Retinal pigment epithelial cells phagocytosis of T lymphocytes: possible implication in the immune privilege of the eye.
OBJECTIVE
To investigate the capability of retinal pigment epithelium (RPE) cells to phagocytose T lymphocytes and to further analyse the immunobiological consequences of this phagocytosis.


METHODS
Human RPE cells pretreated or not by cytochalasin, a phagocytosis inhibitor, were co-cultured with T lymphocytes for different time points. Phagocytosis was investigated by optic microscopy, electron microscopy, and flow cytometry. T cell proliferation was measured by (3)H thymidine incorporation. RPE interleukin 1beta mRNA expression was quantified by real time PCR.


RESULTS
RPE cells phagocytose apoptotic and non-apoptotic T lymphocytes, in a time dependent manner. This is an active process mediated through actin polymerisation, blocked by cytochalasin E treatment. Inhibition of RPE cell phagocytosis capabilities within RPE-T cell co-cultures led to an increase of lectin induced T cell proliferation and an upregulation of interleukin 1beta mRNA expression in RPE cells.


CONCLUSIONS
It is postulated that T lymphocyte phagocytosis by RPE cells might, by decreasing the total number of T lymphocytes, removing apoptotic lymphocytes, and downregulating the expression of IL-1beta, participate in vivo in the induction and maintenance of the immune privilege of the eye, preventing the development of intraocular inflammation.
Willermain
F
F
Interdisciplinary Research Institute (IRIBHN), Université Libre de Bruxelles, Belgium. fwillermain@hotmail.com
Caspers-Velu
L
L
Nowak
B
B
Stordeur
P
P
Mosselmans
R
R
Salmon
I
I
Velu
T
T
Bruyns
C
C
D000199:Actins / Q000032:analysis; D002455:Cell Division; D002478:Cells, Cultured; D003572:Cytochalasins / Q000494:pharmacology; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D007111:Immunity, Cellular; D007375:Interleukin-1 / Q000032:analysis; D008854:Microscopy, Electron; D010587:Phagocytosis / Q000187:drug effects; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000276:immunology / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes
D000199:Actins; D003572:Cytochalasins; D007375:Interleukin-1; D012333:RNA, Messenger; C007215:cytochalasin E