Inhibition of B-cell activation and antibody production by triggering inhibitory signals via the PD-1/PD-ligand pathway.
The development of donor-reactive antibodies is regarded to be an important barrier limiting long-term outcome of allo- and xenografts. We asked whether enhanced signaling via the co-inhibitory receptor programmed cell death-1 (PD-1; CD279) can downregulate human B-cell activation.



Proliferation of human purified CD19(+) B cells was induced by in vitro stimulation with CpG oligodeoxynucleotides (CpG-B). To induce antibody production, peripheral blood mononuclear cells were co-cultured with the porcine B-cell line L23. Triggering of inhibitory signals via the PD-1 receptor was obtained either using a recombinant agonistic soluble ligand (PD-L1.Ig) or L23 transfectants overexpressing membrane-bound human PD-L1 (CD274; L23-PD-L1 cells).



Stimulation of purified CD19(+) B cells with CpG-B resulted in upregulation of PD-1 and strong proliferation. Addition of PD-L1.Ig significantly reduced B-cell proliferation in a dose-dependent manner. A great proportion (~1%) of human circulating B cells recognizes the epitope galactose-α1,3-galactose-β1,4-N-acetylglucosamine-R (α-gal). Thus, when B cells-in the presence of T cell help-were cocultured with α-gal-expressing L23 cells, anti-gal and anti-L23 antibodies could readily be detected in the culture supernatant. The level of induced antibodies was significantly reduced when stimulation was performed by L23-PD-L1 cells.



Enhancing inhibitory signals may be part of future protocols to better control humoral immunity to allo- and xenografts.
Transplant Laboratory, Department of General- Visceral- and Transplantation Surgery, Hannover Medical School, Hannover, Germany.
Anna
A
Buermann
Transplant Laboratory, Department of General- Visceral- and Transplantation Surgery, Hannover Medical School, Hannover, Germany.
Dorothee
D
Römermann
Transplant Laboratory, Department of General- Visceral- and Transplantation Surgery, Hannover Medical School, Hannover, Germany.
Wiebke
W
Baars
Transplant Laboratory, Department of General- Visceral- and Transplantation Surgery, Hannover Medical School, Hannover, Germany.
Joachim
J
Hundrieser
Transplant Laboratory, Department of General- Visceral- and Transplantation Surgery, Hannover Medical School, Hannover, Germany.
Jürgen
J
Klempnauer
Transplant Laboratory, Department of General- Visceral- and Transplantation Surgery, Hannover Medical School, Hannover, Germany. schwinzer.reinhard@mh-hannover.de.
Reinhard
R
Schwinzer
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D060890:B7-H1 Antigen / Q000276:immunology*; D049109:Cell Proliferation / Q000502:physiology; D002478:Cells, Cultured; D018920:Coculture Techniques; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology*; D061026:Programmed Cell Death 1 Receptor / Q000276:immunology*; D015398:Signal Transduction; D013552:Swine; D013601:T-Lymphocytes / Q000276:immunology
D060890:B7-H1 Antigen; C423236:CD274 protein, human; C105992:PDCD1 protein, human; D061026:Programmed Cell Death 1 Receptor
B cell; PD-1; co-inhibitory molecules; xenotransplantation