CTLA-4/CD80 | QF-Pro Glossary

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Definition

CTLA-4 on T cells competes with the co-stimulatory receptor CD28 for binding to CD80 (B7-1) and CD86 (B7-2) on antigen-presenting cells. CTLA-4 has higher affinity and delivers inhibitory signals, preventing T cell activation during priming. Ipilimumab blocks this interaction, allowing T cell activation to proceed. Like PD-1/PD-L1, functional engagement rather than expression determines suppressive activity.

Video Segments

Multi-Checkpoint Immune Signatures

Primary

Early Checkpoint

Acts during T cell priming, not effector phase

First ICI

Ipilimumab–Nobel Prize 2018

Competes with CD28

Higher affinity blocks co-stimulation

iFRET-measurable

Interaction state quantifiable in tissue

Checkpoint Timing: Early vs Late

CTLA-4/CD80 acts during T cell priming in lymph nodes–earlier than PD-1/PD-L1Loading..., which acts in peripheral tissues during the effector phase. CTLA-4 is upregulated shortly after T cell activation and competes with the co-stimulatory receptor CD28 for the same ligands.

Because CD28 signaling is required for full T cell activation, CTLA-4 binding effectively aborts the immune response at its initiation. Blocking CTLA-4 allows T cell priming to proceed, generating more activated effector cells.

Simplified

CTLA-4 Acts Early: CTLA-4/CD80 interaction primarily regulates T cell activation in lymph nodes—an early checkpoint in the immune response.

PD-1 Acts Late: PD-1/PD-L1 primarily regulates T cell activity in tissues—a later checkpoint at the tumor site.

This is why combining anti-CTLA-4 and anti-PD-1 can be more effective than either alone.

Ipilimumab: First Checkpoint Inhibitor

Ipilimumab (Yervoy) was the first FDA-approved checkpoint inhibitorLoading... (2011), demonstrating durable survival benefit in metastatic melanoma. This validated the concept that blocking immune checkpointsLoading... could treat cancer.

However, anti-CTLA-4 therapy has significant immune-related adverse events due to its broad effect on T cell activation. Current use is often in combination with anti-PD-1 (nivolumab + ipilimumab), targeting both early and late checkpoints.

Simplified

Historic Achievement: Ipilimumab (anti-CTLA-4) was the first checkpoint inhibitor to show survival benefit in advanced melanoma (2011). It proved the checkpoint blockade concept could work.

Current Use: Often used in combination with anti-PD-1 drugs, especially in melanoma and kidney cancer.

Measuring CTLA-4/CD80 Engagement

Like PD-1/PD-L1, CTLA-4/CD80 function depends on actual molecular engagement–not just expression. iFRETLoading... has been validated for measuring CTLA-4/CD80 interaction in patient tissue samples.

In the 2020 Cancer Research study, both PD-1/PD-L1 and CTLA-4/CD80 interactions were quantified in melanoma and RCC samples, demonstrating the platform's applicability across checkpoint axes.

Simplified

First-Ever Measurement: The 2022 study was the first to measure CTLA-4/CD80 interaction at molecular resolution in patient tissue.

Key Finding: CD80 expression did NOT correlate with CTLA-4/CD80 engagement. Like PD-1/PD-L1, functional interaction provides different information than expression.

QF-Pro Application

Clinically Validated

Clinical Validation: CTLA-4/CD80 interaction quantification by iFRET represents a first-in-field achievement^[4]–the first time this checkpoint pair has been measured at 1-10nm resolution in patient tissue samples.

In the 2022 radiofrequency ablation study, iFRET quantified CTLA-4/CD80 interaction states in lung metastases from colorectal cancer. Validation was performed on a commercial TMA containing 150 cores across NSCLC and SCLC subtypes.

Importantly, CD80 expression did not correlate with CTLA-4/CD80 interaction state (r=-0.134, P=0.632^[4]), confirming that functional engagement provides distinct information from expression levels.

Click citation numbers to view full references in QF-Pro Applications & Clinical EvidenceLoading...

Simplified

What this means: QF-Pro achieved a world-first: measuring CTLA-4/CD80 interaction at molecular resolution in patient tissue. The key finding? Expression levels don't predict interaction–you need to measure the actual engagement to know if the checkpoint is active.

Expression Assessment

CD80/CD86 expression on APCs indicates checkpoint ligand presence. Cannot determine functional engagement with CTLA-4.

Engagement Measurement

iFRET quantifies CTLA-4/CD80 interaction directly, revealing functional checkpoint activity independent of expression levels.

Clinical Applications

MelanomaLoading...: Ipilimumab monotherapy and nivolumab + ipilimumab combination approved
RCC: Nivolumab + ipilimumab first-line for intermediate/poor risk patients
NSCLCLoading...: Combination regimens in first-line setting
iFRETLoading... validation: CTLA-4/CD80 interaction quantified alongside PD-1/PD-L1 in multiple tumor types

Connected Terms

Immune Checkpoint Category Cross-ref Related Learning Path Video
LAG-3/MHC II Category Related Learning Path Video
PD-1/PD-L1 Category Cross-ref Related Learning Path Video
TIGIT/CD155 Category Related Learning Path Video
ICI Category Cross-ref Related
iFRET Cross-ref Related
Melanoma Cross-ref Related
Dendritic Cells Cross-ref Related