The overall goal of this project was to investigate: (i) the effect of polyspecific soluble immunoglobulins (sIgG) on Natural Killer (NK) cell viability, phenotype and function, both in vitro and ex vivo; and (ii) the role of differences in the Fcγ receptors (FcγRs) repertoire and FCGR gene locus on NK cell function. The results of this research project provide a better understanding of the effects of sIgG on NK cells, in particular the immediate inhibition of NK cytotoxicity, both direct and via antibody-dependent cell-mediated cytotoxicity (ADCC), which was not sustained 3 days following in vivo administration. Furthermore, the observed associations of FCGR genetic variations and functional impairment of ADCC in our pilot study will generate new hypotheses on NK cell-mediated therapeutic effects of polyclonal but also of monoclonal antibody therapies. Detailed knowledge of the patient's NK cell biology and FCGR repertoire will allow in the future to predict the outcome of therapeutic antibody applications and auto- or alloantibody-mediated damage in the fields of transplantation, oncology and autoimmune diseases.