PREDICTIVE IMMUNOTOXICOLOGICAL TEST SYSTEMS - SUITABILITY OF THE POPLITEAL LYMPH-NODE ASSAY IN MICE AND RATS

This article reviews results obtained with popliteal lymph node assays (PLNAs) in rodents and discusses their ability to detect and analyze immunotoxic effects of drugs and other low molecular weight (LMW) chem icals. In its basic form, the PLNA measures activation of the draining lymph node of the hind paw (i.e., the PLN) after injection of a test chemical into the hind foot pad. The assay appears to be appropriate t o recognize sensitizing, that is, allergenic and autoimmunogenic, chem icals, as well as nonsensitizing immunostimulatory chemicals. With mod ifications, PLNAs can detect immunosuppressive chemicals and distingui sh sensitizing from nonsensitizing chemicals. Furthermore, modified PL NAs enable detection of known as well as unknown sensitizing metabolit es, and may assist in the identification of the self-molecules that ac t as carriers for chemical sensitization or as targets of chemical-ind uced autoimmune disease. Experience with PLNAs shows that they are rap id, reproducible, and objective tests for recognition of sensitizing o r otherwise immunomodulating chemicals. Because current protocols of t oxicity testing are insensitive in predicting a chemical's potential t o result in immunomodulation, PLNAs, when further validated, may provi de welcome supplements to routine toxicity screening of chemicals, thu s enhancing chemical safety.