Related Experiment Video

Updated: Jul 12, 2026

A Kinetic Fluorescence-based Ca2+ Mobilization Assay to Identify G Protein-coupled Receptor Agonists, Antagonists, and Allosteric Modulators
07:41

A Kinetic Fluorescence-based Ca2+ Mobilization Assay to Identify G Protein-coupled Receptor Agonists, Antagonists, and Allosteric Modulators

Published on: February 20, 2018

Molecular determinants of inverse agonist activity of biologicals targeting CTLA-4

Wendy A Teft1, Joaquín Madrenas

  • 1FOCIS Centre for Clinical Immunology and Immunotherapeutics, Robarts Research Institute, London, Ontario, Canada.

Journal of Immunology (Baltimore, Md. : 1950)
|September 6, 2007
PubMed

Insights

Certain biologicals targeting T cell receptors can unexpectedly activate T cells. This study reveals how soluble B7.1 Ig or a specific bispecific antibody triggers T cell activation via CTLA-4, providing insights into T cell modulation.

Area of Science:

  • Immunology
  • Molecular Biology
  • Biochemistry

Background:

  • Biologicals targeting CD28 or CTLA-4 can exhibit superagonist or inverse agonist activity, respectively.
  • This unexpected activity poses risks, limiting therapeutic development of these reagents.
  • Understanding the molecular basis of these activities is crucial for fundamental knowledge and therapeutic applications.

Purpose of the Study:

  • To investigate the molecular determinants of inverse agonist activity for ligands targeting CTLA-4.
  • To elucidate the mechanism by which certain biologicals induce T cell activation through CTLA-4.

Main Methods:

  • Ligation of CTLA-4 using soluble B7.1 Ig, B7.2 Ig, and a bispecific single-chain Fv (24:26).
  • Assessing TCR-independent T cell activation.
  • Analyzing the role of CD28 and CTLA-4 expression levels.
  • Investigating molecular events including CTLA-4 oligomerization and signaling via its cytoplasmic domain.

Main Results:

  • Soluble B7.1 Ig and the 24:26 bispecific antibody induced TCR-independent T cell activation upon CTLA-4 ligation.
  • This inverse agonist activity was dependent on CD28 expression and high CTLA-4 expression.
  • Membrane-bound B7.1 or B7.2 did not elicit this response.
  • The activity correlated with the formation of unique dimer-based CTLA-4 oligomers and involved CTLA-4 cytoplasmic domain signaling.

Conclusions:

  • Identified specific conditions and molecular mechanisms underlying inverse agonist activity of CTLA-4 ligands.
  • Provided a framework for predicting and potentially controlling inverse agonist effects of biologicals targeting CTLA-4.
  • The findings have significant implications for the rational design of immunotherapies targeting costimulatory and inhibitory receptors.

More Related Videos

A Flow Cytometry-based Assay to Identify Compounds That Disrupt Binding of Fluorescently-labeled CXC Chemokine Ligand 12 to CXC Chemokine Receptor 406:56

A Flow Cytometry-based Assay to Identify Compounds That Disrupt Binding of Fluorescently-labeled CXC Chemokine Ligand 12 to CXC Chemokine Receptor 4

Published on: March 10, 2018

Use of Single Chain MHC Technology to Investigate Co-agonism in Human CD8+ T Cell Activation12:09

Use of Single Chain MHC Technology to Investigate Co-agonism in Human CD8+ T Cell Activation

Published on: February 28, 2019

Related Concept Videos

The Two-State Receptor Model01:29

The Two-State Receptor Model

The two-state receptor model explains a drug's interaction with receptors, such as G protein-coupled receptors and ligand-gated ion channels, to induce or inhibit a biological response. When no natural ligands are present, a receptor exists in an equilibrium of inactive (Ri) and active (Ra) conformations. The inactive form does not produce a response, while the active form generates a basal effect known as constitutive activity.
The binding affinity of a drug determines its interaction with one...
Drug-Receptor Interaction: Agonist01:25

Drug-Receptor Interaction: Agonist

Agonists are drugs that interact with specific receptors in the body to produce a biological response. When an agonist binds to a receptor, it activates or enhances the receptor's function, leading to physiological effects. The interaction between agonist drugs and receptors is crucial for their therapeutic action in various medical treatments.
Agonists can bind to receptors in different ways. Some agonists bind directly to the receptor's active site, mimicking the endogenous ligand's action.
Drugs for Treatment of Crohn's Disease in IBD Using Biologic Agents: Anti-TNF01:24

Drugs for Treatment of Crohn's Disease in IBD Using Biologic Agents: Anti-TNF

Tumor Necrosis Factor (TNF), a proinflammatory cytokine, contributes significantly to the inflammation seen in Crohn's disease. It exists as soluble TNF and membrane-bound TNF, with actions mediated through TNF receptors (TNFR). TNFR activation leads to the release of proinflammatory cytokines, T-cell activation, collagen production, and leukocyte migration, all contributing to inflammation in Crohn's disease. Anti-TNF monoclonal antibodies, namely infliximab (Remicade), adalimumab (Humira),...
T Cell Activation and Clonal Selection01:22

T Cell Activation and Clonal Selection

T cells are integral to our adaptive immune system, recognizing and effectively responding to foreign antigens. T cell activation and clonal selection are pivotal in orchestrating this immune response. This article elucidates these mechanisms, detailing the roles of cluster of differentiation (CD) markers, major histocompatibility complex (MHC) molecules, costimulatory signals, and the process of clonal selection.
Naive T cells that have not yet encountered an antigen express two primary CD...
Drug-Receptor Interactions01:29

Drug-Receptor Interactions

Drug-receptor interaction describes the binding of receptors by drugs, but not all drug-receptor interactions result in activation and tissue response. For instance, the binding of agonists activates the receptor to generate a cellular reaction, while antagonists bind to receptors without causing their activation.
Several parameters, such as the drug's affinity for its receptor and its efficacy, which is its ability to activate the receptor, determine the drug's effect on the tissue.
Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase01:11

Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase

Genetic polymorphisms in drug targets have emerged as critical determinants of interindividual variability in drug response and toxicity. Pharmacogenomic investigations increasingly focus on identifying these variations to personalize and optimize therapeutic interventions. A drug target may be a receptor, enzyme, or signaling protein involved in pharmacologic responses or disease-related pathways. While early pharmacogenetic studies focused primarily on drug metabolism, current research...