IN-VITRO PRIMARY SENSITIZATION OF HAPTEN-SPECIFIC T-CELLS BY CULTUREDHUMAN EPIDERMAL LANGERHANS CELLS - A SCREENING PREDICTIVE ASSAY FOR CONTACT SENSITIZERS

Background The need to develop predictive tests which could identify p otential allergens has been recognized for many years. There is as yet no accepted in vitro method for the assessment of contact sensitizers . Objective We have tested the ability of a range of contact allergens to induce in vitro primary sensitization of autologous T cells. Metho d T-cell proliferation induced by haptens using 2-day cultured human L angerhans cells as antigen-presenting cell was assessed by H-3 thymidi ne incorporation. Antigen specific stimulation was calculated as stimu lation indexes. Results Strong allergens induced in vitro a primary T- cell response in all (trinitrophenyl, TNP: 13/13) or in the majority ( fluorescein isothiocyanate, FITC: 7/10) of experiments. An irritant, s odium dodecyl sulfate (SDS), failed to generate a significant T-cell p roliferation in any of the experiments (0/10). We obtained a significa nt lymphoproliferative response to weak sensitizers only in a limited number of experiments: (coumarin: 1/12, citronellal: 0/10, hydroxycitr onellal: 2/8), p-Phenylenediamine (PPDA), a prohapten and highly sensi tizing chemical in vivo, generated primary sensitization in vitro in o nly one of six experiments, while Bandrowski's base (BB), a metaboliza tion product of PPDA induced a significant T-cell response in all six experiments. Conclusion The present in vitro model allows discriminati on between two groups of substances: strong contact sensitizers (TNP, FITC, BB) on the one hand and weak sensitizers (coumarin, citronellal and hydroxycitronellal) and irritants (SDS) on the other hand. It coul d be used as a screening in vitro assay to eliminate strong contact al lergens before further predictive animal tests have to be performed.