title: CD73 expression in RPE cells is associated with the suppression of conventional CD4 cell proliferation.
abstract: CD73 is intensively involved in the regulation of immune responses through the conversion of pro-inflammatory ATP to immunosuppressive adenosine. Herein, we clarified whether cells in the retina express CD73 and participate in the regulation of inflammatory eye diseases such as experimental autoimmune uveitis (EAU). First, immunofluorescence staining was performed to compare the distribution of CD73(+) cells in the retinas of EAU-induced and normal B10RIII mice. The results revealed that a layer of cells in the normal retina that was consistent with the location of retinal pigment epithelial (RPE) cells strongly expressing CD73, and the expression was markedly reduced in the presence of EAU. Thereafter, EAU was also induced in C57BL/6 mice by active immunization or adoptive transfer. CD73 expression in isolated RPE cells was assessed by real-time RT-PCR and western blotting, and the catalytic abilities of the cells to convert AMP to adenosine were determined using HPLC analyses. Compared to the normal control, significantly decreased CD73 expression and AMP catalytic ability were found in the RPE cells isolated from inflamed eyes. CD73 expression and activity were also studied in cultured RPE cells treated with different stimuli, such as Toll-like receptor ligands and cytokines. Highly varied functional CD73 expression was observed in RPE cells through cytokines or Toll-like receptor agonist treatments. Finally, whether RPE cells could regulate the immune response, particularly the proliferation of CD4 cells, through surface-expressed CD73 was determined using a two-chamber assay. The robust inhibition of conventional T-cell proliferation was uniquely observed when CD73(+) RPE cells in the upper chamber were in the presence of AMP. To further confirm the function of CD73 in RPE cells, Cd73(-/-) RPE cells were isolated, and CD73-rescued control cells were constructed. CD73(+)Cd73(-/-) RPE, not Cd73(-/-) RPE, significantly suppressed interacted CD4 cells proliferation and cytokine production. Taken together, these data suggest that naive RPE cells suppressed the immune response through their high expression of CD73. The expression of CD73 in RPE cells could be regulated through many factors, and down-regulated CD73 expression attenuated the suppressive effect of RPE on the proliferation of conventional CD4 cells.
authors.affiliation: General Hospital of Tianjin Medical University, Department of Ophthalmology, Tianjin 300052, China.
authors.forename: Song
authors.initials: S
authors.lastname: Chen
authors.affiliation: The 2nd Hospital of Tianjin Medical University, Clinical Laboratory, Tianjin 300211, China.
authors.forename: Shumin
authors.initials: S
authors.lastname: Zhou
authors.affiliation: The Wilmer Eye Institute at Johns Hopkins, Baltimore, MD 21287, USA.
authors.forename: Kai
authors.initials: K
authors.lastname: Zang
authors.affiliation: General Hospital of Tianjin Medical University, Department of Ophthalmology, Tianjin 300052, China.
authors.forename: Fanqiang
authors.initials: F
authors.lastname: Kong
authors.affiliation: Doheny Eye Institute, University of Southern California, CA 90032, USA.
authors.forename: Dongchun
authors.initials: D
authors.lastname: Liang
authors.affiliation: General Hospital of Tianjin Medical University, Department of Ophthalmology, Tianjin 300052, China. Electronic address: phuayan2000@yahoo.com.
authors.forename: Hua
authors.initials: H
authors.lastname: Yan
mesh_terms: D015720:5'-Nucleotidase / Q000235:genetics*; D019264:Adoptive Transfer; D000818:Animals; D001327:Autoimmune Diseases / Q000276:immunology; D015153:Blotting, Western; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D049109:Cell Proliferation; D004195:Disease Models, Animal; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation / Q000502:physiology*; D007165:Immunosuppression Therapy; D008213:Lymphocyte Activation / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D060888:Real-Time Polymerase Chain Reaction; D055213:Retinal Pigment Epithelium / Q000378:metabolism*; D014605:Uveitis / Q000276:immunology; D014611:Vaccination
chemical_list: D015720:5'-Nucleotidase
keywords: CD4 cells; CD73; RPE; inhibition