Among the mechanisms involved in this pro-inflammatory state in PD patients, increased activation of toll-like receptor 4 (TLR4) and monocytes can be highlighted (Zhang et al., 2024; Brown et al., 2023)—characterized by enhanced synthesis of pro-inflammatory cytokines and chemokines (particularly TNF-α, IL-6, IL-8, IL-10) (Zhang et al., 2024; Brown et al., 2023)—along with increased production of neutrophils and natural killer cells, and decreased lymphocyte production (Zhang et al., 2024). Here, TLR4 is linked to Parkinson disease.