CD4 and progressive multifocal leukoencephalopathy: As depicted in figure 1, both German natalizumab-associated PML cases for whom blood samples were available at the time point of diagnosis exhibited very low intracellular ATP in CD4+-cells (iATP) in the range of the 3rd percentile of healthy controls (235.3 ng/ml; PML 1 nataliz 243.5 ng/ml, PML 2 nataliz 238.9 ng/ml).