Immunohistochemistry (IHC) is a technique used in histology to visualize specific antigens or proteins in tissues using labeled antibodies. A double stain IHC technique can be used to identify multiple antigens or proteins in the same tissue section.
In this case, the double stain IHC is used to detect Ki-67 and melanin-A in a skin tissue sample. Ki-67 is a protein that is present during active phases of the cell cycle and is commonly used as a marker for cell proliferation. Melanin-A is a pigment that is typically found in melanocytes and can be used to identify the presence of melanoma.
The Ki-67 positive cells will be stained brown due to the DAB chromagen, while the melanin-A positive cells will be stained red due to the red chromagen.