Anti-CD25 monoclonal antibody therapy affects the death signals of graft-infiltrating cells after clinical heart transplantation.
BACKGROUND
To define whether immunosuppressive agents that block the interleukin (IL)-2 pathway could prevent activation-induced cell death of activated T cells in the graft, we measured expression of IL-2, IL-2 receptor alpha chain (CD25), IL-15, Fas, and Fas ligand by real time reverse transcription-polymerase chain reaction in cardiac allografts.


METHODS
We characterized the phenotype of the infiltrating cells (CD3, CD68, CD25) by immunohistochemistry. The proportion of apoptotic graft-infiltrating cells was determined by TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling) staining. We analyzed endomyocardial biopsy specimens from cardiac allograft recipients who were treated with anti-CD25 monoclonal antibody (mAb) induction therapy (daclizumab) or with matching placebo in combination with cyclosporine, steroids, and mycophenolate mofetil.


RESULTS
Treatment with anti-CD25 mAb affected the number of infiltrating CD3 and CD68 cells and the IL-2-regulated apoptotic pathway. During anti-CD25 mAb treatment, significantly lower intragraft IL-2 and CD25 mRNA transcription levels and decreased numbers of CD25+ T cells were found compared with the levels measured in endomyocardial biopsy specimens from placebo-treated patients (5- to 10-fold, P=0.002 and P<0.0001, respectively). In these samples the intragraft mRNA expression levels of IL-15 were also lower (P=0.02). Inhibition of the IL-2 pathway by anti-CD25 mAb therapy was accompanied by reduced mRNA and protein of Fas ligand and not by reduced Fas expression (P=0.001 and P=0.03). TUNEL staining revealed that the proportion of graft-infiltrating cells was lower in the anti-CD25 mAb patient group than the proportion of apoptotic cells in patients receiving placebo (P=0.06).


CONCLUSIONS
Our data suggest that immunosuppressive agents that affect the IL-2 pathway hinder the mechanism of activation-induced cell death by which the immune system eliminates alloreactive cells.
Baan
C C
CC
Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands. c.c.baan@erasmusmc.nl.
Balk
A H M M
AH
van Riemsdijk
I C
IC
Vantrimpont
P J M J
PJ
Maat
A P W M
AP
Niesters
H G M
HG
Zondervan
P E
PE
van Gelder
T
T
Weimar
W
W
D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D061067:Antibodies, Monoclonal, Humanized; D017209:Apoptosis; D016923:Cell Death / Q000502:physiology; D016207:Cytokines / Q000378:metabolism; D000077561:Daclizumab; D053222:Fas Ligand Protein; D005434:Flow Cytometry; D016027:Heart Transplantation; D006801:Humans; D007074:Immunoglobulin G / Q000627:therapeutic use; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D053645:Interleukin-2 Receptor alpha Subunit; D008213:Lymphocyte Activation / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D018121:Receptors, Cytokine / Q000378:metabolism; D018123:Receptors, Interleukin / Q000378:metabolism; D015375:Receptors, Interleukin-2 / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013601:T-Lymphocytes / Q000378:metabolism / Q000473:pathology / Q000502:physiology*; D019014:fas Receptor / Q000378:metabolism
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D016207:Cytokines; C505661:FASLG protein, human; D053222:Fas Ligand Protein; C508017:IL2RA protein, human; D007074:Immunoglobulin G; D007166:Immunosuppressive Agents; D053645:Interleukin-2 Receptor alpha Subunit; D008562:Membrane Glycoproteins; D018121:Receptors, Cytokine; D018123:Receptors, Interleukin; D015375:Receptors, Interleukin-2; D019014:fas Receptor; D000077561:Daclizumab