Langerhans cell--mononuclear cell contacts are not specific for allergy in patch tests.

Langerhans cell-mononuclear cell contacts in the epidermis were analysed in minimum positive allergic and toxic patch tests after 6, 12, 24, 48, and 72 hours. No differences between allergic and toxic patch tests were observed in the appearance of Langerhans cells or in the number of Langerhans cell-mononuclear cell contacts. Thus, Langerhans cell-mononuclear cell contacts are not specific for contact allergic reactions, as has previously been suggested.