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Interaction of Human Immunoglobulin G with CD16 on Natural Killer Cells: Ligand Clearance, FcγRIIIA Turnover and Effects of Metalloproteinases on FcγRIIIA‐Mediated Binding, Signal Transduction and Killing ‡
Author(s) -
Mota G.,
Moldovan I.,
Calugaru A.,
Hirt M.,
Kozma E.,
Galatiuc C.,
Brasoveanu L.,
BoltzNitulescu G.
Publication year - 2004
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1111/j.0300-9475.2004.01398.x
Subject(s) - cd16 , microbiology and biotechnology , chemistry , antibody , cytotoxic t cell , fc receptor , immunoglobulin g , natural killer cell , monoclonal antibody , receptor , biology , biochemistry , antigen , in vitro , immunology , cd3 , cd8
Abstract Human natural killer (NK) cells express low‐affinity Fc immunoglobulin G (IgG) receptor (FcγRIIIA/CD16). The binding of monomeric IgG (mIgG) and F(ab′) 2 fragments of 3G8 anti‐CD16 monoclonal antibody (mAb) to FcγRIIIA was investigated by flow cytometry. Over 90% of NK cells bound endogenous IgG, and during incubation at 37 °C, the FcγRIIIA occupancy decreased slowly. Approximately 90% of NK cells bind mIgG or F(ab′) 2 fragments of 3G8 anti‐CD16 mAb. The calculated half‐time ( T 1/2 ) of in vitro mIgG dissociation from FcγRIIIA was 130 min. By cross‐linking the mIgG ligand with F(ab′) 2 fragments of anti‐human IgG antibody, the T 1/2 decreases to 85 min. In kinetics study, it has been shown that 125 I‐mIgG bound to FcγRIIIA is slowly released in the culture supernatant, maybe eluted at acid pH, or partially internalized and degraded. The binding of IgG to FcγRIIIA was increased by 53.8% on cells cultured in the presence of RU36156, a matrix metalloproteinase (MMP) inhibitor. Furthermore, an increase in phosphorylation of Lyn tyrosine kinase, after cross‐linking of mIgG‐FcγRIIIA complex, was observed on NK cells treated with RU36156. When the FcγRIIIA was occupied by mIgG, the capacity of NK cells to kill K562 target cells was decreased by RU36156, because the MMP inhibitor protects CD16 from proteolysis. Our data demonstrate that binding of mIgG to human NK cells is followed by ligand dissociation and/or internalization, enzymatic degradation and exocytosis. The RU36156 MMP inhibitor protects FcγRIIIA from cleavage, augments NK‐cell activation and may interfere in their killing capacity.