Predicting Therapeutic Response to Molecular Hydrogen in Autoimmune Diseases via Immunophenotyping

Autoimmune diseases, such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), are characterized by immune dysregulation that leads to chronic inflammation and organ damage. Current therapeutic strategies—including corticosteroids, immunosuppressants, and biologics—often exhibit variable efficacy and are associated with potential adverse effects. Molecular hydrogen, recognized for its ability to scavenge mitochondrial reactive oxygen species and inhibit the NLRP3 inflammasome, has emerged as a promising adjunctive treatment. However, its immunomodulatory effects remain insufficiently defined. This study aimed to evaluate the immunological effects of molecular hydrogen-assisted therapy (MHAT) on immune cell subsets and to identify potential predictive biomarkers of treatment efficacy. A total of 25 patients with autoimmune diseases who received MHAT were included (RA: n = 14; SLE: n = 7; others: n = 4, including one each with psoriatic arthritis, primary Sjögren's syndrome, immune-related interstitial lung disease, and diffuse idiopathic skeletal hyperostosis). An additional 15 untreated RA patients served as controls for the assessment of MHAT-induced changes in lymphocyte profiles and type 1 regulatory T (Tr1) cells. MHAT was administered orally at a daily dose of 170 mg hydrogen-enriched coral calcium for three months. Immune phenotyping of T cells, B cells, and regulatory T cells was performed using flow cytometry before and after treatment. Among the 108 immune subsets analyzed, 15 exhibited significant changes, including 11 T cell and 4 B cell subsets. Disease-specific immune modulation was observed in RA patients, particularly characterized by increased proportions of programmed cell death protein 1 (PD-1⁺) T cells and Fas⁺ B cells, and a marked reduction in Tr1 cells compared to patients with SLE or other autoimmune diseases. Based on baseline immune profiles and the percent change in fatigue scores (assessed by the Brief Fatigue Inventory, BFI-T), a Hydrogen-assisted Treatment Response Prediction Index (HRPI) was developed, demonstrating strong predictive performance (ROC = 0.9375, p = 0.0118). HRPI values below −0.3 predicted favorable clinical responses, whereas values near zero were associated with poor outcomes. HRPI shows potential as a predictive biomarker for MHAT efficacy and guides personalized autoimmune treatment.