I'm using a pure antibody against the binding site with its receptor, using a scale of concentration (strarting from 1:500 to 1:25) and a blocking time of 30', 1h and 2h, but it does not work. In fact, if I stain the blocked cells with the same clone of the antibody, in this case conjugated for flow cytometry, I obtain the same percentage of positive cells than the untreated cell. Some suggestion?