Immunoperoxidase and enzyme-histochemical demonstration of human skin tryptase in cutaneous mast cells in normal and mastocytoma skin.

Trypsin-like proteinase isolated from human skin was localized in cutaneous mast cells using immunoperoxidase and enzyme-histochemical techniques. Skin biopsy specimens were taken from four mastocytoma and four healthy patients. Immunoperoxidase staining was performed with protein A-sepharose purified rabbit polyclonal antibody raised against human skin tryptase and using aminoethylcarbazole as chromogen. The positively stained cells in the dermis were granular in character. Using peptide 4-methoxy-2-naphthylamide substrates (Bz-Arg-MNA, Z-Lys-Arg-MNA, Z-Gly-Arg-MNA, Z-Pro-Arg-MNA and Z-Gly-Pro-Arg-MNA) and Fast Garnet GBC as chromogen the red azo dye was found to precipitate in the cytoplasmic granules of the cutaneous mast cells. The enzymatic reaction was totally inhibited by diisopropyl fluorophosphate, leupeptin, and benzamidine. No marked inhibition was seen with soybean trypsin inhibitor and alpha-1-anti-trypsin. The best substrate was Z-Gly-Pro-Arg-MNA giving the strongest red azo dye when incubation time was 15, 30 or 60 min. These results show the localization of human skin tryptase in dermal mast cells and the usefulness of Z-Gly-Pro-Arg-MNA as a suitable substrate tested for enzyme-histochemical localization of mast cells in healthy or mastocytoma skin.