{"id":"6c024e5a-163d-52e1-a0e1-c3355a9ad532","stable_key":"research:activated-xct","predicate":"supports","statement":"Activated human CD4/CD8 T lymphocytes upregulate xCT and cystine uptake after TCR stimulation.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"literature_reviewed:direct_experimental","direction":"positive","is_public":true,"mechanism_event_id":"1015be5f-33a6-50f8-8aac-1167bd482918","mechanism_event_label":"Activated T cells can import cystine; resting cells need separate treatment.","subject":{"id":"aac19cc3-1b68-5ca3-a896-f61184f7320a","slug":"slc7a11","display_name":"SLC7A11","entity_type_key":"protein"},"object":{"id":"609df3aa-110e-54b4-b072-985dc72c81b2","slug":"cystine-uptake","display_name":"cystine uptake","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"1015be5f-33a6-50f8-8aac-1167bd482918","stable_key":"research:activated-xct","event_type":"transport","label":"Activated T cells can import cystine; resting cells need separate treatment.","description":"Activated human CD4/CD8 T lymphocytes upregulate xCT and cystine uptake after TCR stimulation.","status":"active","compartment":null,"participants":[{"entity":{"id":"aac19cc3-1b68-5ca3-a896-f61184f7320a","slug":"slc7a11","display_name":"SLC7A11","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"609df3aa-110e-54b4-b072-985dc72c81b2","slug":"cystine-uptake","display_name":"cystine uptake","entity_type_key":"cellular_process"},"role":"object","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""}]},"contexts":[{"dimension":"cell_type","value_text":"Activated CD4 and CD8 T cells","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"TCR-stimulated human CD4/CD8 lymphocytes","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Not universal basal uptake in resting cells or a selenium supplementation result.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"b2259ce2-6ba9-5b60-b23b-8d3b990e1c3f","evidence_kind":"curated_literature_summary","locator":"lines 1300-1310","start_line":1300,"end_line":1310,"excerpt":"## activated-xct\n\nActivated T cells can import cystine; resting cells need separate treatment.\n\nActivated human CD4/CD8 T lymphocytes upregulate xCT and cystine uptake after TCR stimulation.\n\nOrganism: Homo sapiens\nCell type: Activated CD4 and CD8 T cells\nExperimental model: TCR-stimulated human CD4/CD8 lymphocytes\nLimitations: Not universal basal uptake in resting cells or a selenium supplementation result.\nPrimary reference: [Fluorescence-based measurement of cystine uptake through xCT shows requirement for ROS detoxification in activated lymphocytes](https://pmc.ncbi.nlm.nih.gov/articles/PMC5065394/)","model_system":"TCR-stimulated human CD4/CD8 lymphocytes","directness":"author_interpretation","verification_status":"secondary_verified","notes":"Curated summary; inspect the linked primary papers for original methods and results.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"4f892f13-06ea-5199-a33c-a703f35c80ae","stable_key":"selenium-research-2026-09-17","title":"Selenium: literature corrections and mechanism additions","document_type":"curated_literature_review","citation_label":"Metabolic Ledger literature curation, 17 September 2026; primary papers linked individually","file_path":"","sha256":"0b818b10c1c7120e5caf7f4d4019d7bd025d745692e424f515d3ef903c9ab7f3","revision_id":"80984e03-5f0f-5877-8094-afef7637444e","review_status":"secondary_verified","notes":"Secondary curated summaries of primary experiments, with explicit models and limitations. Not archived primary full text."}}],"relations":[],"conflicts":[],"corrections":[{"id":"3ac902fa-4705-599f-bf57-3cbb0bd20efc","title":"Activated T cells can import cystine","kind":"context_difference","status":"qualified","why":"The blanket inability statement ignores activation-induced xCT uptake in human T cells.","resolution":"Separate resting from activated cells and DC glutathione supply from direct T-cell transport.","created_at":"2026-09-17 07:19:34","record_type":"qualification","display_label":"Source qualification","record_url":"/corrections/3ac902fa-4705-599f-bf57-3cbb0bd20efc","literature_review":{"revision_id":"80984e03-5f0f-5877-8094-afef7637444e","start_line":1614,"end_line":1620,"papers":[{"paper_key":"siska-2016","title":"Fluorescence-based measurement of cystine uptake through xCT shows requirement for ROS detoxification in activated lymphocytes","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC5065394/","doi":"10.1016/j.jim.2016.08.013","year":2016,"model":"TCR-stimulated human CD4/CD8 lymphocytes","summary":"Activated cells increase xCT expression and cystine uptake."},{"paper_key":"yan-2009","title":"Extracellular redox modulation by regulatory T cells","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC2760945/","doi":"10.1038/nchembio.212","year":2009,"model":"Mouse DC/T-cell cocultures","summary":"GSH export and extracellular cleavage provide cysteine."}]},"sides":[{"conflict_id":"3ac902fa-4705-599f-bf57-3cbb0bd20efc","ordinal":0,"label":"Original preserved statement","revision_id":"fbed30e0-1c0d-5b83-8a1f-2867fbe8a5b5","start_line":103,"end_line":103,"quote":"**T cells are metabolically crippled for cysteine.** They express little **xCT (SLC7A11)**, so they can't import cystine, and they have limited capacity to reduce it. Without cysteine there's no GSH, and without GSH the whole TCR redox cycle stalls.","claim_id":null,"source_key":"immune","source_title":"Selenium in immune cells","claim_ids":[]},{"conflict_id":"3ac902fa-4705-599f-bf57-3cbb0bd20efc","ordinal":1,"label":"Literature correction and experimental limits","revision_id":"80984e03-5f0f-5877-8094-afef7637444e","start_line":1614,"end_line":1620,"quote":"## Activated T cells can import cystine\n\nThe blanket inability statement ignores activation-induced xCT uptake in human T cells.\n\nSeparate resting from activated cells and DC glutathione supply from direct T-cell transport.\nPrimary reference: [Fluorescence-based measurement of cystine uptake through xCT shows requirement for ROS detoxification in activated lymphocytes](https://pmc.ncbi.nlm.nih.gov/articles/PMC5065394/)\nPrimary reference: [Extracellular redox modulation by regulatory T cells](https://pmc.ncbi.nlm.nih.gov/articles/PMC2760945/)","claim_id":null,"source_key":"selenium-research-2026-09-17","source_title":"Selenium: literature corrections and mechanism additions","claim_ids":[]}]}],"research":{"topic":"Selenium scientific audit","plain_language":"Activated T cells can import cystine; resting cells need separate treatment.","evidence_scope":"direct_experimental","papers":[{"key":"siska-2016","title":"Fluorescence-based measurement of cystine uptake through xCT shows requirement for ROS detoxification in activated lymphocytes","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC5065394/","doi":"10.1016/j.jim.2016.08.013","year":2016,"model":"TCR-stimulated human CD4/CD8 lymphocytes","summary":"Activated cells increase xCT expression and cystine uptake."}]}}