Studies on polymorphonuclear leukocyte bactericidal function III: the role of extracellular matrix proteins.

We investigated the effect of the extracellular matrix proteins fibronectin (Fn) and laminin (Ln) on polymorphonuclear leukocytes (PMN) bactericidal activity. Adherence of PMN to increasing concentrations of Ln significantly increased the killing of Escherichia coli after 240 min of adherence, while fibronectin significantly increased PMN staphlacidal activity after 240 min of adherence. The addition of IL-1beta and IL-8 but not TNF-alpha increased PMN bactericidal activity against E. coli when PMN were adhered to Ln, while TNF-alpha and IL-8 increased PMN bactericidal activity against Staphylococcus aureus when PMN were adhered to Ln. TNF-alpha increased PMN killing of E. coli when PMN were adhered to Fn, while only IL-1beta increased the killing of S. aureus when PMN were adhered to FN. Anti-VLA-3 (alpha3/beta1) monoclonal antibodies (mAbs) inhibited the effect of Ln on PMN bactericidal activity, while anti-VLA-5 (alpha5/beta1) mAbs inhibited the effect of Fn on PMN bactericidal activity. Progressive cross-linkage of these two receptors led to a dose-dependent reduction in PMN bactericidal activity for both pathogens when PMN were adhered to Ln or Fn, respectively. These results demonstrate that extracellular matrix proteins +/- exogenously added cytokines have the capacity to regulate PMN bactericidal activity. The signals sent by these matrix proteins to increase PMN bactericidal activity are transduced primarily via separate alpha subunits of the beta1 integrin complex. Stimulation of these receptors might lead to potential upregulation of PMN bactericidal activity which would be potentially advantageous in vivo at sites of infection.