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Immunol."],"abstract":"Introduction<\/jats:title>The apicomplexan parasite Toxoplasma gondii<\/jats:italic> establishes chronic infection in the central nervous system, including the retina, causing ocular toxoplasmosis (OT). This persistence relies on a fine balance between inflammatory and immunomodulatory mechanisms, especially in the immune-privileged ocular environment. We previously described the immunologic interactions between retinal cells, and particularly the roles of type I and III interferons. In this study, we investigated the regulatory dynamics of PD-L1, a central immunomodulatory receptor on immune cells.<\/jats:p><\/jats:sec>Methods<\/jats:title>We first investigated the mechanisms of PD-L1 regulation and the roles of type I and III interferons in an in vitro T. gondii<\/jats:italic> infection model using mono- and co-culture systems of human microglia, astrocytes, and M\u00fcller cells. We also assessed PD-L1 expression in an outer blood-retina barrier model (oBRB) of differentiated retinal pigmented epithelial (RPE) cells. Additionally, we looked at retinal cell activation, PD-L1 expression and the roles of these interferons in a mouse model of OT.<\/jats:p><\/jats:sec>Results<\/jats:title>Our findings reveal new roles for type I and III interferons in regulating glial cell activation and PD-L1 expression in RPE, M\u00fcller, astrocytes and microglial cells. Notably, M\u00fcller cells, the most abundant glial cells in the retina, showed the highest baseline PD-L1 expression at both the mRNA and protein levels, and responded robustly to interferon stimulation. This points to a more prominent immunoregulatory role for M\u00fcller cells in the retina than previously recognized. Furthermore, we identified a parasite protease-dependent mechanism that reduces PD-L1 expression in our in vitro<\/jats:italic> oBRB model potentially contributing to immune evasion and inflammation during OT. Finally, in a murine model of OT, we demonstrated that PD-L1 expression reached its peak on day 7 post-infection and that interferon neutralization plays a crucial role in regulating both PD-L1 expression and glial activation.<\/jats:p><\/jats:sec>Discussion<\/jats:title>The parasite T. gondii<\/jats:italic> orchestrates the IFN type I and III dependent retinal immune interaction and downregulates PD-L1 in the oBRB by a protease-dependent mechanism, potentially contributing to immune evasion and inflammation in retinal infection. Our results can pave the way to fully elucidate retinal immune networks and PD-L1 regulation mechanisms, offering potential targets for therapeutic interventions in OT and other retinal inflammatory diseases.<\/jats:p><\/jats:sec>","DOI":"10.3389\/fimmu.2025.1607247","type":"journal-article","created":{"date-parts":[[2025,6,17]],"date-time":"2025-06-17T05:28:18Z","timestamp":1750138098000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":3,"title":["Interferons and Toxoplasma gondii shape PD-L1 regulation in retinal barrier cells: the critical role of proteases"],"prefix":"10.3389","volume":"16","author":[{"given":"Benjamin","family":"Geiller","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Camila","family":"Cevallos","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Iuliia","family":"Tsybenko","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lydia","family":"Arnoux","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marie-Paule","family":"Felder-Schmittbuhl","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alexander W.","family":"Pfaff","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2025,6,17]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"134261","DOI":"10.1080\/09273948.2022.2117705","article-title":"Ocular toxoplasmosis","volume":"31","author":"Goh","year":"2023","journal-title":"Ocular Immunol Inflammation"},{"key":"B2","doi-asserted-by":"publisher","first-page":"43452","DOI":"10.1016\/j.immuni.2018.03.014","article-title":"Regulation and function of the PD-L1 checkpoint","volume":"48","author":"Sun","year":"2018","journal-title":"Immunity"},{"key":"B3","doi-asserted-by":"publisher","first-page":"348492","DOI":"10.1128\/IAI.00117-10","article-title":"CD4 T-cell suppression by cells from toxoplasma gondii-infected retinas is mediated by surface protein PD-L1","volume":"78","author":"Charles","year":"2010","journal-title":"Infect Immun"},{"key":"B4","doi-asserted-by":"publisher","DOI":"10.3389\/fimmu.2024.1356216","article-title":"IFNs in host defence and parasite immune evasion during Toxoplasma gondii infections","volume":"15","author":"L\u00fcder","year":"2024","journal-title":"Front Immunol"},{"key":"B5","doi-asserted-by":"publisher","first-page":"90723","DOI":"10.1016\/j.immuni.2019.03.025","article-title":"Shared and distinct functions of type I and type III interferons","volume":"50","author":"Lazear","year":"2019","journal-title":"Immunity"},{"key":"B6","doi-asserted-by":"publisher","first-page":"451","DOI":"10.1016\/j.immuni.2019.07.007","article-title":"Differential activation of the transcription factor IRF1 underlies the distinct immune responses elicited by type I and type III interferons","volume":"51","author":"Forero","year":"2019","journal-title":"Immunity"},{"key":"B7","doi-asserted-by":"publisher","first-page":"4157","DOI":"10.1016\/j.immuni.2019.08.019","article-title":"Why is IFN-\u03bb Less inflammatory? 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