Author contribution: Kildyushevsky AV — study planning, literature review, extracorporeal photopheresis (transimmunization), data interpretation, manuscript writing; Kotov SV — study planning, literature review, data interpretation, manuscript writing; Sidorova OP — literature review, data acquisition and interpretation, patient assessment using EDSS, manuscript writing; Borodin AV — literature review, data acquisition and interpretation, patient assessment using EDSS, manuscript writing; Bunak MS — literature review, data acquisition and interpretation, MRI, manuscript writing.

Compliance with ethical standards: the study was approved by the Ethics Committee (protocol No. 16 dated 26 November 2020); the informed consent to participation in the study was submitted by all subjects.