Neurodegenerative fluid biomarkers are enriched in human cervical lymph nodes

In animal models, brain neurodegeneration biomarkers drain into cervical lymph nodes (CLNs). If this occurred in humans, CLNs may provide a readily accessible source of these biomarkers, draining the site of primary pathology. We tested this hypothesis in discovery and validation cohorts using ultrasound-guided fine needle aspiration (FNA). We measured amyloid-beta 40 and 42, phospho-Tau-181, glial-fibrillary-acidic-protein, and neurofilament-light using single molecule array in CLN aspirates and plasma from: i) a discovery cohort of 25 autoimmune patients, and from ii) plasma, CLNs and capillary blood in four healthy volunteers, an optimisation-validation cohort. FNA was well-tolerated by all participants. In both cohorts, all biomarkers were detected in all plasmas and CLNs, other than neurofilament-light (8/17 of discovery cohort). CLN biomarker concentrations were significantly greater than plasma concentrations for all except neurofilament-light, most markedly for phospho-Tau-181 (266 fold; P <0.02), whose CLN concentrations decreased with age (Spearman r =-0.66, P =0.001). This study presents the first evidence that neurodegenerative biomarkers are detectable in human CLNs. Raised CLN:plasma biomarker ratios suggest their concentration in CLNs, which may offer a sensitive compartment for minimally-invasive sampling in clinical trials. Further, age-associated phospho-Tau-181 reduction with age suggests FNA of CLNs may measure the integrity of brain lymphatic drainage in vivo . ### Competing Interest Statement IK is a paid medical advisor for digital technology companies developing solutions for the early diagnosis and care of dementia (Five Lives Ltd, Cognetivity Ltd and Mantrah Ltd). SDM is listed as an inventor in patent applications concerning meningeal lymphatic function in neurological diseases (University of Virginia Licensing & Ventures Group, and PureTech Ventures LLC). PK has received consulting fees from UCB, Biomunex, AstraZeneca, and Infinitopes. SRI has received honoraria/research support from UCB, Immunovant, MedImmun, Roche, Janssen, Cerebral therapeutics, ADC therapeutics, Brain, CSL Behring, and ONO Pharma; licensed royalties on patent application WO/2010/046716 entitled Neurological Autoimmune Disorders; and has filed two other patents entitled Diagnostic method and therapy (WO2019211633 and US-2021-0071249-A1; PCT application WO202189788A1) and Biomarkers (PCT/GB2022/050614 and WO202189788A1). The remaining authors report no competing interests.