THE POPLITEAL LYMPH-NODE ASSAY - RESULTS OF A PRELIMINARY INTERLABORATORY VALIDATION-STUDY

The popliteal lymph node (PLN) assay was proposed to predict possible autoimmune effects of xenobiotics. A preliminary interlaboratory valid ation study of the PLN assay was conducted in Wister rats. Three labor atories tested in blind fashion four compounds, namely chlorpromazine, zimeldine, hydrazine and streptozotocin, which were reported to cause autoimmune-like reactions in humans, and one compound, i.e. barbital, which was not, using strictly the same experimental procedure. All te sted substances were injected into the hind footpad of rats on day 1, and PLN weight and cellularity were measured on day 8. Comparison of t he controlateral PLN was used to calculate weight and cellularity indi ces. The results were independently analyzed in a fourth laboratory. A ll four positive compounds were detected by the three laboratories usi ng both weight and cellularity indices, and the negative compound cons istently proved negative. Despite variations in absolute values betwee n laboratories, although not significant, these results provide furthe r evidence of the potential predictive value of the PLN assay. (C) 199 7 Elsevier Science Ireland Ltd.