The popliteal lymph node assay: results of a preliminary interlaboratory validation study

Area of Science:

• Toxicology
• Immunology
• Pharmacology

Background:

• The popliteal lymph node (PLN) assay is a proposed method for predicting xenobiotic-induced autoimmune effects.
• Autoimmune reactions can be triggered by various chemical compounds, necessitating reliable predictive assays.

Purpose of the Study:

• To conduct a preliminary interlaboratory validation of the popliteal lymph node (PLN) assay.
• To assess the assay's ability to predict autoimmune-like reactions caused by specific xenobiotics.

Main Methods:

• Three laboratories blindly tested Wistar rats with four known autoimmune-inducing compounds (chlorpromazine, zimeldine, hydrazine, streptozotocin) and one negative control (barbital).
• Substances were administered via hind footpad injection, with popliteal lymph node (PLN) weight and cellularity measured on day 8.
• Weight and cellularity indices were calculated by comparing controlateral PLNs. Results were analyzed by a fourth laboratory.

Main Results:

• All four compounds known to cause autoimmune reactions were correctly identified by all three participating laboratories using both weight and cellularity indices.
• The negative control compound, barbital, consistently yielded negative results across all laboratories.
• While absolute values varied slightly between laboratories, these variations were not statistically significant.

Conclusions:

• The popliteal lymph node (PLN) assay demonstrated consistent and reliable detection of xenobiotics with potential autoimmune effects.
• The interlaboratory validation study provides strong evidence for the predictive value of the PLN assay in toxicology.
• The assay's performance suggests its utility in identifying compounds that may induce autoimmune responses in humans.