Establishment of Anti-Dog Programmed Cell Death Ligand 1 Monoclonal Antibodies for Immunohistochemistry.

Immune checkpoint blockade therapy has shown successful clinical outcomes in multiple human cancers. In dogs, several types of tumors resemble human tumors in many respects. Therefore, several groups have developed the anti-dog programmed cell death ligand 1 (dPD-L1) monoclonal antibodies (mAbs) and showed efficacy in several canine tumors. To examine the abundance of dPD-L1 in canine tumors, anti-dPD-L1 diagnostic mAbs for immunohistochemistry are required. In this study, we immunized the peptide in the dPD-L1 intracellular domain, and established anti-dPD-L1 mAbs, L 1 Mab-352 (mouse IgG 1 , kappa), and L 1 Mab-354 (mouse IgG 1 , kappa). In enzyme-linked immunosorbent assay, L 1 Mab-352 and L 1 Mab-354 showed high-binding affinity to the dPD-L1 peptide, and the dissociation constants ( K D ) were determined as 6.9 × 10 -10 M and 7.2 × 10 -10 M, respectively. Furthermore, L 1 Mab-352 and L 1 Mab-354 were applicable for the detection of dPD-L1 in immunohistochemical analysis in paraffin-embedded dPD-L1-overexpressed cells. These results indicated that L 1 Mab-352 and L 1 Mab-354 are useful for detecting dPD-L1 in immunohistochemical analysis.