I was doing an over-expression experiment of a gene for a year. It is a surface protein. The biggest trouble is that I can never detect the gene overexpression by western blot. Interestingly, when I stain it with a flow cytometry antibody made recently (I also validate the antibody myself), there is actually a great amount of surface protein detected. Why can't the surface protein be detected by WB? Is the same reason that people detect something like CTLA-4, PD-1 by flow cytometry instead of western blot?