Expression and Functionality Study of 9 Toll-Like Receptors in 33 Drug-Naïve Non-Affective First Episode Psychosis Individuals: A 3-Month Study

Toll-like receptors (TLRs) are a pivotal component of the innate immune system that seem to have a role in the pathogenesis of psychosis. The purpose of this work was to compare the expression and functionality of 9 TLRs in three peripheral blood mononuclear cells (PBMCs) (monocytes, B cells, and T cells) between 33 drug-naïve first-episode psychosis (FEP) individuals and 26 healthy volunteers, at baseline and after 3-month of antipsychotic treatment. The expression of TLRs 1–9 were assessed by flow cytometry. For the assessment of the TLR functionality, cells collected in sodium heparin tubes were polyclonally stimulated for 18 h, with different agonists for human TLR1–9. The results of our study highlight the role that TLR5 and TLR8 might play in the pathophysiology of psychosis. We found a lower expression of these receptors in FEP individuals, regarding healthy volunteers at baseline and after 3-month of treatment on the three PBMCs subsets. Most TLRs showed a lower functionality (especially reduced intracellular levels of TNF-α) in patients than in healthy volunteers. These results, together with previous evidence, suggest that individuals with psychosis might show a pattern of TLR expression that differs from that of healthy volunteers, which could vary according to the intensity of immune/inflammatory response.