It's still not clear to me why mass antibody testing would be a game changer, other than for health-workers.

Assumption seems to be that mass testing would limit extent of lockdown, as immune don't need to self-isolate. But 2 problems ->

1) How would immunity be accredited? Without some kind of proof of immunity, once some people leave house, almost all will.

2) If some kind of immunity certificate is issued, there's a massive incentive for young, fit people without the virus to try to catch it.