Apr 09, 2026
PD-1/PD-L1 Blocking Bioassay Protocol Using Research-Grade Anti-PD-1 Antibodies
- Qi Cheng1
- 1abinScience, AtaGenix Laboratories, Wuhan, China
External link: http:// https://www.abinscience.com
Protocol Citation: Qi Cheng 2026. PD-1/PD-L1 Blocking Bioassay Protocol Using Research-Grade Anti-PD-1 Antibodies. protocols.io https://dx.doi.org/10.17504/protocols.io.q26g7ojxkvwz/v1
License: This is an open access protocol distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Protocol status: Working
We use this protocol and it's working
Created: April 09, 2026
Last Modified: April 09, 2026
Protocol Integer ID: 314755
Keywords: PD-1, CD279, PDCD1, PD-L1, immune checkpoint, blocking assay, bioassay, immuno-oncology, screening therapeutic antibody, therapeutic antibody, antibodies this protocol, blocking bioassay protocol using research, antibody, human pd, bioassay protocol using research, based bioassay, pd, functional blockade
Disclaimer
For research use only. Not for diagnostic or therapeutic purposes.
Abstract
This protocol describes a cell-based bioassay to evaluate the blocking activity of anti-PD-1 antibodies on the PD-1/PD-L1 interaction. The assay uses a reporter cell system to quantify functional blockade of the PD-1 immune checkpoint. This protocol has been optimized for use with abinScience research-grade anti-human PD-1 monoclonal antibodies and is suitable for comparing biosimilar candidates and screening therapeutic antibody clones.
Troubleshooting
Problem
Low fold induction
Solution
Ensure target cells are fully adherent before adding antibody and effector cells. Low confluency reduces PD-L1 surface expression. Also verify effector-to-target ratio is correct.
Problem
High background signal
Solution
Check that assay medium contains only 1% FBS. Higher serum concentrations can increase non-specific reporter activation. Also ensure no-antibody control wells have both target and effector cells.
Problem
Inconsistent EC50 values
Solution
Use fresh antibody dilutions for each experiment. Repeated freeze-thaw cycles degrade antibody activity. Also ensure consistent cell passage numbers for both target and effector
Reagent Preparation
Recommended anti-PD-1 antibodies (abinScience):
- Research Grade Pembrolizumab (Cat# HS870026): https://www.abinscience.com/product/71/2244.html
- Research Grade Nivolumab (Cat# HS870096): https://www.abinscience.com/product/71/1384.html
- Research Grade Cemiplimab (Cat# HS870016): https://www.abinscience.com/product/71/1404.html
Additional reagents:
- PD-1/PD-L1 Blockade Bioassay Kit (e.g., Promega Cat# J1250) or equivalent reporter system
- PD-L1 aAPC/CHO-K1 cells (target cells)
- PD-1 Effector cells (NFAT-RE reporter Jurkat cells)
- Bio-Glo Luciferase Assay Reagent
- Complete assay medium: RPMI 1640 + 1% FBS
- 96-well white flat-bottom plate
Equipment:
- Luminescence plate reader
- CO2 incubator (37°C, 5% CO2)
- Multichannel pipette
Target Cell Plating (Day 1)
1. Thaw PD-L1 aAPC/CHO-K1 cells and resuspend in complete assay medium.
2. Adjust cell density to 4 × 10⁵ cells/mL.
3. Add 100 μL per well (4 × 10⁴ cells/well) into a 96-well white flat-bottom plate.
4. Incubate overnight at 37°C, 5% CO2 for 16–20 hours to allow cell adherence.
Antibody Serial Dilution (Day 2)
1. Prepare a 4× stock solution of anti-PD-1 antibody in assay medium.
2. Recommended top concentration: 40 μg/mL (4× of final 10 μg/mL).
3. Perform 3-fold serial dilutions across 10 points in a separate dilution plate.
4. Include a no-antibody control (medium only) for baseline measurement.
Add Antibody and Effector Cells
1. Remove medium from the target cell plate carefully without disturbing the cell monolayer.
2. Add 40 μL of each antibody dilution to appropriate wells.
3. Thaw PD-1 Effector cells and resuspend at 1.25 × 10⁶ cells/mL in assay medium.
4. Add 40 μL effector cell suspension per well (5 × 10⁴ cells/well).
5. Final effector-to-target ratio is approximately 1.25:1.
6. Incubate at 37°C, 5% CO2 for 6 hours.
Luminescence Detection
1. Equilibrate Bio-Glo Luciferase Assay Reagent to room temperature.
2. Add 80 μL Bio-Glo reagent per well.
3. Incubate at room temperature for 5–15 minutes.
4. Read luminescence on a plate reader (integration time: 0.5–1 second per well).
Data Analysis
1. Calculate fold induction: Fold Induction = RLU(sample) / RLU(no antibody control).
2. Plot fold induction vs. antibody concentration on a log scale.
3. Fit a 4-parameter logistic (4PL) curve to determine EC50.
4. Compare EC50 values across different anti-PD-1 antibody candidates.
Expected results: A dose-dependent increase in luminescence signal indicates successful PD-1/PD-L1 blockade, with fold induction typically ranging from 2× to 15× at saturating antibody concentrations.