Maternal gatekeepers: How maternal antibody Fc characteristics influence passive transfer and infant protection

About the Authors: Stephanie N. Langel * E-mail: stephanie.langel@duke.edu (SNL); sallie.permar@duke.edu (SRR) Affiliations Duke Human Vaccine Institute, Duke University Medical Center, Durham, North Carolina, United States of America, Department of Pediatrics, Duke University Medical Center, Durham, North Carolina, United States of America ORCID logo http://orcid.org/0000-0002-0467-7874 Claire E. Otero Affiliations Duke Human Vaccine Institute, Duke University Medical Center, Durham, North Carolina, United States of America, Department of Pediatrics, Duke University Medical Center, Durham, North Carolina, United States of America ORCID logo http://orcid.org/0000-0001-7127-2327 David R. Martinez Affiliation: Department of Epidemiology, University of North Carolina at Chapel Hill School of Public Health, Chapel Hill, North Carolina, United States of America Sallie R. Permar * E-mail: stephanie.langel@duke.edu (SNL); sallie.permar@duke.edu (SRR) Affiliations Duke Human Vaccine Institute, Duke University Medical Center, Durham, North Carolina, United States of America, Department of Pediatrics, Duke University Medical Center, Durham, North Carolina, United States of America ORCID logo http://orcid.org/0000-0003-1438-4554 Introduction Maternal antibodies (MatAbs) passively transferred across the placenta and into breast milk are critical for protection against infectious disease and immune development during the first year of life [1]. Fab, antigen-binding fragment; Fc, crystallizable fragment; FcαR, Fc alpha receptor; FcRn, Fc receptor neonatal; FcγR, Fc gamma receptor; IgA, immunoglobulin A; IgG, immunoglobulin G; J-chain, joining chain; pIgR, polymeric immunoglobulin receptor. https://doi.org/10.1371/journal.ppat.1008303.g001 The IgG Fc domain mediates considerable heterogeneity of its effector functions depending on the subclass and glycan profile. IgA, immunoglobulin A; IgG, immunoglobulin G; sIgA2, secretory IgA. https://doi.org/10.1371/journal.ppat.1008303.g002 Do IgA Fc region characteristics influence IgA passive transfer or effector function in breast milk? Studies are needed to define the mechanisms of Fc-mediated IgA effector functions in breast milk, including their interactions with the developing infant microbiome and protection against intestinal viral infections.