EVALUATION OF IMMUNOHISTOCHEMICAL STAINING OF HUMAN DUODENAL ENDOCRINE-CELLS AFTER MICROWAVE ANTIGEN RETRIEVAL

The effect of microwave antigen retrieval on the immunostaining of hum an duodenal endocrine cells in formaldehyde-fixed, paraffin-embedded m aterial was investigated. The sections were immunostained by the avidi n-biotin complex (ABC) and immunogold-silver autometallography (IGSS) methods with and without prior microwave treatment. Dilutions of up to 1:30000 of the following antisera/antibodies were used: anti-chromogr anin A, anti-chromogranin AB, anti-secretin, anti-gastrin, anti-gastri c inhibitory polypeptide, anti-somatostatin and anti-serotonin. The de tection threshold for all the antibodies was lower after antigen retri eval, and the primary antibody could be used in higher dilutions. The dilutions varied for different antibodies and were between two and ten times the optimal dilution without antigen retrieval. At extremely hi gh dilutions of, or without, the primary antibody, non-specific staini ng of some lymphocytes and the mucus of some goblet cells was observed when the avidin method was applied, but not with the immunogold techn ique. This phenomenon was not observed when optimal dilution or a lowe r dilution was used. This seems to have been caused by the binding of the avidin-biotin complex to epitopes in these structures unmasked by microwave treatment when competition with specific binding sites was a bsent.