Immunohistochemical Staining of CD8 Protein in Tissue Sections from Patients with Tumors

Immunohistochemistry (IHC) is one of the most useful detection techniques in scientific research and clinical practice. IHC can give researchers a direct view of a target protein or target cells through bi-colored images of histological tissue sections from patients. Cell nuclei are stained with hematoxylin and target proteins are stained via the chromogenic reaction of 3,3',4,4'-Biphenyltetramine tetrahydrochloride (DAB) in classic IHC, which can show both the relative expression level of a target protein and its location within the tissue. The principle utilized in IHC is the specific binding between an antigen and an antibody, which partially guarantees the accuracy of the results. IHC is also widely used to study cell subsets because it can show the exact location of target cell subsets in organs or tissues. This can help us understand their effects and functional mechanisms. Clinical data suggest that T-cell surface glycoprotein CD8 (CD8)+ tumor-infiltrating lymphocytes (TILs) could serve as an indication of the effectiveness of anti-programmed cell death 1 (PD-1) / programmed cell death ligand 1 (PD-L1) therapy in patients with tumors; therefore, IHC staining of CD8 protein to evaluate the CD8+ TILs in tissue sections becomes very important. IHC has several advantages. Samples are more accessible and last for a long time in storage. The reagents and equipment have been commercialized for years. However, there are also limitations. Lymphocyte infiltration into tumors is a dynamic process, and the results of IHC only reflect the infiltration at one specific time point, and not the dynamic changes over time. This disadvantage partly inhibits its clinical application in tumor immunotherapy, which mostly depends on T cell infiltration into the tumor microenvironment.