Multiple sclerosis (MS) is a common autoimmune disease in which axon demyelination follows the inflammatory process. We propose that MS pathogenesis involves DNA damage to patients’ lymphocytes caused by oxidative stress. The effectiveness of DNA repair determines the further fate of impaired cells and may influence the clinical course of MS.

We included 30 MS patients and 30 healthy controls. We isolated CD4+ T, CD8+ T, and B cell subsets from peripheral mononuclear blood cells (PBMCs) through magnetic separation. We used an alkaline version of the comet assay, which is a single-cell gel electrophoresis technique to measure DNA repair efficiency. DNA damage was induced by tert-butyl hydroperoxide (TBH), and the level of damage was quantified as fragmented DNA in the tail (% tail DNA). 

We found increased oxidative DNA damage in MS patients’ PBMCs compared to controls (MS-25.3% vs controls-10.6%, p<0,05). Our results showed that MS patients had a higher percentage of oxidative DNA damage in CD8+ T cells (MS-19,32% vs controls-13,59%), and in CD4+ T cells (MS-14,95% vs. controls-11,47%). The level of DNA damage in B cells was similar in both groups (MS-11,44% vs. controls-12,68%). Examination of the repair kinetics revealed that the DNA lesions were more efficiently repaired in controls (p<0.05).