There is nothing, but antibodies may adsorb directly to the polystyrene surface (if we are talking en empty well).

This paper explains various phenomenons:

http://www.sciencedirect.com/science/article/pii/S0022175913003396

It is important to find a proper plate for detection antibodies, e.g. Maxisorp plates seem almost impossible to block properly in order to avoid unspecific binding.