MBP and myeloid sarcoma: “MBP-like material” (MBPL) is probably the best studied; immunoreactive MBPL or its fragments can be detected in the CSF during acute exacerbations in 80% of remitting-relapsing MS patients undergoing acute exacerbations.[49–51] CSF MBPL levels rise acutely during the exacerbation and subside over the next 4–6 weeks.