Yes, for the two days of high dose IL-2 every 8 hours, it was pretty bad. My experience was limited to nausea, fever, sweating, and bed-shaking rigors. I've heard that some patients experience hallucinations.
Note: IL-2 was administered after I received my lab-grown white blood cells. It acts as signal to one's immune system to activate. It was used to jumpstart my immune system after it had been replaced.