For drugs that I add to J774A.1, I have used complete medium, DMSO, ethanol, PBS and diH2O with success. The question is a little unclear, but if you are asking if you can keep/culture J774A.1 in serum-free medium, I would limit it to less than 2-3 hours. I have done 60-90 minute treatments in serum-free medium in order to precipitate out secreted cytokines without having to deal with serum proteins. As Won mentioned, serum-free for extended duration will cause issues.

Ok... I used RPMI+FBS 10% for prepare 10ng/mL of LPS and induce activation of J774A.1 cell line, but the macrophages don't produce NO2- detectable for Griess reaction... I don't know if the FBS can inhibit the cell activation...