DIETARY VITAMIN-A ENHANCES SENSITIVITY OF THE LOCAL LYMPH-NODE ASSAY

Murine assays such as the mouse ear swelling test (MEST) and the local lymph node assay (LLNA) are popular alternatives to guinea pig models for the identification of contact sensitizers, yet there has been con cern over the effectiveness of these assays to detect weak and moderat e sensitizers, Much work has been done to improve the sensitivity of t he MEST, including the addition of a vitamin A acetate (VAA) enriched diet, which increases its sensitivity, Vitamin A acetate has been repo rted to increase the numbers of Langerhans cells (antigen presenting c ells) in the skin, which could in turn enhance the cellular immune res ponse, Because the LLNA relies on tritiated-thymidine incorporation by proliferating T cells during the induction phase, we have studied the potential of the VAA diet to enhance sensitivity of the LLNA, Results indicate that the VAA enriched diet significantly increased the LLNA sensitivity to formalin, eugenol, glutaraldehyde, trimellitic anhydrid e, and an azo dye at concentrations where no proliferation was observe d in mice maintained on the standard diet. Maintenance on a VAA diet f or 3 weeks prior to initiating the sensitization procedure was optimal , Thus, incorporation of a VAA diet improves the sensitivity of the LL NA as a quick, objective, and relatively inexpensive screen for detect ing moderate and weak contact sensitizers.