Binding of thymoglobulin to natural killer cells leads to cell activation and interferon-gamma production.
Thymoglobulin is an antithymocyte globulin preparation used in hematopoietic stem cell transplantation (HSCT) to prevent rejection and graft-versus-host disease. Because natural killer (NK)-cell alloreactivity improves HSCT outcome, but only in patients receiving thymoglobulin, we investigated the in vitro effects of thymoglobulin on purified NK cells. Thymoglobulin binding to NK cells and NK-cell activation were assessed by flow cytometry. NK surface targets for thymoglobulin were determined by competition inhibition assays using monoclonal antibodies. Chromium 51 (Cr) release assay, Annexin V combined with 7-amino-actinomycin D staining, and carboxyfluorescein diacetate succinimidyl ester staining were used to study cytotoxic activity, apoptosis/cell death, and NK-cell proliferation, respectively. Interferon (IFN)-gamma production was determined by ELISA. Thymoglobulin, thymoglobulin derived-F(ab')2 fragments as well as rabbit IgG bound NK cells, and competed strongly with anti-CD16. Thymoglobulin enhanced the expression of activation (CD69 and NKG2D) and degranulation (CD107a) markers on NK cells. It competed with CD18 binding and decreased NK activity, but not interleukin-15-induced killer activity. Effects on apoptosis/cell death and proliferation were minimal. F(ab')2 fragments and rabbit IgG strongly induced IFN-gamma production by NK cells. Thymoglobulin binds to NK cells by CD16 by its variable and constant regions. The decrease in NK-cell cytotoxic activity is restored by interleukin-15, and contrasts sharply with the induction of activation, degranulation, and IFN-gamma production. These data support the hypothesis that thymoglobulin treatment is required to observe the improvement in HSCT outcome by NK-cell alloreactivity.
Dalle
Jean-Hugues
JH
Unité d'Immuno-Hématologie Pédiatrique, Hôpital Robert Debre, Paris Cedex 19, France.
Dardari
R'kia
R
Menezes
José
J
Cordeiro
Paulo
P
Champagne
Martin A
MA
Duval
Michel
M
D000328:Adult; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000961:Antilymphocyte Serum; D017209:Apoptosis; D016923:Cell Death; D002860:Chromium Radioisotopes / Q000032:analysis; D006084:Graft Rejection / Q000517:prevention & control; D006086:Graft vs Host Disease / Q000517:prevention & control; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D007371:Interferon-gamma / Q000096:biosynthesis*; D007694:Killer Cells, Natural / Q000166:cytology / Q000276:immunology* / Q000502:physiology; D008213:Lymphocyte Activation; D011485:Protein Binding; D011817:Rabbits; D012016:Reference Values
D000911:Antibodies, Monoclonal; D000961:Antilymphocyte Serum; D002860:Chromium Radioisotopes; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D007371:Interferon-gamma; C512542:thymoglobulin