Chi3l1

Human specific enzyme-linked immunosorbent assays (ELISA) were used to validate CCL18, FABP5, PARK7, CKMT1, INPP1, SNCG, CHI3L1, MIF, SCRN1 and CALB2. Samples were thawed on ice and assayed with specific ELISAs as outlined by the manufacturers as follows: CCL18, FABP5 and PARK7 (Abcam, Waltham, MA, USA); CKMT1, INPP1 and SNCG (MyBIOSource, San Diego, CA, USA); CHI3L1 (Quidel Corporation, San Diego, CA, USA), MIF (R&D Systems, Minneapolis, MN, USA); SCRN1 (Abbexa LLC, Sugar Land, TX, USA) and CALB2 (Cloud-Clone Corporation, Houston, TX, USA). CSF was diluted appropriately with sample diluent and assayed in duplicate or singlets. Single determinations were performed where there was a limited amount of CSF. There was a strong correlation (r = 0.93) between the NPX predicted fold-change and the ELISA fold-change for PARK7, CALB2, CHI3L1, MIF and CCL18. All values for CKMT1, INPP1, SCRN1 and SNCG were below the limit of detection. ENO2 levels and corresponding normal values were obtained from Mayo Clinic Laboratories (https://www.mayocliniclabs.com/test-catalog/overview/81796).

We used ELISA to explore the CSF values of the following molecules: activin A (R&D Systems, MN), chitinase 3-like 1 (CHI3L1; Quidel Corporation, San Diego, CA), C3 complement component (Abcam; Cambridge, UK), neurofilament light chains (NfL; Uman Diagnostics, Sweden), programmed death-ligand 1 (PD-L1; R&D Systems), and T-cell immunoglobulin and mucin domain 3 (TIM-3; Bio-Techne, R&D Systems). All assays were run according to the manufacturer’s instructions with the exception of NfL, for which 10 and 50 µl of CSF were assayed for every patient.