{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,17]],"date-time":"2026-06-17T03:52:31Z","timestamp":1781668351295,"version":"3.54.5"},"publisher-location":"New York, NY","reference-count":16,"publisher":"Springer US","isbn-type":[{"value":"9781071647332","type":"print"},{"value":"9781071647349","type":"electronic"}],"license":[{"start":{"date-parts":[[2025,10,1]],"date-time":"2025-10-01T00:00:00Z","timestamp":1759276800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"},{"start":{"date-parts":[[2025,10,1]],"date-time":"2025-10-01T00:00:00Z","timestamp":1759276800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"}],"content-domain":{"domain":["link.springer.com"],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>\n                    Programmed cell death protein 1 (PD-1) is crucial in inhibiting immune responses by modulating the activity of T cells. We present an in vitro assay that is based on a co-culture of primary immune cells represented by human peripheral blood mononuclear cells (PBMCs), isolated from healthy donors with Chinese hamster ovary-derived cell line (CHO-K1) overexpressing human PD-L1 protein (\n                    <jats:italic>h<\/jats:italic>\n                    PD-L1) and an artificial TCR-activator construct (TCRAct). CHO-K1\/TCRAct\/\n                    <jats:italic>h<\/jats:italic>\n                    PD-L1 cells mimic antigen-presenting cells by activating T cells via the T-cell receptor (TCR) and providing a ligand for the negative immune checkpoint (PD-L1 protein). The two components, PBMCs and CHO-K1\/TCRAct\/\n                    <jats:italic>h<\/jats:italic>\n                    PD-L1 cells, when in co-culture, provide a T-cell activation (TCA) assay, which may be used to test the potency of molecules targeting the PD-1\/PD-L1 immune checkpoint. This method relies on monitoring the activation of helper CD4+ and cytotoxic CD8+ T cells using flow cytometry by analyzing the expression levels of early (CD69), intermediate (CD25 and HLA-DR), and late (PD-1) activation\/exhaustion markers. This is the well-established in vitro co-culture assay in which primary T-cell activation via the TCR is diminished by the concurrent presence of PD-1\/PD-L1 immune checkpoint, which can be blocked resulting in increased expression of T-cell surface markers.\n                  <\/jats:p>","DOI":"10.1007\/978-1-0716-4734-9_6","type":"book-chapter","created":{"date-parts":[[2025,9,30]],"date-time":"2025-09-30T23:18:18Z","timestamp":1759274298000},"page":"85-95","update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["A PD-1\/PD-L1-Sensitive Co-culture-Based Primary T-Cell Activation Assay"],"prefix":"10.1007","author":[{"given":"Justyna","family":"Kocik-Krol","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Malgorzata","family":"Stec","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Maciej","family":"Siedlar","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thanh Hoa","family":"Vo","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sweta","family":"Rani","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lukasz","family":"Skalniak","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2025,10,1]]},"reference":[{"key":"6_CR1","first-page":"1","volume":"13","author":"C Liu","year":"2022","unstructured":"Liu C, Yang M, Zhang D et al (2022) Clinical cancer immunotherapy: current progress and prospects. 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