Inhibition of B-cell activation by retinal pigment epithelium.
OBJECTIVE
To determine whether retinal pigment epithelial (RPE) cells can inhibit B-cell activation in vitro.


METHODS
Primary cultured RPE cells were established from normal C57BL/6 mice. Activated target B cells were established from splenic B cells stimulated with anti-mouse CD40 antibody and lipopolysaccharide (LPS) in the presence of recombinant interleukin 4 (rIL-4). B-cell activation was assessed by examining proliferation through [(3)H]-thymidine incorporation or carboxyfluorescein succinimidyl ester dilution, and antibody production was determined by ELISA. Expression of costimulatory molecules and the receptors on B cells was evaluated by flow cytometry. Neutralizing anti-TGFβ antibodies were used in the assay.


RESULTS
Addition of primary cultured RPE cells suppressed B-cell proliferation in response to anti-CD40, LPS, and rIL-4 stimulation. Similarly, antibody production by these activated B cells was suppressed. Suppression of B-cell activation was mediated by a soluble factor because supernatants from cultured RPE cells were sufficient to inhibit B-cell responses. Moreover, TGFβ was identified as the soluble mediator given that RPE-supernatants failed to suppress B-cell activation if pretreated with neutralizing anti-TGFβ antibodies.


CONCLUSIONS
Cultured RPE cells suppress the activation of B cells in vitro. These data support the hypothesis that retinal pigment epithelium has immunosuppressive properties that are capable of suppressing B-cell activation.
Department of Ophthalmology and Visual Science, Tokyo Medical and Dental University Graduate School of Medicine and Dental Sciences, Tokyo, Japan. sunaoph@tmd.ac.jp
Sunao
S
Sugita
Shintaro
S
Horie
Yukiko
Y
Yamada
Manabu
M
Mochizuki
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D019013:CD40 Antigens / Q000276:immunology; D049109:Cell Proliferation; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D007165:Immunosuppression Therapy; D008070:Lipopolysaccharides; D008213:Lymphocyte Activation / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D055213:Retinal Pigment Epithelium / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000276:immunology
D019013:CD40 Antigens; D008070:Lipopolysaccharides; D016212:Transforming Growth Factor beta