IL-8 from local subcutaneous wounds regulates CD11b activation

The cellular and soluble mediators of a dermal inflammation can be studied by the skin chamber technique. The aim of this study was to address the physiological effect of soluble mediators, released into the skin chamber, with special focus on neutrophil CD11b activation. Mediators released at the inflammatory site were studied by Milliplex and enzyme-linked immunosorbent assay (ELISA) and correlated with transmigration and CD11b activation in vivo and in vitro. Transmigration was studied by the skin chamber technique and by the transwell method, and expression of the CBRM1/5 epitope on activated CD11b was analysed by flow cytometry following in vivo and in vitro incubation with chamber fluid or recombinant interleukin-8 (IL-8). Leucocyte in vivo and in vitro transmigration both correlated with the concentrations of IL-1β, tumour necrosis factor alpha (TNFα) and IL-8 at P < 0.05 (R > 0.7). Furthermore, CD11b was activated, in terms of exposure of the activation epitope, on neutrophils after 30 min of in vitro incubation with chamber fluid and correlated solely with the concentration of IL-8, P < 0.05 (R = 0.72). In vitro incubation with recombinant IL-8 confirmed a concentration-dependent expression of the activation epitope; however, induction of CBRM1/5 by recombinant IL-8 required a concentration that was significantly higher compared with that in chamber fluid. In addition, the CBRM1/5 epitope was analysed on in vivo extravasated neutrophils that displayed a significantly higher expression compared with circulating neutrophils, P = 0.04. We conclude that IL-8 is the major factor regulating the expression of CD11b activation epitope in neutrophils.