Human IgG Antinuclear Antibodies Induce Pregnancy Loss in Mice by Increasing Immune Complex Deposition in Placental Tissue: In Vivo Study Manuela Veglia 1 , Silvia D’Ippolito 1 , Riccardo Marana 1,2 , Fiorella Di Nicuolo 1 , Roberta Castellani 1 , Valentina Bruno 3 , Alessia Fiorelli 1 , Francesco Ria 4 , Giuseppe Maulucci 5 , Marco De Spirito 5 , Giuseppe Migliara 4 , Giovanni Scambia 1 , Nicoletta Di Simone 1 1 Department of Obstetrics and Gynecology, Policlinico A. Gemelli, Universit a Cattolica Del Sacro Cuore, Rome, Italy; 2 International Scientific Institute Paolo VI, ISI, Universit a Cattolica Del Sacro Cuore, Policlinico A. Gemelli, Rome, Italy; 3 Section of Gynecology and Obstetrics, Department of Surgical Sciences, Universit a di Tor Vergata, Rome, Italy; 4 Institute of General Pathology, Universit a Cattolica Del Sacro Cuore, Policlinico A. Gemelli, Rome, Italy; 5 Institute of Physics, Universit a Cattolica Del Sacro Cuore, Rome, Italy Keywords Antinuclear antibodies, complement activation, recurrent pregnancy loss Correspondence Nicoletta Di Simone, Department of Obstetrics and Gynecology, Universit a Cattolica Del Sacro Cuore, Policlinico A. Gemelli, Largo Agostino Gemelli 8, 00168 Rome, Italy. E-mail: nicolettadisimone@rm.unicatt.it Submission August 18, 2015; accepted August 24, 2015. Citation Veglia M, D’Ippolito S, Marana R, Di Nicuolo F, Castellani R, Bruno V, Fiorelli A, Ria F, Maulucci G, De Spirito M, Migliara G, Scambia G, Di Simone N. Human IgG antinuclear antibodies induce pregnancy loss in mice by increasing immune complex deposition in placental tissue: in vivo study. Am J Reprod Immunol 2015; 74: 542–552 doi:10.1111/aji.12429 Problem A threefold higher prevalence of antinuclear antibodies (ANA) has been reported in patients with recurrent pregnancy loss (RPL). Nevertheless, the role of ANA in reproductive failure is still unclear. The aim of this study was to investigate the role of ANA during early pregnancy in vivo. Method of study We used pregnant mice treated with immunoglobulin G (IgG) obtained from normal healthy subjects (NHS); ANA + sera of patients with RPL; and ANA + sera from women with uncomplicated pregnancies (HW). Placental immunohistochemical/immunofluorescence staining was per- formed to detect complement and immune complex deposition. ELISA was performed to evaluate complement levels. Results ANA + IgG from RPL women significantly increased embryo resorption rate, reduced C3, and increased C3a serum levels compared to NHS IgG or ANA + -HW IgG. Increased C3 deposition and increased immune com- plex staining in placental tissues from mice treated with ANA + -RPL IgG fraction compared to NHS- and ANA + -HW-IgG-treated mice were found. Conclusion ANA + IgG injection in mice is able to induce fetal resorption and com- plement activation. The presence on placental tissues of immune com- plexes and complement fragments suggests the complement activation as a possible mechanism of placental damage. Background In recent years, several studies discussed the associa- tion between autoantibodies and reproductive failure. Early studies mainly focused on antiphospholipid antibodies, 1–4 while later research showed interest in antithyroid antibodies (ATA) and antinuclear anti- bodies (ANA). 5–11 ANA are a group of autoantibodies that target components of the cell nucleus. They are commonly American Journal of Reproductive Immunology 74 (2015) 542–552 ª 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd 542 ORIGINAL ARTICLE