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Immuno-Oncology has revolutionized the way we treat cancer. Cell therapy and immune checkpoint inhibitor therapy can lead to durable cancer remission. Immune checkpoint inhibitor therapy removes the inhibitory signals of T cell activation, allowing the immune system to mount an effective anti-tumor response1. Antibodies against Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4, Programmed Death-1 (PD-1), and Programmed Death Ligand-1 (PD-L1) successfully treat many cancers, including melanomas, carcinomas, and non-small cell lung cancer. Immunoassays provide a tool for researchers to gain additional insights for developing treatment options for cancers and autoimmune diseases. Their ability to provide precise and highly sensitive results allows researchers to quantitatively assess the presence and abundance of disease markers, shedding light on the disease's progression and severity.

Table of Contents


Cytotoxic T-Lymphocyte-4 (CTLA-4) plays a well-described immunosuppressive role in the immune system1, specifically in the interaction between T cells and antigen-presenting cells (APCs). CTLA-4 keeps immune responses within a desired physiological range to protect against autoimmunity. CTLA-4 expression at the immunological synapse is upregulated in response to T Cell Receptor (TCR) stimulation, peaking in 2-3 days. It has a higher affinity and is a more avid receptor for B7-1 and B7-2 than the co-stimulatory CD-28. By outcompeting CD-28, CTLA-4 diminishes TCR signaling and attenuates T Cell activation. Tumors take advantage of the immunosuppressive role of CTLA-4 to evade the immune system. By targeting checkpoint proteins such as CTLA-4 with antibodies, investigators can block CTLA-4's co-inhibitory activities and simulate T cell responses that attack tumors. By utilizing a high sensitivity ELISA kit, levels of CTLA-4 can be measured in both healthy and diseased state samples.

IO Checkpoints PD-1
Serum CTLA-4 Cancer Graph


FIGURE 1. Serum CTLA-4 levels in cancer patient samples. Multiple cancer serum patient samples were tested in the Human CTLA-4 Quantikine High Sensitivity ELISA kit (catalog #HSCT40). All sample types were detectable in cancer and healthy patients.

Serum CTLA-4 Autoimmune Disease Graph

FIGURE 2. Serum CTLA-4 levels in autoimmune patient samples. CTLA-4 was quantified in a broad range of autoimmune diseases using the Human CTLA-4 Quantikine High Sensitivity ELISA kit (Catalog #HSCT40). All samples were detectable in autoimmune and healthy patients.


Enlisting a patient’s own immune system to fight cancer has been a longstanding dream for cancer biologists. Immune checkpoint inhibitors targeting molecules like programmed death-ligand 1 (PD-L1) help make the dream a reality and are now transforming today’s cancer therapy. PD-L1 therapy has shifted the approach to cancer treatment due to its durable effects, and its ability to target a broad range of cancers4-6 with manageable toxicity compared to traditional chemotherapy. Current diagnostic tests for PD-L1 use immunohistochemistry (IHC) to score the tumor microenvironment, but results can be inconsistent. With PD-L1 levels varying from different cancer types, an ELISA can provide quantitative results that are consistent, accurate and reliable from one experiment to the next.

PD-L1 levels with PMA treatment

FIGURE 3. PD-L1 levels in glioma cell supernate. PD-L1 was measured using the Human/Cynomolgus Monkey PD-L1/B7-H1Quantikine ELISA Kit (Catalog #DB7H10) and Simple Plex PD-L1 assay (Catalog #SPCKB-PS-003468) in U87-MG, U251-MG, and A172 glioma cell lines. Both assays detect similar fold increases in PD-L1 expression after Phorbol 12-myristate 13-acetate (PMA) treatment.

PD-L1 measurement on lysate treatments

FIGURE 4. PBMC and HDLM-2 cell supernatant PD-L1 levels. PD-L1 levels were measured using the Human/Cynomolgus Monkey PD-L1/B7-H1Quantikine ELISA Kit (Catalog #DB7H10) and the Simple Plex PD-L1 assay (Catalog #SPCKB-PS-003468) in PBMC and HDLM-2 supernate samples. Both assays detect similar fold increase in PD-L1 expression after PMA, IFNγ, or IFNγ + LPS treatment.

Cancer lysate PD-L1 measurement

FIGURE 5. PD-L1 levels in cell lysates and conditioned media. Human prostate cancer cell lysates and conditioned media supernates were analyzed using the Human/Cynomolgus Monkey B7-H1/PD-L1 Quantikine® ELISA (Catalog #DB7H10). The effects of PI 3-K inhibitor, LY294002, on PMA-induced B7-H1/PD-L1 protein expression and release in human cancer cells was investigated. PC-3 and LNCaP, cells, were left untreated (Control), treated with LY294002, PMA, or pretreated with LY294002 and then PMA for 24 hours. PMA treatment increased membrane and soluble B7-H1/PD-L1 concentration in the more aggressive PC-3, but not LNCaP cells.

Additional Immune Checkpoint Assays
CTLA-4 Quantikine High Sensitivity ELISA
Simple Plex Cartridge
PD-L1 Quantikine ELISA
Simple Plex Cartridge
PD-1 QuicKit ELISA
Quantikine ELISA
Tim-3 Quantikine ELISA
Simple Plex Cartridge
Simple Plex Cartridge
Multiplex Assays Immuno-Oncology Performance Panel
XL Cytokine Performance Panel
Discovery Assay


R&D Systems immune checkpoint immunoassays are sensitive, specific, and provide high-quality data so you don’t have to worry about repeating experiments. We have decades of experience manufacturing immunoassays. Count on our immunoassays for consistent and reproducible data. Our immunoassays are regularly tested for lot-to-lot consistency, precision, recovery, and linearity.


Which Immunoassay Best Suits my Needs

Choose R&D Systems™ Luminex® assays to maximize multiplexing capacity and flexibility while maintaining specificity. Leverage Quantikine™ ELISAs, the most trusted name in the market to for accurate and reproducible results. QuicKit ELISAs offer Quantikine-quality data in 90 minutes or less. DuoSet ELISAs are a cost-effect alternative to buying separate antibodies and proteins and optimizing your own assay. Finally, Simple Plex automated immunoassays afford you a higher level of precision to your workflow, getting you data in 90 minutes or less.

Learn More About Bio-Techne's Immunoassay Workflow Solutions

Current and Emerging Immune Checkpoint Targets for Immuno-Oncology Research

Request this ebook to see some of the current and emerging immune checkpoint molecules that are being investigated as potential targets for cancer immunotherapy. This ebook also details products that we offer for studying these molecules.