Increased peripheral levels of TARC/CCL17 in first episode psychosis patients

Evidence for a link between the pathophysiology of schizophrenia and the immune system is mounting. Altered levels of chemokines in plasma have previously been reported in patients with schizophrenia under antipsychotic medication. Here we aimed to study both peripheral and central chemokine levels in drug-naïve or short-time medicated first episode psychosis (FEP) patients.

We analyzed nine chemokines in plasma and CSF from 41 FEP patients and 22 healthy controls using electrochemiluminescence assay.

In plasma four chemokines; TARC/CCL17, eotaxin/CCL11, MDC/CCL22, IP-10/CXCL10 and in CSF one chemokine; IP-10/CXCL10 showed reliable detection in >50% of the cases. FEP patients displayed increased levels of TARC/CCL17 in plasma compared to healthy controls, 89.6 (IQR 66.2-125.8) pg/mL compared to 48.6 (IQR 28.0-71.7) pg/mL (p = 0.001). The difference was not attributed to confounding factors. Plasma TARC/CCL17 was not associated with PANSS, CGI or GAF scores, neither with cognitive functions. The chemokines eotaxin/CCL11, MDC/CCL22, IP-10/CXCL10 in plasma and IP-10/CXCL10 in CSF did not differ between FEP patients and controls.

In line with a previous study showing that chronic patients with schizophrenia display increased plasma TARC/CCL17 levels, we here found an elevation in FEP patients suggesting a role of TARC/CCL17 in early stages of schizophrenia. The exact mechanism of this involvement is still unknown and future longitudinal studies as well as studies of central and peripheral chemokine levels would be of great interest.