CD4 and progressive multifocal leukoencephalopathy: Finally, although monitoring changes in the numbers or in the functional profile of circulating JCV-specific CD4 and CD8 T cells after initiating cART appeared promising for PML-IRIS diagnosis, PML-IRIS was not consistently associated with a higher frequency of circulating JCV-specific CD4 or CD8 T cells, suggesting that other T cell subsets play a role in the pathogenesis of PML-IRIS (50).