CD4 T-Cell Suppression by Cells from Toxoplasma gondii-Infected Retinas Is Mediated by Surface Protein PD-L1

Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Blvd., Oklahoma City, OK 73104, USA.
Infection and immunity (Impact Factor: 3.73). 05/2010; 78(8):3484-92. DOI: 10.1128/IAI.00117-10
Source: PubMed


In the inflamed retina, CD4+ T cells can cause retinal damage when they are not properly regulated. Since tissue expression of major histocompatibility
complex (MHC) class II and costimulatory molecules is a key mechanism for regulating effector T cells, we tested the hypothesis
that upregulation of these proteins in the retina contributes to the regulation of CD4 T cells. Here we report that in retinas
infected with the protozoan parasite Toxoplasma gondii, MHC class II is upregulated on infiltrating leukocytes as well as on resident retinal cells, including photoreceptors. Flow
cytometric analysis indicated that B7 costimulatory family members (CD80, CD86, ICOS-L, and programmed death ligand 2 [PD-L2])
were not expressed on class II+ cells. In contrast, PD-L1 (also named B7-H1 or CD274) was expressed on the majority of both hematopoietic and resident retinal
MHC class II-expressing cells. Retinal cells from Toxoplasma-infected animals were able to suppress T-cell activation in a PD-L1-dependent manner. Finally, we demonstrate that the expression
of MHC class II and PD-L1 was critically dependent on gamma interferon (IFN-γ) expression. These data suggest that retinal
MHC class II and PD-L1 expression is a novel mechanism by which the retina protects itself from CD4 T-cell-mediated immune
damage in ocular toxoplasmosis and other types of retinal immune responses.

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Available from: John D Ash, Jan 21, 2015
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