Provine, Nicholas M.

AbstractLymph nodes (LNs) are specialized secondary lymphoid tissues essential to the priming and maintenance of adaptive immune responses, including the B cell germinal center response; thus, they are central to immunity. However, the anatomically restricted and time‐resolved nature of immune priming means that sampling disease‐relevant human LNs requires specialized techniques. This article describes the application of ultrasound‐guided fine‐needle aspiration (FNA) to sample LNs, using cervical LNs of the head and neck as an exemplar. This minimally invasive technique allows collection of both immune cells and cell‐free material that are relevant to both neuroimmune diseases and basic lymphatic functions. Downstream use of cellular material can include multiplexed flow cytometry, single‐cell transcriptome sequencing (RNA‐seq), and B cell cultures. The cell‐free supernatant can be used for proteomics or other similar ‘omics approaches. This unit describes collection of samples by FNA as well as processing and storage of samples for downstream assays. © 2024 The Author(s). Current Protocols published by Wiley Periodicals LLC.Basic Protocol 1: Sampling of human cervical lymph nodes by ultrasound‐guided fine‐needle aspirationAlternate Protocol: Sampling of human lymph nodes by ultrasound‐guided fine‐needle aspiration with negative pressureBasic Protocol 2: Processing and storage of human lymph node samples

Abstract In animal models, brain neurodegeneration biomarkers drain into cervical lymph nodes (CLNs), and this drainage function is reduced with ageing. If this occurred in humans, CLNs may provide a readily accessible measure of this aspect of protein clearance. We tested this hypothesis in people using ultrasound-guided fine needle aspiration. We measured amyloid-beta 40 and 42, phosphorylated tau 181 (pTau181), 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 (ii) plasma, CLNs and capillary blood in four healthy volunteers, an optimization cohort. Ultrasound-guided fine needle aspiration was well-tolerated by all participants. In both cohorts, all biomarkers were detected in all plasma and CLN samples, 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 pTau181 (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 may offer a distinct compartment for minimally-invasive measurement of brain clearance and lymphatic drainage, with potential applicability to study of ageing and future clinical trials.