In vitro tests with sensitized lymphocytes-Relevance for predictive allergenicity testing.

The main obstacle to routine in vitro tests to identify contact sensitizers is the inappropriate application of the allergens in vitro, even when sufficient antigen-presenting cells are available. Some allergens may need the skin tissue for adequate conjugation with carrier molecules, whereas others may be poorly solubilized or toxic for the cultures. Methods, therefore, which make use of the in vivo system for allergen binding and presentation, but which assess in vitro the subsequent lymphocyte activation are most promising. For this reason, the local lymph node assay deserves more attention as a predictive assay in allergenicity testing and should be validated in more laboratories in the near future. The value of allergen-stimulated in vitro tests for predictive allergenicity screening will remain limited. This type of in vitro test is, however, invaluable for mechanistic studies on contact sensitivity in well defined allergen models. Also for clinical diagnosis of allergic contact sensitivity to selected allergens, the lymphocyte transformation test and macrophage migration inhibition test may be useful, particularly when skin tests fail to be conclusive.