One reported weakness of the murine Local Lymph Node Assay (LLNA) is its inability to differentiate weak sensitizers and strong irritants. In these studies, we evaluated a panel of irritants and weak to moderate sensitizers in a modified LLNA and an irritancy/phenotypic analysis assay. Compounds initially tested included p-xylenol, thiomerosal, formaldehyde, benzocaine, menthol, and phenol. The LLNA protocol was modified to include pre and post ear measurements as an indication of irritation, The irritancy/phenotypic analysis method also used ear swelling as an indication of irritancy but evaluated sensitization by an elevation of the %B220+ and/or %IgE+B220+ (1gB-mediated) draining lymph node cell populations. In both assays, female BALB/c mice were topically exposed on the ear pinnae for 4 consecutive days. Ear measurements were taken prior to exposure on day 1 and 24 hr after final exposure on day 5. For the LLNA, [lH]-thymidine incorporation was measured on day 5 and for phenotypic analysis cell populations were examined on day 10. Consistent with the human literature, thiomerosal and formaldehyde were identified as irritants and sensitizers in both the modified LLNA and the irritancy/phenotypic assay. Additionally, the IgE+B220+ lymph node cell population was elevated in animals exposed to formaldehyde in agreement with reports of human contact urticaria following exposure to this compound. Phenol, a strong human irritant with a low sensitization index, was positive for irritation and sensitization in these assays. Benzocaine gave a false negative response for sensitization in both assays when tested at a 50% concentration in acetone. Although reported to be human irritants, menthol (50%), and p-xylenol (10%) were negative for both irritation and sensitization at the highest concentrations tested.
Toxins; Toxicology; Toxic-materials; Laboratory-animals; Animal-studies; Statistical-analysis; Analytical-chemistry; Analytical-methods; Chemical-analysis; Dose-response; Exposure-assessment; Lymph-nodes; Lymphatic-system; Irritants; Sensitivity-testing; Sensitization; Ears; Cellular-function; Cell-function; Cell-cultures
The Toxicologist. Society of Toxicology 38th Annual Meeting, March 14-18, 1999, New Orleans, Louisiana