Western Blot as a Support Technique for Immunohistochemistry to Detect Programmed Cell Death Ligand 1 Expression

Antibody selection and optimization are crucial to guarantee accurate and reproducible results when using such antibodies for applications such as western blot analysis and immunohistochemistry (IHC). This is especially important when selecting good candidate antibodies that will be used for cancer immunotherapy diagnostics and research. In this chapter, we describe a Western Blot technique as support methodology for the selection and validation of Programmed Cell Death Ligand 1 (PD-L1) antibodies that can be subsequently used in immunohistochemistry applications. Western Blot is a sensitive, specific, and widely available protein characterization technique, used for the detection of specific antigens. PD-L1 is a major immune checkpoint protein that mediates antitumor immune suppression and response, which is routinely detected using IHC in formalin-fixed and paraffin-embedded tissues as part of cancer clinical diagnostic workflows. For this reason, it is critical to define and select the best antibody clones and validate them using different techniques in order to have a reliable detection of positive staining when these antibodies are used in IHC.