Heterologous desensitization of IL-8-mediated chemotaxis in human neutrophils by a cell-binding fragment of fibronectin.

In this study, we have explored the mechanism for the desensitization of IL-8-mediated neutrophil chemotaxis by a cell-binding fragment of fibronectin (120-kDa FN). Preincubation of neutrophil suspensions with the 120-kDa FN fragment resulted in a heterologous desensitization of IL-8-mediated chemotaxis while not affecting neutrophil chemotaxis to either fMLP or zymosan-activated serum. Preincubation of neutrophils with the beta1-integrin-activating antibody (TS2/16) mimicked the effects of the 120-kDa FN fragment while preincubating neutrophils with the beta1-integrin blocking antibody (mAb13) abrogated the inhibitory effects of the 120-kDa FN fragment on IL-8-mediated chemotaxis. Furthermore, we also demonstrated that the 120-kDa FN fragment did not inhibit chemotaxis to the CXC chemokine MGSA/GROalpha which interacts with high affinity to the IL-8 receptor B (CXCR2). By in vivo phosphorylation of neutrophils and probing lysates with an anti-CXCR1 antibody, we demonstrated that the addition of the cell-binding fragment of fibronectin resulted in a time-dependent phosphorylation of CXCR1. These findings suggest that the mechanism of heterologous desensitization of IL-8-mediated chemotaxis following ligation of FN-dependent integrins is the result of phosphorylation of the CXCR1 receptor.