Which Biological Indicators Are Primarily Monitored During H-Clat? Ensuring Footwear Textile Safety And Compliance

The primary biological indicators monitored during the Human Cell Line Activation Test (h-CLAT) are the cell surface markers CD86 and CD54. To evaluate the safety of footwear textiles, this test utilizes flow cytometry to measure the expression levels of these specific markers on the THP-1 human monocytic cell line.

The h-CLAT methodology relies on measuring the upregulation of CD86 and CD54 as a direct signal of immune system activation. These markers serve as the definitive metric for determining if chemicals in footwear materials possess skin sensitization potential.

The Biological Mechanism of h-CLAT

Monitoring Surface Markers

The core of the h-CLAT lies in tracking the expression of CD86 and CD54.

These are proteins located on the surface of the cell. The test utilizes flow cytometry, a laser-based technology, to quantitatively measure changes in the density of these markers.

The THP-1 Cell Line

The test does not use human tissue directly; instead, it employs the THP-1 human monocytic cell line.

These cells are selected because they act as a reliable biological proxy. When stimulated by chemical substances, THP-1 cells mimic the behavior of immune cells, allowing researchers to predict human biological responses in a controlled laboratory setting.

Evaluating Footwear Safety

Simulating Dendritic Cell Activation

The primary goal of monitoring CD86 and CD54 is to assess the activation state of dendritic cells.

Dendritic cells are the "sentinels" of the immune system. When the THP-1 cells show increased expression of CD86 and CD54, it reflects the process that occurs when dendritic cells are triggered by an allergen, signaling a potential immune reaction.

Identifying Chemical Sensitizers

This screening process is specifically designed to detect skin sensitizers—substances that cause allergic contact dermatitis.

The test is used to evaluate complex matrices like footwear textiles, looking for specific hazardous compounds such as acetophenone azine. By correlating marker expression with chemical exposure, manufacturers can identify unsafe materials before they reach the consumer.

Understanding the Scope and Specificity

Focus on Sensitization

It is critical to understand that the h-CLAT is highly specific to the immune activation pathway.

The test monitors the potential for skin sensitization (allergies) rather than direct tissue damage (irritation). It relies entirely on the upregulation of CD86 and CD54; if a chemical is toxic via a mechanism that does not trigger these specific dendritic cell markers, this particular test may not flag it.

Reliance on Surrogate Models

The test assumes that the response of the THP-1 monocytic cell line accurately mirrors the complex behavior of dendritic cells in the human body.

While effective for screening chemicals like acetophenone azine, the results are derived from an in vitro (cell-based) model. This provides a focused assessment of marker expression but remains a simulation of the actual human immune response.

Making the Right Choice for Your Project

The h-CLAT offers a precise method for screening textile safety without human or animal testing. Use these criteria to guide your application:

If your primary focus is Consumer Safety: Monitor CD86 and CD54 levels to ensure final footwear products do not trigger allergic immune responses.
If your primary focus is Material Compliance: Use the THP-1 cell line response to screen raw textiles specifically for the presence of sensitizers like acetophenone azine.

By isolating the expression of CD86 and CD54, the h-CLAT provides a definitive, quantifiable metric for predicting skin sensitization risks in footwear materials.

Summary Table:

Key Indicator	Biological Role	Measurement Method	Purpose in Footwear Testing
CD86	Cell surface protein	Flow Cytometry	Signals dendritic cell activation & sensitization
CD54	Adhesion molecule	Flow Cytometry	Monitors immune system response to chemical triggers
THP-1 Cell Line	Human monocytic cells	Cell Culture	Acts as a proxy for human dendritic cell behavior
Acetophenone Azine	Chemical Target	Chemical Screening	Detects specific hazardous sensitizers in textiles

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References

Isabelle Manière, Christophe Rousselle. Sensitization properties of acetophenone azine, a new skin sensitizer identified in textile. DOI: 10.1111/cod.14216

This article is also based on technical information from 3515 Knowledge Base .