There’s a danger of PML if the CD4 count gets below 400.
Touch program, and/or Dr. M, monitors CD4 count.
Patient is off of Tysabri if CD4 count is less than 500.
If PML is determined, treatment is plasma exchange 5x over a 10 day period. Steroids are given 10 days after plasma exchange in order to prevent massive brain inflammation from the immune system’s attack on the PML virus (immune system rebound inflammation aka IRIS, actually Immune Reconstitution Inflammatory Syndrome).
I hope this info is helpful.