In multiple sclerosis (MS), vitamin D3 influences immune regulation by decreasing pro-inflammatory cytokines (e.g., IL-17, Th1, Th9, Th22 responses) while enhancing DNA repair and antioxidant capacity via pathways such as OGG1, MYH, MTH1, and NRF2. The gene discussed is MUTYH; the disease is multiple sclerosis.