mdash;: We characterized the relative biological activity and expression of two murine chemokines that may serve as functional homologues for human IL-8, KC, and macrophage inflammatory protein 2 (MIP2). Recombinant chemokines were produced in bacterial expression systems and antibodies specific for KC or MIP2 were raised. In vitro assays showed that KC elicited 4-fold greater neutrophil chemotaxis compared with MIP2, while MIP2 elicited significantly greater release of elastase. Lipopolysaccharide-(LPS) stimulated macrophages (8 h) secreted more MIP2 (approximately 10 ng/mL) compared with KC (approximately 4 ng/ml) and expression of either murine chemokine was independent of TNF [alpha] or IL-1 [beta] production. Thioglycollate (thio) and glycogen (gly) induced peritonitis produced more KC (thio= 7.1 and gly= 2.5 ng/mL) in the peritoneum compared with MIP2 (thio= 4.5 and gly= 0.3 ng/mL). Plasma KC levels were very high after either challenge (~ 24 ng/mL), which was> 50-fold more than the systemic increase in MIP2 (~ 0.3 ng/mL). Our data demonstrate that while KC and MIP2 have similar in vitro production characteristics, KC appears to be a more potent and systemically distributed chemokine during acute in vivo inflammation, while MIP2 expression appears limited to localized expression.