Real-time reverse transcription–PCR detection has shown that the expression of CTLA-4 in peripheral blood mononuclear cells (PBMCs) of MS patients was either decreased (54) or unchanged (55).These results, at least, could reflect the trend of CTLA-4 expression in Tregs of MS patients because CTLA-4 is mainly expressed by Tregs in PBMCs. Here, CTLA4 is linked to myeloid sarcoma.