If only my immune system would attack all the microplastics in my blood.
What would happen during 'attack' is rather a clot forming, not very good ie in your bloodstream. Kind of pearls forming randomly in your body, but the seed would be a piece of plastic instead of a grain of sand, and it would be just your dead immunity cells around it. The chance of getting rid of it gets much smaller. Now why would you want something like that.
The issue with testosterone is that it's linked to an increase in hematocrit (level of red blood cells in blood). There's a band of hematocrit levels that's healthy for donation. If the hematocrit level is too high, it's potentially dangerous to the recipient, but too low a level of hematocrit makes the donation dangerous to the donor. As a result, hematocrit level testing is one of the few tests that they do before every single donation.
These chemicals aren't dangerous, they're present in all humans. No blood clotting is hemophilia, which is also a dangerous condition. Regular blood donation can prevent build-up, and the decrease in hematocrit after blood donation is one of the reasons for the required interval between donations.
Best is if your body ignores the plastic, that would mean the plastic doesn't do anything to you.