Migration of Langerhans cells from carcinogen-treated sheep skin

To define the mechanism(s) of carcinogen depletion of Langerhans cells (LC) from skin, the migration of LC from the skin to the regional lymph node was examined in carcinogen-treated, antigen-treated, and control sheep. This was assessed by cannulation of afferent lymphatic vessels that drain the treated areas of skin or the efferent lymphatic draining the regional lymph node. Cells draining from test or control skin were continuously collected and enumerated by indirect immunofluorescence and flow cytometry using specific anti-CD1 monoclonal antibodies. There was a marked increase in the rate of LC migration in the 8 h following the application of the contact sensitizing antigen trinitrochlorobenzene (TNCB). The chemical carcinogen 7,12-dimethylbenz(a)anthracene (DMBA) triggered a tenfold-greater migration of LC compared with TNCB--with the peak response at 5 d. After DMBA treatment LC were also detected in the efferent lymph of the regional lymph node. It is concluded that the depletion of LC from carcinogen-treated skin is due to the increased LC migration and not carcinogen-induced cell death.