In vitro mixed skin cell lymphocyte culture reaction (MSLR) in man: analysis of the epidermal cell and T cell subpopulations.

The nature of normal human epidermal cells (EC) and peripheral blood (PB) cells that react in vitro in allogeneic mixed skin cell lymphocyte culture reaction (MSLR) was investigated using monoclonal antibodies (MCAB) specific for cell subpopulations. T cells and helper-inducer and suppressor-cytotoxic T cell subsets were defined by OKT3, OKT4, OKT8 MCAB, respectively, whereas, among EC, Langerhans cells were characterized by reactivity with OKT6 or anti-HLA-DR MCAB. MSLR were conducted with untreated cell suspensions as controls and cells suspensions depleted of various functionally active cell subset(s). Two approaches were used for cell depletion: (1) complement (C')-mediated lysis by MCAB of T cells, T cell subsets, HLA-DR or OKT6 positive cells; (2) panning of PB cells or EC after pre-incubation with the appropriate MCAB to deplete or enrich (OKT6) cell suspensions with the respective cell subset. Responses in MSLR were abolished after treatment of PB cells with OKT3 + C' or OKT4 + C', significantly reduced with OKT8 + C'; they were abolished after incubation of EC with anti-HLA-DR + C' and significantly reduced with OKT6 + C'. After panning, OKT3 and OKT4 depleted populations did not proliferate in MSLR while OKT8 depleted populations respond as controls. OKT6 depleted EC were not able to stimulate PB cells, yet proliferation rates were increased after stimulation by OKT6 enriched EC. Data show that helper-inducer T cells (OKT3+; OKT4+) play the major role in MSLR and that the presence of Langerhans cells is necessary for the stimulation of PB cells. They also suggest that co-operation between helper and suppressor cells is necessary for an optimal response. Differences in results using either OKT6 or anti-HLA-Dr-C'-mediated treatment of EC may be related to differences in the cellular expression of these markers by EC.