Question regarding PML

[rsinger]

I keep hearing about the possibility of PML occurring as a result of low lymphocyte count. What about low basophil and eosinophil counts? What role do these have on the possible reactivation of the JC Virus?

I know there was a case of PML in October or November 2015. This patient was taking Tecfidera and had lymphocyte count that was moderately low at 500. This makes me question the other subsets of the total WBC count.

[carriefromMI]

Lymphocytes fight viruses

Those with low lymphocyte counts have a hard time fighting viruses in general because lymphocytes are the white blood cells which specifically target viruses vs bacteria, fungi etc. PLM is caused by an activation or reactivation of the JC virus. It's a virus which is why it's tied to lymphocyte counts and not other types of blood cells