TY  - JOUR
AU  - Groeger, Luise M
AU  - Brinke, Kristina Auf dem
AU  - Simou, Amina
AU  - Luedecke, Daniel
AU  - Maier, Hannah B
AU  - Neyazi, Alexandra
AU  - Gallinat, Jürgen
AU  - Bleich, Stefan
AU  - Skripuletz, Thomas
AU  - Konen, Franz F
AU  - Wiltfang, Jens
AU  - Malchow, Berend
AU  - Fitzner, Dirk
AU  - Hansen, Niels
TI  - Serum and cerebrospinal kappa free light chains in psychiatric syndromes with neuronal and paraneoplastic autoantibodies.
JO  - Behavioural brain research
VL  - 496
SN  - 0166-4328
CY  - Amsterdam
PB  - Elsevier
M1  - DZNE-2025-01234
SP  - 115858
PY  - 2026
AB  - Kappa free light chains (KFLC) are a surrogate parameter for intrathecal immunoglobulin G (IgG), immunoglobulin M (IgM) and immunoglobulin A (IgA) synthesis confirming neuroinflammation in the central nervous system (CNS). It is unclear whether KFLC can differentiate primary psychiatric disorders from neural autoantibody-associated psychiatric syndromes.We enrolled 76 patients with psychiatric diagnoses ICD-10 (International Classification of Diseases, 10th revision) (F00-09, F10-19, F20-29, F30-39, F40-49) and cerebrospinal fluid (CSF) as well as blood samples from our biobank. Commercial assays were used to determine neural autoantibodies. KFLC in serum and CSF samples were assessed by nephelometry (Siemens Atellica NEPH 630 analyzer). We calculated the relative intrathecal fraction (IF) of KFLC and the KFLC index using KFLC quotient and albumin quotient. Criteria for autoimmune encephalitis and autoimmune-mediated psychiatric syndromes were evaluated in patients to determine an autoimmune basis for the psychiatric symptoms.Neither the number of patients with elevated KFLC, a KFLC index nor the KFLC IF percentage served as an instrument for differentiating between autoantibody-positive (n = 18) and autoantibody-negative (n = 58) psychiatric patients. Patients with elevated KFLC levels in CSF had a higher proportion of lymphocytes than patients with non-elevated KFLC as a non-significant trend. We observed a non-significant trend towards higher CSF/serum IgM, but no trend for CSF/serum IgA or CSF/serum IgG ratio in patients with elevated KFLC levels than in those with non-elevated KFLC. No probable autoantibody-positive or seronegative autoimmune encephalitis was detected in patients. However, we observed an autoantibody-associated psychiatric syndrome in 6 out of 10 patients with elevated KFLC-IF, and the detection of elevated KFLC improved the diagnosis of probable autoimmune disease in 4 out of 10 patients (40 
KW  - Humans
KW  - Autoantibodies: blood
KW  - Autoantibodies: cerebrospinal fluid
KW  - Female
KW  - Male
KW  - Middle Aged
KW  - Adult
KW  - Mental Disorders: blood
KW  - Mental Disorders: cerebrospinal fluid
KW  - Mental Disorders: immunology
KW  - Mental Disorders: diagnosis
KW  - Aged
KW  - Immunoglobulin kappa-Chains: blood
KW  - Immunoglobulin kappa-Chains: cerebrospinal fluid
KW  - Encephalitis: immunology
KW  - Encephalitis: blood
KW  - Encephalitis: cerebrospinal fluid
KW  - Encephalitis: diagnosis
KW  - Hashimoto Disease: blood
KW  - Hashimoto Disease: cerebrospinal fluid
KW  - Hashimoto Disease: immunology
KW  - Hashimoto Disease: diagnosis
KW  - Biomarkers: blood
KW  - Biomarkers: cerebrospinal fluid
KW  - Young Adult
KW  - Autoantibodies (Other)
KW  - Kappa free light chains (Other)
KW  - Psychiatry (Other)
KW  - Autoantibodies (NLM Chemicals)
KW  - Immunoglobulin kappa-Chains (NLM Chemicals)
KW  - Biomarkers (NLM Chemicals)
LB  - PUB:(DE-HGF)16
C6  - pmid:41038324
DO  - DOI:10.1016/j.bbr.2025.115858
UR  - https://pub.dzne.de/record/281861
ER  -