They are not stealthy in the heart: embryonic stem cells trigger cell infiltration, humoral and T-lymphocyte-based host immune response.
OBJECTIVE
The in vivo immunogenicity of Embryonic Stem Cells is controversial. At present, there is only in vitro evidence of MHC I expression by this cell population but vivid speculation about their immune-privileged state. The immunology aspect of ESC transplantation deserves thorough investigation.


METHODS
We injected mouse ESC (expressing Green Fluorescent Protein, GFP) into injured myocardium of syngeneic, allogeneic and SCID recipients. Furthermore, we monitored host response for up to 4 weeks post cell transfer. We determined local response (CD 3, CD 11c expression by host cells), MHC I expression by donor cells, MHC-II expression within and around the graft, humoral response of allogeneic hosts using Flow Cytometry and evaluated the hosts' cytokine response using stimulated spleenocytes by means of ELISPOT. Cell survival was estimated by morphometry, by calculating the area of the GFP+ graft over the area of infarction at multiple sections of the harvested heart.


RESULTS
There was significant cellular infiltration into and around the graft consisting of T-lymphocytes (CD3+) and dendritic cells (CD 11c). Infiltration was detectable at 1 week and progressed through 4 weeks following cell transplantation. The humoral Ab response was moderate at 2 weeks but frank at 4 weeks. ELISPOT demonstrated a Th1 pathway of donor specific T-lymphocyte response with strong IFN-gamma and Il-2 production (figure A). MHC I expression was significant within the graft and maximal in the allogeneic groups.


CONCLUSIONS
An immune response against transplanted ESC was demonstrated and the future use of ESC will likely require the use of systemic immunosuppression.
Cardiothoracic Surgery/Falk Research Center, Stanford University Medical School, Stanford, CA, USA.
Theo
T
Kofidis
Jorg Lucas
JL
deBruin
Masashi
M
Tanaka
Monika
M
Zwierzchoniewska
Irving
I
Weissman
Eugenia
E
Fedoseyeva
Axel
A
Haverich
Robert Clayton
RC
Robbins
D000818:Animals; D000917:Antibody Formation; D039521:CD11c Antigen / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D005434:Flow Cytometry; D006086:Graft vs Host Disease / Q000276:immunology*; D049452:Green Fluorescent Proteins; D007150:Immunohistochemistry / Q000379:methods; D007371:Interferon-gamma / Q000276:immunology; D007376:Interleukin-2 / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D009206:Myocardium / Q000276:immunology*; D033581:Stem Cell Transplantation / Q000379:methods; D013234:Stem Cells / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D013997:Time Factors; D014184:Transplantation, Homologous
D039521:CD11c Antigen; D017252:CD3 Complex; D007376:Interleukin-2; D049452:Green Fluorescent Proteins; D007371:Interferon-gamma