title: The contribution of cell surface FcRn in monoclonal antibody serum uptake from the intestine in suckling rat pups.
abstract: The neonatal Fc receptor (FcRn) in intestinal epithelium is the primary mechanism for transfer of maternal immunoglobulin G (IgG) from suckled milk to serum; but the factors contributing to the rapid uptake of IgG are poorly understood. These studies help to determine the contribution of cell surface FcRn in IgG uptake in 2-week-old rat pups by varying local pH and binding conditions. Variants of a human wild-type (WT) IgG monoclonal antibody (mAb WT) were assessed for binding affinity (KD) to rat (r)FcRn at pH 6.0 and subsequent off-rate at pH 7.4 (1/s) by surface plasmon resonance. Selected mAbs were administered intra-intestinally in isoflurane-anesthetized 2-week rat pups. Full length mAb in serum was quantified by immunoassay, (r)FcRn mRNA expression by reverse transcription polymerase chain reaction, and mAb epithelial localization was visualized by immunohistochemistry. After duodenal administration, serum levels of mAb variants correlated with their rFcRn off-rate at pH 7.4, but not their affinity at pH 6.0. The greatest serum levels of IgG were measured when mAb was administered in the duodenum where rFcRn mRNA expression is greatest, and was increased further by duodenal administration in pH 6.0 buffer. More intense human IgG immunostaining was detected in epithelium than the same variant administered at higher pH. These data suggest an increased contribution for cell surface receptor. We conclude that, in the neonate duodenum, receptor off-rates are as important as affinities for FcRn mediated uptake, and cell surface binding of IgG to rFcRn plays contributes to IgG uptake alongside pinocytosis; both of which responsible for increased IgG uptake.
authors.affiliation: Biologics Research, Janssen R&D - Johnson & Johnson, Biotechnology Center of Excellence Spring House, PA, USA.
authors.forename: Philip R
authors.initials: PR
authors.lastname: Cooper
authors.affiliation: Biologics Pharmacology and Toxicology, Janssen R&D - Johnson & Johnson, Biotechnology Center of Excellence Spring House, PA, USA.
authors.forename: Connie M
authors.initials: CM
authors.lastname: Kliwinski
authors.affiliation: Biologics Research, Janssen R&D - Johnson & Johnson, Biotechnology Center of Excellence Spring House, PA, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Perkinson
authors.affiliation: Biologics Research, Janssen R&D - Johnson & Johnson, Biotechnology Center of Excellence Spring House, PA, USA.
authors.forename: Edwin
authors.initials: E
authors.lastname: Ragwan
authors.affiliation: Biologics Research, Janssen R&D - Johnson & Johnson, Biotechnology Center of Excellence Spring House, PA, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Mabus
authors.affiliation: Biologics Research, Janssen R&D - Johnson & Johnson, Biotechnology Center of Excellence Spring House, PA, USA.
authors.forename: Gordon D
authors.initials: GD
authors.lastname: Powers
authors.affiliation: Biologics Research, Janssen R&D - Johnson & Johnson, Biotechnology Center of Excellence Spring House, PA, USA.
authors.forename: Haimanti
authors.initials: H
authors.lastname: Dorai
authors.affiliation: Biologics Research, Janssen R&D - Johnson & Johnson, Biotechnology Center of Excellence Spring House, PA, USA.
authors.forename: Jill
authors.initials: J
authors.lastname: Giles-Komar
authors.affiliation: Biologics Research, Janssen R&D - Johnson & Johnson, Biotechnology Center of Excellence Spring House, PA, USA.
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Hornby
keywords: FcRn; IgG; bioavailability; cell surface receptor; uptake