Immunological protein profiling of first-episode psychosis patients identifies CSF and blood biomarkers correlating with disease severity

•Peripheral immune markers, particularly those interfering with WNT/β-catenin signaling, were significantly higher in first-episode psychosis (FEP) patients compared to healthy controls and correlated with illness severity.•Peripheral immune activation was higher in patients later receiving a schizophrenia diagnosis compared to those not receiving a diagnosis.•In CSF only one protein differed between healthy controls and FEP patients.