Endogenous modulators of inflammatory cell recruitment.

Leukocyte recruitment is a central immune process. Multiple factors have been described to promote leukocyte infiltration into inflamed tissues, but only recently has evidence for endogenous negative modulators of this inflammatory process emerged. The discovery of several locally produced modulators has emerged into a new field of endogenous inhibitors of leukocyte extravasation. Recent findings from several inflammatory disease models show that tissues can self-regulate the recruitment of inflammatory cells, suggesting that local tissues may have a greater 'regulatory say' over the immune response than previously appreciated. Here, we propose that locally produced modulators of leukocyte recruitment may represent local homeostatic mechanisms that tissues and organs may have evolved for protection against the destructive potential of the immune system.