However, serum sIL2R was only elevated in four of six SAR-PML patients, which agrees with the fact that serum sIL2R is not necessarily elevated in active sarcoidosis patients,35–37 although still more sensitive and specific than ACE.38 IL2R is expressed at the surface of activated T cells and released into the serum. Here, IL2RA is linked to progressive multifocal leukoencephalopathy.