Dapsone and colchicine inhibit adhesion of neutrophilic granulocytes to epidermal sections

A frozen section adhesion assay was used to study the influence of dapsone and colchicine on cell-cell adhesion between neutrophils and epidermal cell s. Sections were prepared from small punch biopsies from healthy donors aft er preincubation with IFN-gamma. Freshly prepared neutrophils were activate d with TNF-alpha or PAF after exposure to dapsone or colchicine, incubated on these sections, and the adhered cells mere enumerated after washing. In the presence of dapsone (at concentrations of 0.1-80 mu g/ml) adherence of neutrophils could be blocked dose-dependently and 50% inhibition of adhesio n was achieved at a concentration of 10 mu g/ml, Colchicine at concentratio ns of 10-200 ng/ml inhibited neutrophil binding with a clear correlation be tween inhibition and colchicine concentration. At a colchicine concentratio n of 110 ng/ml, 50% blocking was achieved. Since the function of CD11b/ CD1 8 is necessary for neutrophil adhesion in this assay, we monitored CD11b ex pression on neutrophils after dapsone and colchicine exposure. CD11b expres sion on neutrophils was significantly reduced 5 h after incubation with dap sone at a concentration of 80 mu g/ ml, whereas no effects of colchicine on CD11b expression could be demonstrated. Our study showed that both drugs s ignificantly inhibited adhesion between neutrophils and the epidermis.