Development of an automatic machine for in situ hybridization and immunohistochemistry

An instrument for the automation of in situ hybridization and immunohistochemistry has been developed. This machine is capable of analyzing 20 microscope glass slides via all of the steps required for colorimetric in situ hybridization or immunohistochemistry. The slides are placed specimen-side down on a specialized Teflon slide-holder set in the reaction chamber of the machine. The system uses a unique type of capillary action between the slide and the holder. The holder has two small holes and is designed to apply, incubate and sequentially add and remove reagents from the slide surface. The system performs the complete processes of in situ hybridization and immunohistochemistry from dewaxing to colorization. Some applications were carried out using this instrument. Cultured cells infected with cytomegalovirus, adenovirus, or herpes simplex virus were hybridized with homologous biotinylated probes, and showed strong purple signals with alkaline phosphatase in the presence of nitroblue tetrazolium and 5-bromo-4-chloro-3-indolyl phosphate. Automatic in situ hybridization using other colorimetric detection systems (e.g., peroxidase-labeled probes/diaminobenzidine/H2O2) was also examined in cells infected with Chlamydia trachomatis and in paraffin-embedded hepatic tissue sections from patients with hepatitis. For conventional immunohistochemical staining, formalin-fixed and paraffin-embedded tissues were used. Glial fibrillary acidic protein and gamma-immunoglobulins were detected automatically in human brain white matter and tonsillar tissues, respectively, as peroxidase-based reddish signals. The intensity of staining was equal to that achieved by manual methods.