I'm trying to get an NK assay working and am having difficulties with getting any sort of target cell lysis. I've tried this assay using an LDH release and also by FACS and got nowhere.
So my question is, do YAC-1 cells 'go-off'? Do they become non-responsive to lysis after prolongued periods in culture? I thaw my cells out and use them within 3 passages but I still don't see an effect.
I've treated isolated spleen cells with interferon and that didn't show any improvement either, even though it's meant to greatly enhance the cytolytic activity of NK cells.
Any comments would be much appreciated!