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Programmed cell death protein 1 (PD-1; also called CD279) is one of the co-inhibitory receptors that is expressed on the surface of antigen-stimulated T cells [1].

Normally, PD-L1 expression can be detected on hematopoietic cells including T cells, B cells, macrophages, dendritic cells, mast cells and healthy tissue cells. But PD-L1 can be expressed by tumor cells and tumor stroma. Interaction tumoral PD-L1 with PD-1 stimulates PD-1-mediated T cell inhibition and down regulation of immune response. PD-L1-PD-1 pathway has proven value as a therapeutic target in a large number of malignancies including non-small cell lung cancer [2].

Immunohistochemical staining is a standardized approach to PD-L1 expression in order to distinguish for patients who may benefit from therapies [3]. Virapath PD-L1 analysis provides accurate quantification of positive cell proportion.

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PD-L1, PD-1, Immunotherapy, Lung Cancer, NSCLC, Image Analysis


To obtain H and DAB colour channels of the image the color deconvolution algorithm is used. Nuclei are detected on H channel and nuclei border pixels are evaluated one by one. Nuclei border pixels on DAB channel are analysed according to positive limit value and rate positive or negative.

Quantitative output variables
  • Positive cell count 
  • Negative cell count
  • Positive cell percentage

Step 1: View a PD-L1 stained lung cancer whole slide image at ViraPath. 

Step 2: Outline tumor either manually or automatically using Virapath Tissue Segmentation algorithm. 

Step 3: Select the PD-L1 analysis and calibrate the parameters. 

Step 4: Run the analysis.


[1] Ishida, Y., Agata, Y., Shibahara, K., and Honjo, T. (1992). Induced expression of PD-1, a novel member of the immunoglobulin gene superfamily, upon programmed cell death. EMBO J. 11, 3887–3895.

[2] Sun, C., Mezzadra, R., & Schumacher, T. N. (2018). Regulation and Function of the PD-L1 Checkpoint. Immunity, 48(3), 434–452. 

[3] Patel, S. P., & Kurzrock, R. (2015). PD-L1 Expression as a Predictive Biomarker in Cancer Immunotherapy. Molecular Cancer Therapeutics, 14(4), 847–856.

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