Adhesion of neutrophils to epidermal cells: prerequisites for and blocking by anti-CD11b antibodies

Immigration of neutrophils into the epidermis is a hallmark of several so-called neutrophilic dermatoses. In this study we used a frozen section adhesion assay to study the impact of different activation procedures as well as of CD11 integrins on cell-cell adhesion between neutrophils and epidermal cells. Serial sections from punch biopsies of healthy donors were incubated with freshly prepared neutrophils for 40 min and adherent cells were counted after washing. We found that preactivation of the biopsies with interferon-gamma in vitro is a prerequisite for neutrophil binding. Activation of neutrophils with N-formyl-methionyl-leucyl-phenylalanine (fMLP), tumor necrosis factor-alpha (TNF-alpha) or platelet activating factor (PAF) then leads to a three- to sixfold increase in neutrophil adhesion. This enhanced binding could be blocked by anti-CD11b monoclonal antibodies, whereas anti-CD11a and anti-CD11c antibodies exerted no significant effect. At a temperature of 6 degrees C, 50% inhibition of neutrophil binding was observed. Complement factor C3 and fibrinogen, known ligands for CD11b/CD18, could not be detected on epidermal cells by immunohistochemistry. In summary, our study showed that enhanced binding of neutrophils to epidermal sections can be achieved by prestimulation of both the keratinocytes with interferon-gamma and the neutrophils with fMLP, TNF-alpha and PAF. This adhesion was furthermore revealed to be dependent on the function of the leucocyte integrin CD11b/CD18.