CD8A and lymphopenia: Different factors, such as concomitant treatment, previous exposure to immunosuppressive drugs and presence of lymphopenia at baseline in a subset of cases, could contribute, at least in part, to this latter finding No significant changes in the numbers of CD4+, CD8+ cells nor in the CD4+/CD8+ ratio over long-term follow-up were observed in another study on MS and NMOSD patients (109).