Chemokine networks in vivo: involvement of C-X-C and C-C chemokines in neutrophil extravasation in vivo in response to TNF-alpha

Abstract

In this study, we have evaluated the role of specific chemotactic cytokines in leukocyte recruitment to s.c. tissue in response to TNF-alpha in vivo. Injection of TNF-alpha into s.c. air pouches led to a rapid, transient accumulation of leukocytes. Maximal accumulation of leukocytes in the air pouch was observed at between 2 and 4 h after injection of TNF-alpha. The cellular exudate comprised predominantly neutrophils, with smaller numbers of eosinophils and mononuclear phagocytes also being recruited. However, lymphocyte recruitment was not observed. TNF-alpha injection induced a time-dependent increase in the levels of immunoreactive macrophage inflammatory protein (MIP)-2, MIP-1alpha, and JE in the pouch exudate as well as increased steady-state mRNA levels of KC, MIP-2, MIP-1alpha, and JE in the tissue lining the s.c. pouch and of MIP-2, MIP-1alpha, and JE in the exudate cell population. Passive immunization with specific Abs directed against each of these chemokines significantly inhibited the accumulation of neutrophils, mononuclear phagocytes, and eosinophils in response to TNF-alpha. Taken together, these data demonstrate the existence of a chemokine network in vivo involving at least four individual chemokines that regulates recruitment of the major peripheral blood granulocytes and mononuclear phagocytes to s.c. sites during acute inflammation. To our knowledge, these data are also the first demonstration that the C-C chemokine JE is involved in neutrophil recruitment in a physiologic system in vivo.