CD274 and progressive multifocal leukoencephalopathy: Results suggest that PML may result from two nonexclusive mechanisms: (i) an inhibition of the protective response of JCV‐specific T cells as a consequence of the blockade of the PD1‐PDL1 pathway, associated with a lack of compensatory expression of other inhibitory receptors by T cells and (ii) a neuroinflammatory response (PML‐IRIS) that may have contributed to virus reactivation.