Human fetal retinal pigment epithelial cells induce apoptosis in the T-cell line Jurkat.
OBJECTIVE
To investigate the mechanism(s) involved in human fetal retinal pigment epithelium (HFRPE)-mediated T-cell death.


METHODS
Pure HFRPE cells were isolated and cultured. Normal and interferon (IFN)-gamma-activated HFRPE from early and late in vitro passages were incubated with cells from the human T-cell leukemia line Jurkat (Jkt). Cultures were pulsed with [3H]-thymidine to measure Jkt cell proliferation. Jkt cells were evaluated for apoptosis either by staining with an ethidium bromide/acridine orange mixture (AO/EB) or with Annexin V-phycoerythrin. The role of Fas ligand (FasL) molecule in HFRPE-mediated apoptosis was assessed by using a mutant Jkt cell line (DD3), which is deficient in Fas-mediated signaling. The involvement of the antiapoptotic human gene bcl-xL was determined by using Jkt cells that were stably transfected with bcl-x(L). The role of cell- cell contact in the induction of apoptosis was evaluated in a transwell system in the presence or absence of neutralizing antibodies against IFN-gamma and tumor necrosis factor (TNF)-alpha.


RESULTS
HFRPE cells inhibited the proliferation of Jkt cells by inducing apoptosis through a FasL-independent pathway. Passaging and IFN-gamma activation strengthened the inhibitory effect of HFRPE cells on the proliferation of Jkt cells. At lower HFRPE passages (P2), bcl-alphaL, overexpression rescued the HFRPE cell-mediated apoptosis. The separation of the cells by the transwell system did not affect the HFRPE cell-mediated suppression. This suppressive effect was not mediated by the secretion of IFN-gamma or TNF-alpha molecules.


CONCLUSIONS
HFRPE cells suppressed the proliferation of Jkt cells by inducing apoptosis. HFRPE cells induced a stronger inhibitory effect on Jkt cells at higher in vitro passages. The HFRPE-induced apoptosis was not mediated through the FasL/Fas pathway or through the secretion of the apoptosis-inducing cytokines IFN-gamma and TNF-alpha. The bcl-xL gene may play a role in preventing HFRPE cell-induced apoptosis in Jkt cells. These combined results suggest that the HFRPE-mediated suppression of primary T cells may also be mediated by the induction of apoptosis. Therefore, the retinal pigment epithelium may play a role in the induction of immune privilege in the subretinal space.
Farrokh-Siar
L
L
Department of Ophthalmology and Visual Science, University of Chicago, Illinois 60637, USA.
Rezai
K A
KA
Semnani
R T
RT
Patel
S C
SC
Ernest
J T
JT
Peterson
E J
EJ
Koretzky
G A
GA
van Seventer
G A
GA
D017209:Apoptosis; D002450:Cell Communication / Q000502:physiology; D002455:Cell Division; D002469:Cell Separation; D002470:Cell Survival; D002478:Cells, Cultured; D018920:Coculture Techniques; D016207:Cytokines / Q000502:physiology; D053222:Fas Ligand Protein; D005333:Fetus / Q000166:cytology*; D005456:Fluorescent Dyes; D005865:Gestational Age; D006801:Humans; D019169:Jurkat Cells / Q000378:metabolism / Q000473:pathology*; D008562:Membrane Glycoproteins / Q000502:physiology; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology; D051020:bcl-X Protein
C494811:BCL2L1 protein, human; D016207:Cytokines; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D005456:Fluorescent Dyes; D008562:Membrane Glycoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein