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 cells. Sections were prepared from small punch biopsies from healthy donors after preincubation with IFN-gamma. Freshly prepared neutrophils were activated 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 adhesion was achieved at a concentration of 10 mu g/ml, Colchicine at concentrations of 10-200 ng/ml inhibited neutrophil binding with a clear correlation between inhibition and colchicine concentration. At a colchicine concentration of 110 ng/ml, 50% blocking was achieved. Since the function of CD11b/ CD18 is necessary for neutrophil adhesion in this assay, we monitored CD11b expression on neutrophils after dapsone and colchicine exposure. CD11b expression on neutrophils was significantly reduced 5 h after incubation with dapsone 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 significantly inhibited adhesion between neutrophils and the epidermis.