Is it necessary to take blocking? Or for some specific samples?

Blocking process is required when detecting macrophages, dendritic cells, NK cells. Fc receptors can be expressed on macrophages, dendritic cells, NK cells, etc. In the process of antibody staining in flow assay, Fc segment of FCM antibody will bind to Fc receptors on cell surface, end up with non-specific staining and lead to false positives signals. Antibodies can be incubated directly after blocking without washing.