{"id":"d5c8f813-e4f0-5bee-81ae-cb52ffc2c230","stable_key":"18100170-a014-51c3-adeb-9dab4162b8cc:cell-recognition","predicate":"context_dependent_observation","statement":"Radioligand assays found specific FTS-binding sites with apparent Kd near 3 nM in 1301 and HSB2 cells; several other tested cell lines lacked comparable binding.","claim_class":"mechanistic","status":"source_recorded","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"e0b57790-6de9-5f2e-bff3-5d0d2c09bf2b","mechanism_event_label":"Radioligand assays found specific FTS-binding sites with apparent Kd near 3 nM in 1301 and HSB2 cells; several other tested cell lines lacked comparable binding.","subject":{"id":"9bac7a31-4b5b-59f2-8dad-39269ddbb8b1","slug":"fts-peptide","display_name":"Zinc-free FTS nonapeptide component","entity_type_key":"peptide"},"object":{"id":"747582ae-3f6e-5105-b204-f1ad4ba1eb93","slug":"human-ftsbinding-lymphoblasts","display_name":"Specific FTS binding in human 1301 and HSB2 lymphoblastoid cells","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"e0b57790-6de9-5f2e-bff3-5d0d2c09bf2b","stable_key":"18100170-a014-51c3-adeb-9dab4162b8cc:cell-recognition-event","event_type":"biochemical_relationship","label":"Radioligand assays found specific FTS-binding sites with apparent Kd near 3 nM in 1301 and HSB2 cells; several other tested cell lines lacked comparable binding.","description":"Historical radioligand experiments found specific FTS-binding sites in the human lymphoblastoid lines **1301 and HSB2**, with an apparent dissociation constant near 3 nM. Several other tested cell lines lacked comparable binding. This supports selective cellular recognition, but does not identify the binding protein or establish a receptor family. The cellular binding constant and the zinc–peptide binding constant above describe different interactions. [Pleau et al., 1980](https://doi.org/10.1073/pnas.77.5.2861)","status":"provisional","compartment":null,"participants":[{"entity":{"id":"9bac7a31-4b5b-59f2-8dad-39269ddbb8b1","slug":"fts-peptide","display_name":"Zinc-free FTS nonapeptide component","entity_type_key":"peptide"},"role":"tested factor","stoichiometry":null,"state_label":"Radiolabeled FTS binding in 1301/HSB2","sequence_order":0,"notes":""},{"entity":{"id":"747582ae-3f6e-5105-b204-f1ad4ba1eb93","slug":"human-ftsbinding-lymphoblasts","display_name":"Specific FTS binding in human 1301 and HSB2 lymphoblastoid cells","entity_type_key":"cellular_process"},"role":"measured outcome","stoichiometry":null,"state_label":"mixed","sequence_order":1,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary bibliographic record and abstract checked; full methods/figures not comprehensively reviewed.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_contrast","value_text":"{\"intervention\": \"Radiolabeled FTS binding in 1301/HSB2\", \"comparator\": \"Other tested cell lines and assay controls\", \"endpoint\": \"Radioligand assays found specific FTS-binding sites with apparent Kd near 3 nM in 1301 and HSB2 cells; several other tested cell lines lacked comparable binding.\", \"effect_direction\": \"mixed\", \"combination\": \"single\", \"conditions\": []}","comparator":null,"unit":null,"notes":"Explicit extracted experimental comparison; source-derived draft.","entity":null},{"dimension":"experimental_model","value_text":"Human lymphoblastoid cell lines; binding protein identity unresolved.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"interpretation_status","value_text":"Source-derived extraction of a fact-checked reference; access is explicit, not independent raw-data verification.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Interpret only within the recorded preparation, exposure and comparator. The complete source passage retains qualifications; unspecified doses/timing have not been extracted here. No clinical efficacy, nutrient deficiency or unique molecular mediation is inferred.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Radioligand assays found specific FTS-binding sites with apparent Kd near 3 nM in 1301 and HSB2 cells; several other tested cell lines lacked comparable binding.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Specific receptors for the serum thymic factor (FTS) in lymphoblastoid cultured cell lines. | 1980 | DOI 10.1073/pnas.77.5.2861 | PMID 6248873 | https://doi.org/10.1073/pnas.77.5.2861","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"source_locator","value_text":"Reviewed reference lines 54-54; exact primary location described in quoted passage where extracted.","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"26500832-86f5-51ad-ac53-b03fa3965d98","evidence_kind":"source_excerpt","locator":"Lines 54-54","start_line":54,"end_line":54,"excerpt":"Historical radioligand experiments found specific FTS-binding sites in the human lymphoblastoid lines **1301 and HSB2**, with an apparent dissociation constant near 3 nM. Several other tested cell lines lacked comparable binding. This supports selective cellular recognition, but does not identify the binding protein or establish a receptor family. The cellular binding constant and the zinc–peptide binding constant above describe different interactions. [Pleau et al., 1980](https://doi.org/10.1073/pnas.77.5.2861)","model_system":"Human lymphoblastoid cell lines; binding protein identity unresolved.","directness":"reported_statement","verification_status":"source_recorded","notes":"Exact excerpt of the retained AI-assisted reviewed reference; primary sources are cited in primary_references and access scope is retained. Not a verbatim quotation from a primary paper.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"e1871d49-9c6b-547b-a1bb-6e2b9270ca89","stable_key":"import-18100170-a014-51c3-adeb-9dab4162b8cc","title":"Thymulin: detailed mechanisms of action (reviewed 3 October 2026)","document_type":"imported_text","citation_label":"Original AI-assisted review of primary studies and, where relevant, official regulatory records. Access level is retained per claim. Corrections, null results and unresolved questions remain explicit. Not publisher full text or independent replication.","file_path":"","sha256":"6e8ed0d7a5e23fc822f2ab418e0c4fb2411c01fcaa330039e8d7d93218cacc88","revision_id":"8c0e3449-9bbd-57c0-bb5e-de83f044f2ac","review_status":"source_recorded","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}