Jacobs, J., C. Lehe, K. Cammans, K. Yoneda, P. Das, and G. Elliott. Automated Quantification of Langerhans Cell Migration from Human Organotypic Skin Explant Culture. ATLA 1999. 27: 116.

Human skin, obtained with the consent of patients undergoing cosmetic surgery, can be used in vitro to screen for potential contact sensitisers (human skin explant sensitisation assay [huSESA]). When painted on skin in vitro, contact sensitisers accelerate the migration of Langerhans cells (LCs) out of the epidermis. Using standard contact sensitisers and controls, we characterized the information obtained when monoclonal antibodies (mAbs) to MHC II, CD1a and Birbeck granules (Lag) were used to stain human LCs in the epidermis. After culture for 24 hours, the number of epidermal LCs strongly decreased in skin painted with strong contact sensitisers, shown by all three mAbs. Occasionally, LCs could be found in the dermis, possibly passing it while migrating out of the skin explant. Double staining showed that all LCs, whether in untreated dermis or epidermis, reacted with both anti-Lag and anti-CD1a antibodies. These results make selective down-regulation of LC markers in the epidermis in huSESA unlikely. In contrast to the CD1a staining pattern, which showed the full dendrites of LCs, the lag antibody staining was more confined to the LC body. The LCs’ dendrites form a network within epidermis, thus making automatic detection of individual cells difficult. Using software-aided quantification of anti-Lag stained immunohistochemistry slides, we were able to set up an automated system for quantifying the migration of LCs in this in vitro model, for screening for putative contact sensitisers.