Immunoglobulin G1 (IgG1) is the most abundant circulating human antibody and also the most common scaffold for therapeutic monoclonal antibodies (mAbs). The destruction of IgG-coated targets by cell-mediated pathways begins with an interaction between the IgG Fc region and multiple varieties of membrane-bound Fc g receptors (FcgRs) on the surface of leucocytes. This interaction requires the presence of an asparagine-linked (N-)glycan on the Fc. Furthermore, changes to the N-glycan composition are known to affect FcgR binding affinity. Our laboratory studies the role of N-glycosylation on the structure and function of IgG1 Fc and the FcgRs. This seminar will describe our efforts to characterize how the IgG N-glycan impacts affinity for the FcgRs and recent results describing the structural consequence and functional role of FcgR N-glycan composition.