Tryptophan-immunoadsorption plasmapheresis regulates polymorphonuclear-myeloid-derived suppressor cells and pro-inflammatory cytokines.

Introduction: Immunoadsorption plasmapheresis (IA) has been reported to have immunoregulatory effects, in addition to the removal of autoantibodies. This study aimed to investigate the effects of IA on the proportion of myeloid-derived suppressor cells (MDSCs) that potentially suppress autoimmune responses and regulate immunity.

Methods: The study included 21 patients with autoimmune neurological diseases and 8 healthy participants. We measured polymorphonuclear (PMN)-MDSCs (CD14^-CD11b⁺CD33⁺) and inflammation-related mediators before and after a single session of tryptophan-IA. We also investigated whether an increase in PMN-MDSCs after initial IA was a predictor of clinical efficacy in nine patients with myasthenia gravis based on the Quantitative Myasthenia Gravis score.

Results: For a total of 36 times of IA procedures, the number of PMN-MDSCs significantly increased after IA. Interleukin-10, monocyte chemoattractant protein-1 and macrophage inflammatory protein-1β levels showed significant increases after IA. Despite similar severity at admission, the Quantitative Myasthenia Gravis scores at discharge were significantly lower in the group in which IA increased PMN-MDSCs to a level of 20% of peripheral blood mononuclear cells or more.

Conclusion: Tryptophan-IA regulates PMN-MDSCs and pro-inflammatory cytokines, possibly leading to suppression of autoimmune responses and tissue damage in neuroimmunological disorders.