Of note, we detected an overall lower CD99 surface expression on non-naïve CD4+ T cells in the CSF of MS patients compared to NND patients (Fig. 3C). Stratifying CD99 expression on CSF T cells by sex revealed that lower CD99 expression levels in the MS cohort were solely driven by lower expression in male MS patients, while in women there was no difference between MS and NND patients (Fig. 3D). This evidence concerns the gene CD4 and myeloid sarcoma.