The role of the peripheral immune system in mediating axonal dysfunction in early-stage amyotrophic lateral sclerosis: an age- and sex-based analysis

Amyotrophic lateral sclerosis is characterized by the progressive loss of motor neurons. Early-stage axonal dysfunction, rather than central nervous system injury, plays a key role in the disease process. However, the molecular mechanisms underlying this dysfunction remain unclear. To investigate the relationship between peripheral immune dysregulation and axonal dysfunction in amyotrophic lateral sclerosis, we recruited 372 patients within the first 12 months of sporadic amyotrophic lateral sclerosis onset between January 2018 and May 2024. We collected peripheral immune markers at baseline, including total leukocytes, lymphocytes, monocytes, neutrophils, basophils, eosinophils, and platelets. We also calculated four derived ratios: neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, and systemic immune inflammation index. Multivariate analysis, adjusted for confounding factors, revealed that higher counts of total leukocytes and neutrophils, as well as higher neutrophil-related ratios, including the neutrophil to lymphocyte ratio and the systemic immune inflammation index, were significantly correlated with higher compound muscle action potential scores. Stratified analyses revealed that these associations varied by age and sex. Furthermore, mediation analysis demonstrated that axonal dysfunction plays a significant role in the relationship between immune markers and disease progression. These findings emphasize the critical role that peripheral immune dysregulation plays in amyotrophic lateral sclerosis progression by mediating peripheral nerve injury, particularly in the early stages of the disease. This study highlights the importance of the peripheral nervous system in the early stages of amyotrophic lateral sclerosis and provides new insights into disease mechanisms and potential therapeutic targets.