Method Profile

Combined IL-2 Luc and IL-2 Luc LTT Immunosuppression Assays

Two human 2H4 reporter-cell assays combine activation-related IL-2 signaling with information about antimitotic effects.

Immune SystemHuman Cell Assays
Two IL-2 Luc LTT response patterns illustrating the OECD guideline’s classification criteria.
Representative IL-2 Luc LTT response patterns used to illustrate the guideline’s classification criteria. (OECD, Test Guideline 444A, Fig. 6, CC BY 4.0)

Research Applications

Contribute in vitro evidence about potential immunosuppression in drug and chemical safety evaluation, alongside other tests.

Model & Design

The same Jurkat-derived 2H4 human T-cell reporter line is used in IL-2 Luc and IL-2 Luc LTT.

Experimental Format

Interpret the two assay results separately, then classify the combination as positive if either assay indicates immunosuppression.

Model Components

  • Component

    Human cell system

    Description

    2H4 reporter cells derived from the Jurkat T-cell line.

  • Component

    Measured functions

    Description

    IL-2 activation-related luciferase signal and an assay reflecting antimitotic/cell-proliferation effects.

  • Component

    Reference substances

    Description

    Extended guideline evaluation of 83 substances, including 46 pharmaceutical drugs and 37 other chemicals.

Measurements & Endpoints

  • Within- and between-laboratory classification reproducibility
  • Combined sensitivity and specificity versus reference classes
  • Applicability-domain exclusions

Analysis

Keep reproducibility and reference-classification performance separate. The reported combined performance is not a drug-only or clinical-risk estimate.

Published Evidence

  • Evidence Scope

    protocol_reported_benchmark

    Study Design

    OECD guideline synthesis of validation and extended reference-classification data.

    Study Sample

    Lead and three independent laboratories; 83 substances in the extended set, with combined classification analyses of 79 and 76 substances under different domain conditions.

    Comparison

    Reference immunosuppression categories and within-/between-laboratory repeat classifications.

    Finding

    Combined sensitivity 88.7% (47/53) and specificity 53.8% (14/26) for 79 substances; after domain considerations, 90.0% (45/50) and 53.8% (14/26) for 76 substances.

    Interpretation & Limits
    • Overall set mixes drugs and other chemicals.
    • Early T-cell receptor signaling and metabolically activated substances may be missed.
    • Hydrophobicity and luciferase interference can confound interpretation.
    • The guideline states that neither assay can identify immunosuppressive effects for chemicals with a lowest observed effect level (LOEL) of 200 μg/L or higher under this test; this is an assay-domain limit, not a clinical dosing threshold.

Sources

  1. OECD (2026). Test No. 444A: In Vitro Immunotoxicity: IL-2 Luc and Il-2 Luc LTT Assays. OECD Guidelines for the Testing of Chemicals, Section 4. OECD Publishing, Paris. Adopted 25 June 2025; corrected and published 2 July 2026. DOI: 10.1787/27b10ba3-en. ↗