Is that not addressed here? Genuine question, I know science journalism sucks, but don’t have the time to dig deeper into learning about immune response.

In their studies, the team led by Morsbach and Landfester examined more than 500 blood samples from patients taken in 2019. “The antibodies formed against PEG attach themselves to the coated nanocarriers, thus counteracting the effect that is actually desired: the nanocarrier becomes visible to the immune system and is removed before it can exert its effect,” explains Katharina Landfester, director of the department.