Enhanced natural killer cell binding and activation by low-fucose IgG1 antibody results in potent antibody-dependent cellular cytotoxicity induction at lower antigen density.
OBJECTIVE
Recent studies have revealed that fucose removal from the oligosaccharides of human IgG1 antibodies results in a significant enhancement of antibody-dependent cellular cytotoxicity (ADCC) via improved IgG1 binding to FcgammaRIIIa. In this report, we investigated the relationship between enhanced ADCC and antigen density on target cells using IgG1 antibodies with reduced fucose.


METHODS
Using EL4 cell-derived transfectants with differential expression levels of exogenous human CC chemokine receptor 4 or human CD20 as target cells, ADCC of fucose variants of chimeric IgG1 antibodies specific for these antigens were measured. We further investigated IgG1 binding to natural killer (NK) cells and NK cell activation during ADCC induction to elucidate the mechanism by which low-fucose IgG1 induces ADCC upon target cells with low antigen expression.


RESULTS
Low-fucose IgG1s showed potent ADCC at low antigen densities at which their corresponding high-fucose counterparts could not induce measurable ADCC. The quantitative analysis revealed that fucose depletion could reduce the antigen amount on target cells required for constant degrees of ADCC induction by 10-fold for CC chemokine receptor 4 and 3-fold for CD20. IgG1 binding to NK cells was increased by ligating IgG1 with clustered antigen, especially for low-fucose IgG1. Up-regulation of an activation marker, CD69, on NK cells, particularly the CD56(dim) subset, in the presence of both the antibody and target cells was much greater for the low-fucose antibodies.


CONCLUSIONS
Our data showed that fucose removal from IgG1 could reduce the antigen amount required for ADCC induction via efficient recruitment and activation of NK cells.
Niwa
Rinpei
R
Tokyo Research Laboratories, Kyowa Hakko Kogyo, Co. Ltd., 3-6-6 Asahi-machi, Machida-shi, Tokyo 194-8533, Japan.
Sakurada
Mikiko
M
Kobayashi
Yukari
Y
Uehara
Aya
A
Matsushima
Kouji
K
Ueda
Ryuzo
R
Nakamura
Kazuyasu
K
Shitara
Kenya
K
D000920:Antibody-Dependent Cell Cytotoxicity; D018951:Antigens, CD20 / Q000378:metabolism*; D019002:CD56 Antigen / Q000378:metabolism*; D005643:Fucose / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism*; D007694:Killer Cells, Natural / Q000276:immunology*; D008223:Lymphoma / Q000378:metabolism / Q000473:pathology; D011485:Protein Binding; D054398:Receptors, CCR4; D019707:Receptors, Chemokine / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D018951:Antigens, CD20; C515354:CCR4 protein, human; D019002:CD56 Antigen; D007074:Immunoglobulin G; D054398:Receptors, CCR4; D019707:Receptors, Chemokine; D005643:Fucose