Schizophrenia research, cilt.228, ss.462-471, 2021 (SCI-Expanded)
The etiology of psychotic disorders is still unknown, but in a subgroup of patients symptoms might be caused by
an autoimmune reaction. In this study, we tested patterns of autoimmune reactivity against potentially novel
hippocampal antigens. Serum of a cohort of 621 individuals with psychotic disorders and 257 controls were
first tested for reactivity on neuropil of rat brain sections. Brain reactive sera (67 diseased, 27 healthy) were further
tested for antibody binding to glutamic acid decarboxylase (GAD) isotype 65 and 67 by cell-based assay
(CBA). A sub-cohort of 199 individuals with psychotic disorders and 152 controls was tested for the prevalence
of anti-nuclear antibodies (ANA) on HEp2-substrate aswell as for reactivity to double-strandedDNA, ribosomal P
(RPP), and cardiolipin (CL). Incubation of rat brainwith serumresulted in unidentified hippocampal binding patterns
in both diseased and control groups. Upon screeningwith GAD CBA, one of these patternswas identified as
GAD65 in one individual with schizophrenia and also in one healthy individual. Two diseased and two healthy
individuals had low antibody levels targeting GAD67 by CBA. Antibody reactivity on HEp-2-substrate was increased
in patients with schizoaffective disorder, but only in 3 patients did antibody testing hint at a possible diagnosis
of systemic lupus erythematosus. Although reactivity of serum to intracellular antigens might be
increased in patients with psychotic disorder, no specific targets could be identified. GAD antibodies are very
rare and do not seem increased in serum of patients with psychotic disorders.