Figure 3.

Detection of l-histidine decarboxylase (HDC) mRNA by in situ hybridization. The infiltrating leucocytes of the immunized rats (a and b) and the non-immunized rats (c and d) were collected 4 hr after injection of the antigen solution into the air pouch. In situ hybridization for HDC mRNA was performed using a biotin-labelled antisense HDC-specific RNA probe. HDC mRNA expression was visualized by nitro blue tetrazolium (NBT)/5-bromo-4-chloro-3-indolyl-phosphate (BCIP) NBT/BCIP (a and c) using alkaline phosphatase as substrate. The population of leucocytes infiltrating the pouch fluid (collected 4 hr after injection of the antigen solution) from the immunized and the non-immunized rats, was examined by May–Grünwald–Giemsa staining (b and d). Magnification × 200.