Functional and phenotypic analysis of isolated human Langerhans cells and indeterminate cells

In the mixed skin cell lymphocyte culture reaction (MSLR), epidermal cells induce the proliferation in vitro of peripheral blood lymphocytes. Using monoclonal antibodies (MCAB) OKT6 specific for Langerhans cells among epidermal cells and an anti HLA-Dr, we analysed which epidermal cells are necessary in MSLR in man. Inhibition and reduction of the proliferative responses in MSLR conducted respectively with 'anti HLA-Dr and complement' and 'OKT6 and complement'-pretreated epidermal cells suggested that not only Langerhans cells but also other HLA-Dr bearing cells play a major role. Immuno-electron microscopic studies of either HLA-Dr (+) or OKT6 (+) enriched and depleted epidermal cells suspensions: (I) were well correlated with results in MSLR; (2) indicated that Langerhans cells express both T6 and HLA-Dr determinants while indeterminate cells express only the HLA-Dr. No other epidermal cells were found to be either OKT6 or HLA-Dr (+). The data strongly suggest that not only Langerhans cells but also OKT6 (-) HLA-Dr (+) indeterminate cells play a major role in lympho-epidermal interactions.