized

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Pathogenic Natural Antibodies Recognizing Annexin IV Are Required to Develop Intestinal Ischemia-Reperfusion Injury

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