Influence of amitriptyline therapy on T cell phenotype in chronic pain patients

Chronic pain (CP) is a major health issue globally, affecting millions and resulting in a significant healthcare burden. Although amitriptyline is widely used to manage CP, its immunomodulatory effects during pain therapy, especially on T cell phenotypes, remain unclear. In this study, we explored how amitriptyline alters T cell phenotypes in CP patients. Therefore, we analyzed the expression profile of peripheral T cells from patients suffering from CP before and three months after amitriptyline therapy in comparison to healthy volunteers. Additionally, the impact of amitriptyline on the T cell phenotype was investigated in vitro. Our results revealed that amitriptyline interferes with production of the pro-inflammatory cytokine interferon (IFN)-γ and elevates the anti-inflammatory cytokine interleukin (IL)-10 as well as frequencies of immunosuppressive regulatory T cells, in particular in patients with improved pain after therapy. Hence, amitriptyline therapy affects the adaptive immune response, which might contribute to pain relief through an immune-mediated mechanism.