Figure 29.

Paradoxical weakening of the antigenicity in CSA-II-mediated chromogenic immunostaining when the primary antibody concentration is high. CD4 immunostaining of the pharyngeal tonsil after HIER using CD4 monoclonal antibody diluted at 1:500 (a) and 1:50 (b). Equivocal CD4 staining on the plasma membrane with a high background occurs when the primary antibody concentration is 10 times higher. The background staining was caused by artificial diffusion of the membrane antigen into the cytoplasm.