An optimized lymphocyte blastogenesis assay for detecting the response of contact sensitized or photosensitized lymphocytes to hapten or photohapten modified antigen presenting cells

Abstract In vitro assays for predictive identification of contact sensitizers of photosensitizers are more quantifiable than current skin test methods and have the potential to reduce animal use. Mice were sensitized to various strong contact allergens, then an optimized lymphocyte blastogenesis assay was used for detecting the proliferation of lymph node lymphocytes from those mice in response to soluble antigen or hapten-modified antigen presenting cells in culture. In vivo sensitization to oxazolone (OXAZ), a prototype sensitizer, resulted in poor in vitro lymphocyte blastogenesis to a solubilized OXAZ preparation. To increase the assay sensitivity, dendritic cells from the draining lymph nodes of OXAZ-painted mice or OXAZ-modified Langerhans cell-enriched cultured epidermal cells (EC) were used as antigen presenting cells. This increased the OXAZ-specific response greater than 10-fold and 50-fold, respectively. This approach has since been used to demonstrate significant, albeit smaller, responses to weaker contact allergens such as nickel sulphate. EC were also used as antigen-presenting cells for in vitro lymphocyte blastogenesis assays designed to detect photoallergens. Lymphocytes from mice photosensitized to tetrachlorosalicylanilide (TCSA) showed a significantly increased response to EC previously photohapten-modified by treatment with TCSA plus ultraviolet A (UVA), as compared with lymphocytes cultured with EC treated with TCSA but no UVA. The lymphocyte blastogenesis assay may have potential as a predictive screen to identify contact and photocontact allergens.