Expression of CTLA-4 in nonhuman primate lymphocytes and its use as a potential target for specific immunotoxin-mediated apoptosis: results of in vitro studies.
T-cell-mediated immunoregulation is one of the main mechanisms implicated in induction and maintenance of transplantation tolerance. In this regard, deletion or modulation of xeno/alloantigen-specific T cells, as well as blocking of their interactions with other cell populations, are currently being pursued for tolerance induction in humans as well as nonhuman primates. In order to investigate whether cytotoxic T-lymphocyte antigen-4 (CTLA-4) may represent a suitable target for a T cell depletion approach in nonhuman primate models, we analysed CTLA-4 expression in peripheral blood mononuclear cells (PBMCs) from nonhuman primates and the potential role of two anti-CTLA-4 saporin-conjugated immunotoxins. The analysis was performed in PBMCs from 8 cynomolgus monkeys from Philippines and from Mauritius both at protein level by flow cytometry and at transcriptional level by RT-PCR. In addition, the apoptotic role of the immunotoxins was investigated. The results showed that CTLA-4 was expressed at variable levels depending on the origin of the cynomolgus monkeys and the resting or activated cell condition. CTLA-4 was not expressed on resting Mauritius PBMCs and showed a lower up-regulation upon PMA/PHA activation compared to the Philippines PBMCs that expressed CTLA-4 also before activation. Two CTLA-4 RNA transcripts (672 and 550 bp) were detected with levels variations after cell stimulation. Two anti-CTLA-4 immunotoxins induced in vitro apoptosis of activated PBMCs from both sources of cynomolgus monkeys. This is the first report that documents CTLA-4 expression both at protein and transcriptional level by nonhuman primate PBMCs and provides novel perspectives of xeno/allograft rejection immunotherapy based on CTLA-4 targeting.
Palmisano
G L
GL
Immunogenetics Laboratory, National Cancer Research Institute, Genova, Italy.
Tazzari
P L
PL
Cozzi
E
E
Bolognesi
A
A
Polito
L
L
Seveso
M
M
Ancona
E
E
Ricci
F
F
Conte
R
R
Stirpe
F
F
Ferrara
G B
GB
Pistillo
M P
MP
D000818:Animals; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000032:analysis*; D017209:Apoptosis / Q000276:immunology*; D060908:CTLA-4 Antigen; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D019085:Fluorescent Antibody Technique, Direct / Q000379:methods; D007108:Immune Tolerance / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D007166:Immunosuppressive Agents / Q000032:analysis*; D000922:Immunotoxins / Q000276:immunology*; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008252:Macaca fascicularis; D008297:Male; D012313:RNA / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013601:T-Lymphocytes / Q000276:immunology*; D014158:Transcription, Genetic; D015854:Up-Regulation / Q000276:immunology
D015703:Antigens, CD; D000943:Antigens, Differentiation; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; D007075:Immunoglobulin M; D007166:Immunosuppressive Agents; D000922:Immunotoxins; D012313:RNA