Development of a non-radioactive endpoint in a modified local lymph node assay

Area of Science:

• Toxicology
• Immunology
• Dermatology

Background:

• The murine local lymph node assay (LLNA) is a cost-effective alternative to guinea pig models for contact sensitization testing.
• The standard LLNA uses radioactive materials, posing animal welfare concerns.
• Previous non-radioactive ex vivo assays could predict strong sensitizers but lacked sensitivity for moderate ones.

Purpose of the Study:

• To develop a more sensitive non-radioactive assay for predicting moderate contact sensitizers.
• To introduce a new parameter, the Corrected IL-2 Index (CII), for enhanced prediction accuracy.

Main Methods:

• An ex vivo assay based on LLNA principles was employed.
• Interleukin-2 (IL-2) release was measured in cell culture supernatants.
• The IL-2 release was corrected for lymph node weight ratio and CD4-positive subset ratio to calculate the CII.

Main Results:

• The Corrected IL-2 Index (CII) successfully predicted the allergenicity of moderate sensitizers, including OECD guideline-recommended substances like mercaptobenzothiazole and hexyl cinnamic aldehyde.
• The CII also accurately predicted the allergenicity of metal salts such as potassium dichromate, ammonium tetrachloroplatinate, and cobalt chloride.
• The enhanced sensitivity of the ex vivo method using CII allows for the detection of moderate sensitizers.

Conclusions:

• The Corrected IL-2 Index (CII) significantly enhances the sensitivity of non-radioactive ex vivo assays for contact sensitization testing.
• This improved method allows for the detection of moderate sensitizers, addressing a limitation of previous non-radioactive approaches.
• The CII offers a valuable tool for safer and more comprehensive contact sensitization testing, aligning with animal welfare principles.