Human CD34(+) blood cells induce T-cell unresponsiveness to specific alloantigens only under costimulatory blockade.
OBJECTIVE
The immunogenic role of human CD34(+) cells in allogeneic hematopoietic stem cell transplantation is controversial. In this study we tested the role of CD40 and CTLA4 ligands on CD34(+) cell costimulation of HLA-mismatched lymphocytes.


METHODS
An anti-CD40L monoclonal antibody (hu5C8) and/or CTLA4-Ig molecule were used in primary mixed lymphocyte culture (MLC) with irradiated CD34(+) blood cells and allogeneic responders. Then, secondary MLC, cytotoxic activity, and effector cytokine expression and production were measured.


RESULTS
Each reagent was able to reduce anti-CD34(+) cell alloreactivity, but only the combination of the anti-CD40L monoclonal antibody and CTLA4-Ig induced greater than 90% inhibition of T-cell response in primary MLC and prevented generation of cytotoxic T cells when priming with purified CD34(+) cells. Importantly, responder cells activated by allogeneic CD34(+) cells in the presence of anti-CD40L monoclonal antibody and CTLA4-Ig entered a state of antigen-specific unresponsiveness while responding to third party antigen, tetanus toxoid, or phytohemagglutinin, and showed suppression of interferon-gamma and increase of interleukin-10 expression and release. Interestingly, addition of interleukin-2 in secondary MLC did not reverse T-cell anergy.


CONCLUSIONS
The results demonstrate that human CD34(+) blood progenitors stimulate T-cell responses potently and can induce T-cell unresponsiveness only when both B7:CD28 and CD40:CD40L pathways are blocked, with an increase of interleukin-10-producing cells. Therefore, our data allow design of in vivo studies aimed at achieving T-cell tolerance across HLA barriers by using purified CD34(+) cells and costimulatory blockade.
Arpinati
Mario
M
Research Center for Transplant Immunology, Institute of Hematology and Medical Oncology Seràgnoli, University of Bologna, Bologna, Italy.
Terragna
Carolina
C
Chirumbolo
Gabriella
G
Rizzi
Simonetta
S
Urbini
Benedetta
B
Re
Francesca
F
Tura
Sante
S
Baccarani
Michele
M
Rondelli
Damiano
D
D000069594:Abatacept; D000328:Adult; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D017951:Antigen Presentation; D015703:Antigens, CD; D018952:Antigens, CD34 / Q000032:analysis; D000943:Antigens, Differentiation / Q000276:immunology*; D018122:B7-1 Antigen / Q000276:immunology*; D018106:CD28 Antigens / Q000276:immunology*; D019013:CD40 Antigens / Q000276:immunology*; D023201:CD40 Ligand / Q000276:immunology*; D060908:CTLA-4 Antigen; D002478:Cells, Cultured / Q000276:immunology; D017635:Clonal Anergy / Q000276:immunology*; D006680:HLA Antigens / Q000276:immunology; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000276:immunology*; D006648:Histocompatibility; D006801:Humans; D018796:Immunoconjugates / Q000276:immunology / Q000494:pharmacology; D016753:Interleukin-10 / Q000096:biosynthesis; D007519:Isoantigens / Q000276:immunology*; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology*; D007959:Lymphocyte Culture Test, Mixed; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014184:Transplantation, Homologous / Q000276:immunology
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018952:Antigens, CD34; D000943:Antigens, Differentiation; D018122:B7-1 Antigen; D018106:CD28 Antigens; D019013:CD40 Antigens; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; D006680:HLA Antigens; D018796:Immunoconjugates; D007519:Isoantigens; D016753:Interleukin-10; D023201:CD40 Ligand; D000069594:Abatacept